Advances in Electrical and Electronic Engineering - fast.vsb.cz

The 3rd International Conference

on Sustainable Development in Civil,

Urban and Transportation Engineering

2020

Book of Abstracts

October 21-23, 2020

Ostrava, Czech Republic

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The 3rd International Conference on Sustainable Development in

Civil, Urban and Transportation Engineering 2020. Book of Abstracts

ISBN 978-80-248-4457-2

CD-ROM

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Information for participants

The conference sessions are on-line because of COVID-19 emergency. All conference papers

are included in this book.

There are four on-line sessions and a poster session. All on-line sessions will be organised with

the use of the Google Meet service. The invitation links are listed below.

Conference Inauguration

• Date: Wednesday, October 21, 2020

• Time: 9:00-9:30 Central European Summer Time

• Google Meet: https://meet.google.com/ddq-zypo-xue

• Chairs: Radim Cajka, Minh Tran Tung

Conference Sections

Urban Planning; Modern and Sustainable Architecture

• Date: Wednesday, October 21, 2020



• Chairs: Ngo Le Minh, Stanislav Endel

• Invited lecture: professor Tomoya Kaji

Modelling in Mechanics

• Date: Thursday, October 21, 2020



• Chairs: Do Nguyen Van Vuong, Tomasz Ponikiewski, Petr Konecny

https://meet.google.com/ddq-zypo-xue



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Modern Buildings and Engineering Constructions



• Google Meet: https://meet.google.com/jsi-qdos-fez

• Chairs: Le Duc Hien, Miroslav Rosmanit

• Invited lecture: dr. Pavlina Mateckova

Modern and Renewable Building Materials



• Google Meet: https://meet.google.com/jsi-qdos-fez

• Chairs: Bui Quoc Bao, Miroslav Rosmanit

• Invited lecture: associate professor Bui Quoc Bao

Poster Session

• Date: Friday, October 23, 2020


Conference End

• Date: Friday, October 23, 2020


https://meet.google.com/jsi-qdos-fez

https://meet.google.com/jsi-qdos-fez

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List of on-line presentations


1. Invited lecture: Tomoya KAJI, METROPOLITAN SUSTAINABILITY AND TRANSIT

ORIENTED DEVELOPMENT OF TOKYO

2. Stanislav ENDEL, POSSIBILITIES OF HOUSES VALUATION AUTOMATION IN THE CZECH

REPUBLIC

3. Beisi JIA, Sibei LIU, Michelle NG, AIR QUALITY AND MORPHOLOGICAL

CHARACTERISTICS FOR HEALTHY LIVING COMMUNITY IN SHENZHEN

4. Adéla BRÁZDOVÁ, Barbara VOJVODÍKOVÁ, Jiří KUPKA, METHODOLOGY OF GREEN

ACUPUNCTURE AS A TOOL FOR SUSTAINABLE STRATEGY IN URBAN PLANNING

5. Le-Minh NGO, Duy Anh TRINH, Hai-Yen HOANG, RESEARCH ON ADAPTATION

SOLUTIONS TO HIGH TIDE FOR POOR HOUSING IN HO CHI MINH CITY

Modern Buildings and Engineering Constructions

1. Invited lecture: Pavlina MATECKOVA, Oldrich SUCHARDA, Vlastimil BÍLEK, Lucie MYNARZOVA, COMPLEX DESIGN OF BEAMS MADE OF HIGH PERFORMANCE

CONCRETE

2. Duc-Hien LE, Khanh-Hung NGUYEN, Quoc-Dung TRUONG, PRELIMINARY STUDY ON

BENDING STRENGTH OF RECYCLED AGGREGATE CONCRETE BEAMS

3. Dang Bao Tran, COMPARISON OF STRESS FIELD AND STRUT-AND-TIE ANALYSES

4. Miroslav ROSMANIT, Anežka MACHALOVÁ, REAL BEHAVIOR OF END-PLATE BOLT

CONNECTIONS OF TENSIONED PROFILES

5. Marie KOZIELOVA, Lucie MYNARZOVA, Petr MYNARCIK, EXPERIMENTAL TESTING OF

MASONRY SUBJECTED TO CONCENTRATED LOAD IN THE DIRECTION OF BED JOINTS

6. Pavel DOBEŠ, Antonín LOKAJ, LOAD-CARRYING CAPACITY OF BOLTED CONNECTIONS

OF ROUND TIMBER WITH DIFFERENT DISTANCES BETWEEN THE FASTENER AND THE

LOADED END

7. Vuong Nguyen Van DO, Le Dang Minh TU, FINITE ELEMENT APPROACH ON DYNAMIC

RESPONSE OF EULER-BERNOULLI BEAM SUBJECTED TO MOVING VEHICLES

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1. Invited lecture: Quoc-Bao BUI, Hoai Bao LE, Thanh-Phong NGO, Duc-Hien LE, Minh-

Tung TRAN, To-Anh-Vu PHAN, DIFFERENT APPROACHES TO RECYCLE WASTES FOR

CONSTRUCTION MATERIAL PRODUCTION

2. Tung M. TRAN, Thong M. PHAM, RESPONSE OF LIGHTWEIGHT RUBBERIZED

CONCRETE UNDER IMPACT LOAD

3. Monika KUBZOVA, Vit KRIVY, DURABILITY AND RELIABILITY OF THE WEATHERING

STEEL INFLUENCED BY CHLORIDES

4. Hai Viet VO, SENSITIVITY OF FACTORS INFLUENCING DYNAMIC MODULUS OF

ASPHALT CONCRETE

5. Dawid GIEROŃ, Tomasz PONIKIEWSKI, Jakub AUGUSTYN, CEMENTITIOUS BINDER

MORTARS PRINTING TECHNOLOGY – 3D PRINTER CONSTRUCTION

6. Viktor DUBOVSKÝ, Dagmar DLOUHÁ, EVAPORATION ESTIMATES


1. Milan HOLICKY, RELIABILITY APPROACHES AFFECTING SUSTAINABILITY IN

CONSTRUCTION

2. Miroslav SÝKORA, Jan MLČOCH, Pavel RYJÁČEK, UNCERTAINTY IN NDT

ASSESSMENTS OF HISTORIC STEEL BRIDGES

3. Daniel JINDRA, Petr HRADIL, Jiří KALA, Petr KRÁL, THE SUITABLE DISCRETIZATION

OF CONCRETE PLATE FINITE ELEMENT MODEL EXPOSED TO HIGH VELOCITY

LOADING

4. Lukáš POSPÍŠIL, Martin ČERMÁK, David HORÁK, Jakub KRUŽÍK, NON-MONOTONE

PROJECTED GRADIENT METHOD IN LINEAR ELASTICITY CONTACT PROBLEMS WITH

GIVEN FRICTION

5. Tomas NOVOTNY, USING 3D SCAN FOR STEEL STRUCTURE SURVEYS

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List of abstracts


01 Agnieszka KOCOT, Tomasz PONIKIEWSKI. INFLUENCE OF SURFACE MODIFICATION

OF ARTIFICIAL WASTE ON STRENGTH OF CEMENTITIOUS COMPOSITE

02 Daniel JINDRA1, Petr HRADIL, Jiří KALA, Petr KRÁL. THE SUITABLE DISCRETIZATION OF

CONCRETE PLATE FINITE ELEMENT MODEL EXPOSED TO HIGH VELOCITY LOADING

03 Ivan KOLOŠ, Vladimíra MICHALCOVÁ and Lenka LAUSOVÁ. AERODYNAMIC

CHARACTERISTICS OF THE CYLINDER IN SUBCRITICAL AND CRITICAL REGIME

04 Jakub FLODR, Petr LEHNER, Martin KREJSA. NUMERICAL MODEL OF TENSILE TEST OF

STEEL S390D USED IN THIN-WALLED STRUCTURES

05 Jorge Álvarez Morán, Stanislav Seitl, Petr Miarka. 3D NUMERICAL CALCULATION OF

STRESS INTENSITY FACTOR ON I-PROFILE BEAM UNDER THE BENDING LOAD

06 Juraj KRÁLIK, Juraj KRÁLIK, jr. PROBABILISTIC ASSESSMENT TO DETERMINE

SEISMIC LOAD CONSIDERING THE LOCAL SITE EFFECTS

07 Lukáš POSPÍŠIL, Martin ČERMÁK, David HORÁK, Jakub KRUŽÍK. NON-MONOTONE

PROJECTED GRADIENT METHOD IN LINEAR ELASTICITY CONTACT PROBLEMS WITH GIVEN

FRICTION

08 Marie HORNAKOVA, Tuan D. LE, Petr LEHNER, Petr KONECNY. EVALUATION OF

DIFFUSION COEFFICIENT BASED ON CHLORIDE PROFILE AND ELECTRICAL RESISTIVITY OF

WASTE AGGREGATE CONCRETE

09 Martin KREJSA, Jiri BROZOVSKY, Jiri KOKTAN. PREDICTION OF FATIGUE DAMAGE

BASED ON PARALLEL ALGORITHM

10 Michaela BOBKOVÁ, Lukáš POSPÍŠIL. COMPARISON OF DIFFERENT SUPPORT

TYPES IN BENDING PROBLEM OF THE BEAM

11 Michal VYHLÍDAL, Jan KLUSÁK. A CRACK APPROACHING THE EDGE OF THE

AGGREGATE

12 Milan HOLICKY. RELIABILITY APPROACHES AFFECTING SUSTAINABILITY IN

CONSTRUCTION

13 Miroslav SÝKORA, Jan MLČOCH, Pavel RYJÁČEK. UNCERTAINTY IN NDT

ASSESSMENTS OF HISTORIC STEEL BRIDGES

14 Nela FREIHERROVÁ, Martin KREJSA. BIAXIAL TESTING PROCEDURE OF TEXTILE

MATERIALS IN MEMBRANE STRUCTURES

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15 Tereza JUHÁSZOVÁ, Petr MIARKA, Stanislav SEITL, Ildikó MERTA. NON-TRADITIONAL

GEOMETRY OF WEDGE-SPLITTING TEST

16 Tomasz PONIKIEWSKI, Dawid GIEROŃ, Jakub AUGUSTYN. CEMENTITIOUS BINDER

MORTARS PRINTING TECHNOLOGY – 3D PRINTER CONSTRUCTION

17 Veronika VALASKOVA, Jozef VLCEK. INTRODUCTION TO FIRST APPROACH OF

DETERMINATION OF SMALL SCALE PHYSICAL MODEL PARAMETERS OF PAVEMENT

18 Vladimíra MICHALCOVÁ, Kamila KOTRASOVÁ. INFLUENCE OF NUMERICAL

DIFFUSION ON CFD SIMULATION PRECISION OF VELOCITY AND TEMPERATURE FIELD


19 Hai Viet VO. SENSITIVITY OF FACTORS INFLUENCING DYNAMIC MODULUS OF

ASPHALT CONCRETE

20 Monika KUBZOVA, Vit KRIVY. DURABILITY AND RELIABILITY OF THE WEATHERING

STEEL INFLUENCED BY CHLORIDES

21 Quoc-Bao BUI, Hoai Bao LE, Thanh-Phong NGO, Duc-Hien LE, Minh-Tung TRAN, To-Anh-

Vu PHAN. DIFFERENT APPROACHES TO RECYCLE WASTES FOR CONSTRUCTION MATERIAL

PRODUCTION

22 Tung M. TRAN, Thong M. PHAM. RESPONSE OF LIGHTWEIGHT RUBBERIZED

CONCRETE UNDER IMPACT LOAD

23 Viktor DUBOVSKÝ, Dagmar DLOUHÁ. EVAPORATION ESTIMATES

24 Vlastimil BILEK, David BUJDOS, Oldrich SUCHARDA. SOME PROPERTIES OF

ALKALI-ACTIVATED MATERIALS

Modern Buildings and Egineering Constructions

25 Antonin LOKAJ, Pavel DOBES and Kristyna VAVRUSOVA. STIFFNESS AND

DEFORMATION ANALYSIS OF CLT PANELS

26 Dang Bao Tran. COMPARISON OF STRESS FIELD AND STRUT-AND-TIE ANALYSES

27 Duc-Hien LE, Khanh-Hung NGUYEN, Quoc-Dung TRUONG. PRELIMINARY STUDY ON

BENDING STRENGTH OF RECYCLED AGGREGATE CONCRETE BEAMS

28 Jaroslav SOLAŘ. WALL CAVITIES BY WET MASONRY REHABILITATION

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29 Lukas DURIS, Eva Hrubesova. ADVANCED MODELLING OF THE INTERACTION

BETWEEN THE FOUNDATION STRUCTURE AND THE SUBSOIL

30 Marek JOHANIDES, Lenka KUBÍNCOVÁ, Antonín LOKAJ, David MIKOLÁŠEK. ANALYSIS

OF THE TIMBER FRAME CONNECTION WITH DOWEL TYPE MECHANICAL METAL FASTENERS

31 Marie KOZIELOVA, Lucie MYNARZOVA, Petr MYNARCIK. Experimental Testing of

Masonry Subjected to Concentrated Load in the Direction of Bed Joints

32 Miroslav ROSMANIT. ELASTIC POST-BUCKLING BEHAVIOR OF PLATES WITH AN

INTERMEDIATE STIFFENER – TWO-STRIP MODEL SOLUTION

33 Miroslav ROSMANIT, Anežka MACHALOVÁ. REAL BEHAVIOR OF END-PLATE BOLT

CONNECTIONS OF TENSIONED PROFILES

34 Pavel DOBEŠ, Antonín LOKAJ. LOAD-CARRYING CAPACITY OF BOLTED

CONNECTIONS OF ROUND TIMBER WITH DIFFERENT DISTANCES BETWEEN THE FASTENER

AND THE LOADED END

35 Pavlina MATECKOVA, Oldrich SUCHARDA, Vlastimil BÍLEK, Lucie MYNARZOVA. DESIGN

OF STRUCTURAL ELEMENTS MADE OF NEW VARIANTS OF CONCRETE WITH REGARD TO

SUSTAINABILITY

36 Petr MYNARCIK, Jiri KOKTAN, Ondrej MILLER. EXPERIMENTAL TESTING OF POST-

TENSIONED INDUSTRIAL FLOOR MODELS

37 Radim CAJKA, Marie KOZIELOVA, Zuzana MARCALIKOVA, Pavlina MATECKOVA, Oldrich

SUCHARDA. ANALYSIS AND EXPERIMENTAL TESTING OF FIBRE REINFORCEMENT CONCRETE

SLABS IN INTERACTION WITH SUBSOIL

38 Tomas NOVOTNY. USING 3D SCAN FOR STEEL STRUCTURE SURVEYS

39 Tomasz HOWIACKI. DISTRIBUTED FIBRE OPTIC SENSORS IN CIVIL ENGINEERING

APPLICATIONS – SELECTED CASE STUDIES IN POLAND

40 Vuong Nguyen Van DO. FREE VIBRATION ANALYSIS OF FUNCTIONALLY GRADED

MATERIAL PLATES USING MK MESHFREE METHOD WITH A SIMPLE KIRCHHOFF PLATE THEORY

41 Vuong Nguyen Van DO, Le Dang Minh TU. FINITE ELEMENT APPROACH ON DYNAMIC

RESPONSE OF EULER-BERNOULLI BEAM SUBJECTED TO MOVING VEHICLES

42 Zdenka NEUWIRTHOVA, Radim CAJKA. NONLINEAR MODEL OF SOIL-SLAB

INTERACTION

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43 Beisi JIA, Sibei LIU, Michelle NG. AIR QUALITY AND MORPHOLOGICAL

CHARACTERISTICS FOR HEALTHY LIVING COMMUNITY IN SHENZHEN

44 Dagmar KUTA, Marek TEICHMANN, Stanislav ENDEL, Lucie HURDALKOVA. “URBAN –

SPRAWL” AS AN ASPECT DAMAGING SUSTAINABLE URBAN DEVELOPMENT - THE

BACKGROUND OF THE PHENOMENON ON THE EXAMPLE OF THE CZECH REPUBLIC

45 Adéla BRÁZDOVÁ, Barbara VOJVODÍKOVÁ, Jiří KUPKA. METHODOLOGY OF GREEN

ACUPUNCTURE AS A TOOL FOR SUSTAINABLE STRATEGY IN URBAN PLANNING

46 Ivana MAHDALOVA, Vaclav SKVAIN. OCCURRENCE OF VEHICLES BUNCHES IN TRAFFIC

FLOW

47 Jan PETRU, Vladislav KRIVDA. GEOMETRIC ANALYSIS OF TURBO ROUNDABOUT

ENTRANCE

48 Le-Minh NGO, Duy Anh TRINH, Hai-Yen HOANG. RESEARCH ON ADAPTATION

SOLUTIONS TO HIGH TIDE FOR POOR HOUSING IN HO CHI MINH CITY

49 Le-Minh NGO, Phuong-Thao HOANG-THI. URBANIZATION OF PERI-URBAN AREA -

THE PROBLEM OF MAJOR ASIAN CITIES. CASE STUDY OF NHA BE DISTRICT, HO CHI MINH CITY

50 Marek TEICHMANN, Dagmar KUTA, Stanislav ENDEL, Natalie SZELIGOVA, Frantisek

KUDA. MODELLING AND OPTIMISATION OF THE DRINKING WATER SUPPLY NETWORK –

A SYSTEM CASE STUDY FROM THE CZECH REPUBLIC

51 Michal FALTEJSEK, Frantisek KUDA. THE EFFECT OF ORIENTATION AND LOCATION OF

BUILDINGS IN URBAN AREAS ON THE THERMAL STABILITY OF BUILDINGS

52 Miloslav ŘEZÁČ, Leopold HUDEČEK, Otto ROHÁČ, Denisa CIHLÁŘOVÁ. POSSIBILITIES

OF USE THE RAIL SIDING TRACKS AFTER FINISHING MINING ACTIVITIES

53 Ondřej JURAČKA, Klára FROLÍKOVÁ PALÁNOVÁ. THE IMPACT OF SOCIAL

PERCEPTION ON THE CONDITION OF CEMETERIES

54 Stanislav ENDEL, Marek TEICHMANN, Dagmar KUTÁ. POSSIBILITIES OF HOUSES

VALUATION AUTOMATION IN THE CZECH REPUBLIC

55 Tomoya KAJI. METROPOLITAN SUSTAINABILITY AND TRANSIT ORIENTED

DEVELOPMENT OF TOKYO

56 Tu Anh TRINH, Linh Phuong Thi LE. URBAN TRAFFIC EMISSION AND POTENTIAL

BEHAVIOURAL-TECHNOLOGICAL SOLUTION

57 Vaclav BERAN, Marek TEICHMANN, Frantisek KUDA, Natalie SZELIGOVA. DECISION

MAKING RULES AND THE INFLUENCE OF MEMORY DATA

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58 Vaclav BERAN, Marek TEICHMANN, Frantisek KUDA, Renata ZDARILOVA, Natalie

SZELIGOVA. DYNAMICS OF REGIONAL DEVELOPMENT IN REGIONAL AND MUNICIPAL

ECONOMY

59 Vladislav KRIVDA, Jan PETRU, David MACHA, Kristyna PLOCOVA, David FIBICH.

AN ANALYSIS OF TRAFFIC CONFLICTS AS A TOOL FOR SUSTAINABLE ROAD TRANSPORT

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THE 3RD INTERNATIONAL CONFERENCE ON SUSTAINABLE DEVELOPMENT IN CIVIL, URBAN AND TRANSPORTATION ENGINEERING 2020 12

INFLUENCE OF SURFACE MODIFICATION OF ARTIFICIAL WASTE ON STRENGTH OF CEMENTITIOUS COMPOSITE

Agnieszka KOCOT1, Tomasz PONIKIEWSKI1

1Department Civil Engineering, Civil Engineering, Silesian University of Technology, Ul. Akademicka 5a, Gliwice, Poland

[email protected], [email protected]

Abstract. High development of civilisation leads to incremental growth of produced municipal wastes. Despite of introducing restrictions related to municipal selective waste management still great amount of wastes is being landfilled. In countries like India or Philippines engineers started to utilize plastic wastes in extraordinary way using it as an alternative aggregate in cementitious composites. Many researchers tried to improve properties of concrete containing artificial aggregate. This paper analyses various treatment of PET flakes before adding to the mortar mix. The main aim was to modify the surface of PET flakes in order to obtain improved adhesion between artificial aggregate and cement matrix. Mortar mixes contained boiled, stored in alkali and acid solutions and regular plastic particles. This paper presents the results of flexural and compressive strength after 28 days and SEM analysis.

Keywords

Mortar, PET flake, plastic waste aggregate, surface modification.

1. Introduction

High rate of industrial development leads to incremental growth of consumed goods. Every year number of municipal wastes significantly increases. Poland belongs to the group of European countries with ban of landfilling high calorific wastes (over 6000 kJ/kg dry mass), however still over 40% of all the municipal wastes in Poland were disposed to landfills in 2018.

1.1. Waste management Figure 1 represents the plastic post-consumer waste rate management for selected European countries. According

to the data provided by Conversio Martket & Strategy GmbH [2], Poland in 2018 recycled 27% of collected plastic waste and over 42% was landfilled.

Fig. 1: Plastic post-consumer waste rate [2].

1.2. Artificial wastes in cementitious composites

Substitution of natural aggregate with plastic post-consumer waste is challenging, mainly due to decrease of mechanical properties of cementitious composites [4]. The reduction of strength may be caused by poor bond between cement matrix and plastic particles [3].

Researchers tried to modify the surface of PET particles by irradiating plastic by gamma ray. Compressive strength increased by about 25% in comparison to non-

treated particles, but still there was significant reduction of strength comparing to control cement paste [5].

Modification of PET surface was also provided by immersing particles in different solutions like water, bleach and alkaline bleach, nevertheless this approach

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also resulted in strength decrease in comparison to control concrete [1].

2. Materials and methods

Standard mortar with water/cement ratio equal 0,5 was the control sample. In this research 5% of volume of sand was replaced by the same amount of PET flakes. Plastic aggregate consisted of previously washed shredded PET bottles with dimension 0,5-4 mm.

Artificial aggregate was immersed in 3 different solutions namely boiling water, 5% NaOH and 5% HCl. The flakes remained in alkali and acid solutions for 2 and 24 hours and after washing and drying plastic waste substituted natural aggregate in mortar.

Figure 2 shows flat surface with scratches after the mechanical process of shredding PET bottles.

After immersing flakes in acid solution there was no additional matter, but the surface become more rough and more scratches became visible.

Fig. 2: Non-treated PET flake surface under Scanning Electron Microscope.

Although there is significant change in PET flakes surface comparing to non-treated particles, after applying the Energy Dispersive X-ray Spectroscopy (EDS) on plastic immersed previously in alkali solution (fig. 3) there was no change in chemical composition.

Fig. 3: PET after immersion in NaOH solution for 24 hours.

3. Results

Figure 4 represents the compressive strength of mortars after 28 days of curing. Substitution of 5% volume of sand with artificial wastes decreased the strength by 7%. Although the surface of plastic flakes was more rough after treating with different solutions it did not result in improvement of compressive strength.

After immersing PET flakes in boiling water or alkali solution for 2 hours the strength of mortar decreased by about 8% in comparison to non-treated particles.

The bar graph in figure 4 shows that treatment PET flakes with aggressive solutions, excluding particles immersed in HCl for 24 hours, decreased the compressive strength of mortars.

Fig. 4: Compressive strength of mortars after 28 days.

Figure 5 presents interfacial transition zone between cement matrix and plastic aggregate. In this picture visible gap with width about 4 μm is presumably caused by wall effect.

Fig. 5: Mortar containing 5% of non-treated PET flakes.

Figure 6 presents interfacial transition zone between cement matrix and PET particle treated with alkali solution for 24 hours. More extensive cracks are visible, moreover some particles of CSH attached to the surface of plastic aggregate were separated from cement matrix.

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Fig. 6: Mortar containing 5% of PET flakes immersed in NaOH for 24 hours.

4. Conclusion

Although the surface of PET flakes modified by alkali and acid solutions appeared to become more rough there was no improvement in compressive strength. Moreover after immersing plastic aggregate in boiling water, wherein the temperature exceeded glass transition temperature, strength decreased by 8,3% in comparison to non-treated PET mortar. This research shows that different approach of PET surface modification needs to be developed in order to classify PET flakes as a valuable replacement of natural aggregate.

Acknowledgements

The authors are thankful to Luleå University of Technology for enabling the access to Scanning Electron Microscope. The project is financed by the Polish National Agency for Academic Exchange no PPI/APM/2018/1/00004/U/001.

References

[1] NAIK, T. R. ; SINGH, S. S. ; HUBER, C. O. ; BRODERSEN, B. S.: Use of post-consumer waste plastics in cement-based composites. In: Cement and Concrete Research Bd. 26 (1996), Nr. 10, S. 1489–1492

[2] PLASTICSEUROPE: Plastics – the Facts 2019 (2019)

[3] RAHMANI, E. ; DEHESTANI, M. ; BEYGI, M. H A ; ALLAHYARI, H. ; NIKBIN, I. M.: On the mechanical properties of concrete containing waste PET particles. In: Construction and Building Materials Bd. 47, Elsevier Ltd (2013), S. 1302–1308

[4] SAIKIA, NABAJYOTI ; DE BRITO, JORGE: Use of plastic waste as aggregate in cement mortar and

concrete preparation: A review. In: Construction and Building Materials Bd. 34, Elsevier Ltd (2012), S. 385–401 — ISBN 0950-0618

[5] SCHAEFER, CAROLYN E. ; KUPWADE-PATIL, KUNAL ; ORTEGA, MICHAEL ; SORIANO, CARMEN ; BÜYÜKÖZTÜRK, ORAL ; WHITE, ANNE E. ; SHORT, MICHAEL P.: Irradiated recycled plastic as a concrete additive for improved chemo-

mechanical properties and lower carbon footprint. In: Waste Management Bd. 71, Elsevier Ltd (2018), S. 426–439 — ISBN 0141-3910

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THE 3RD INTERNATIONAL CONFERENCE

ON SUSTAINABLE DEVELOPMENT IN CIVIL, URBAN AND TRANSPORTATION ENGINEERING 2020 15

THE SUITABLE DISCRETIZATION OF CONCRETE PLATE FINITE

ELEMENT MODEL EXPOSED TO HIGH VELOCITY LOADING

Daniel JINDRA1, Petr HRADIL1, Jiří KALA1, Petr KRÁL1,2

1Institute of Structural Mechanics, Faculty of Civil Engineering, Brno University of Technology,

Veveří 331/95, 602 00 Brno, Czech Republic 2Faculty of Civil Engineering, VŠB – Technical University of Ostrava,

Ludvíka Podéště 1875/17, 708 00 Ostrava-Poruba, Czech Republic

[email protected], [email protected], [email protected], [email protected]

Abstract. Numerical approach using the FEM has been

used to model the behaviour of the reinforced concrete

specimen subjected to the pressure blast wave. The

concrete structure is a plate freely supported around the

perimeter by a steel plate and a concrete base. A

simplified 3D blast model has been used, which involves

the pure Lagrangian approach of FEM. The analyses

have been conducted using explicit solver. Non-linear

material model of concrete, continuous surface cap

model, has been used to capture the concrete behaviour.

Influences of various discretization features on the final

results (crack patterns, vertical deflection) are being

monitored, compared with physical experiment data and

discussed.

Keywords

Blast load, continuous surface cap material model,

discretization, explicit analysis, numerical nonlinear

analysis, reinforced concrete plate.

1. Introduction

Concrete is one of the most widely used materials in civil

engineering. Structures with high level of reliability are

required to withstand not only standard situation loads,

but also need to retain its resistance while exposed to

severe extreme loads, such as e.g. explosions [1] or

impacts [2]. In these cases, advanced modelling methods

and non-linear material models needs to be used, as e.g.

by Nueberger et al [3] or by Králik who modelled the Aircraft impact [4]. Behaviour of concrete is

mathematically described by many different material

models, each defined by various parameters. Different

approaches in modelling, material models, discretization

features and model settings are suitable for different

loading situations.

The objective of this paper is to investigate the

influence of various mesh sizes and mesh shapes of the

concrete plate discretization, and also in the contact area

between the concrete specimen and the supporting steel

plate.

Concrete structures exposed to blast loading have

been modelled e.g. by Tai et al [5]; Zhao and Chen [1]

[6]; Thiagarajan et al [7]; Dubec, Maňas, Štoller and Stonis [8]. In this study, closer focus on a mesh size and

shape influences is investigated.

1.1. Physical model

Fig. 1: Model geometry.

Fig. 2: Physical experiment set-up.

Physical experiments of the concrete plate specimen have

been conducted and documented. In the height of 10 cm

above the concrete plate centre, explosive of 75 g TNT

has been placed (see Fig. 1:). Two specimen of

considered explosive distance have been tested.

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The physical model geometry is depicted in the Fig.

1: Concrete plate is reinforced by a steel reinforcement

bars Ø 6 á 100 mm in both perpendicular directions

situated approximately in the middle of the plate height.

Fig. 3: Detail of the concrete plate specimen after the explosion.

1.2. Numerical model

A numerical finite element model of the structure has

been created. Explicit approach of solving the equation of

motion by a modification of the central difference time

integration implemented in this solver is suitable for

analysing structures exposed to impact loading.

Non-linear continuous surface cap concrete material

model (CSCM) [9] [10] has been used to model the plate

behavior. The parameters of this model are well

documented [11]. The uniaxial compressive strength of

30 MPa has been used. The CSCM is based on a yield

surface defined by the following function [12], [13]:

𝑌(𝐼1, 𝐽2, 𝐽3) = 𝐽2– 𝑅(𝐽3)2𝐹𝑓2(𝐼1)𝐹𝑐(𝐼1, 𝜅) (1)

where 𝐼1 is the first invariant of the stress tensor. 𝐽2 and 𝐽3

are invariants of the deviatoric stress tensor. 𝑅(𝐽3) is the

Rubin strength reduction factor and 𝜅 is the cap

hardening parameter. The yield surface consist of two

parts: the shear failure surface 𝐹𝑓(𝐼1); and the hardening

compaction surface 𝐹𝑐(𝐼1, 𝜅). The shear failure surface is

defined:

𝐹𝑓(𝐼1) = 𝛼– 𝜆 𝑒–𝛽 𝐼1 + 𝜃𝐼1 (2)

where material constants 𝛼, 𝛽, 𝜆 and 𝜃 are determined by

triaxial compression test results. The expression of the

hardening compaction surface is defined by equations:

𝐹𝑐(𝐼1, 𝜅) = 1– (𝐼1–𝐿(𝜅))2(𝑋(𝜅)–𝐿(𝜅))2 𝑓𝑜𝑟 𝐼1 > 𝐿(𝜅) (3)

𝐹𝑐(𝐼1, 𝜅) = 1 𝑓𝑜𝑟 𝐼1 ≤ 𝐿(𝜅) (4)

𝐿(𝜅)= 𝜅 𝑓𝑜𝑟 𝜅 > 𝜅0 (5)

𝐿(𝜅)= 𝜅0 𝑓𝑜𝑟 𝜅 ≤ 𝜅0 (6)

𝑋(𝜅) = 𝐿(𝜅) + 𝑅𝐹𝑓(𝐼1) (7)

where 𝑅 is the cap aspect ratio. Hardening compaction

surface and the shear failure surface are combined by a

multiplicative formulation which allows their continuous

and smooth combination at their intersections.

Both, reinforcement bars and support steel plate are

considered by isotropic material model with plastic

kinematic hardening. For these steel materials, elastic

Young’s modules of 200and 210 GPa respectively have

been used. Yield stresses of 500 and 235 MPa

respectively have been defined. The rubber material

between steel plate and concrete base is considered as

ideal elastic. Anchorage of the steel plate in the concrete

base is provided by 4 bolts.

Solid elements have been used for concrete base,

rubber and test concrete plate. Steel plate is modeled by

shell elements, bolts and reinforcement by beams.

Hexahedron solid elements with reduced integration

(1 point) have been used.

Symmetric contacts with segment based formulations

(pinball algorithms) have been involved. These contacts

have been defined in following areas, between:

• the concrete plate and the supporting steel plate

(solid vs. shell element),

• the steel plate and the rubber beneath it (shell vs.

solid element),

• the rubber and the concrete base beneath it (solid

vs. solid element).

1.3. Applied loads

The simplified blast model which involves the pure

Lagrangian approach of FEM has been used. The blast

wave is considered as a pressure load applied at the top

surface of the concrete plate. The time dependence of

pressure applied in a certain location (Eq. 8.) is based on

the empirical blast loading functions by Randers-Pehrson

and Bannister [14]. The blast loading equation:

𝑃(𝑡) = 𝑃𝑟(𝑡) 𝑐𝑜𝑠2 𝜃 + 𝑃𝑖(𝑡)(1 + 𝑐𝑜𝑠2 𝜃 – 2𝑐𝑜𝑠 𝜃) (8)

where 𝜃 is the angle of incidence, depicted in the Fig. 4:. 𝑃𝑟(𝑡) and 𝑃𝑖(𝑡) are reflected and incident pressures

(overpressure) respectively, both dependent on time 𝑡,

and both defined by Friedlander equation (Eq. 9.) [15]. In

case of 𝑃𝑖(𝑡), the function is stated as follows:

𝑃𝑖(𝑡) = 𝑃𝑖𝑛𝑐.𝑚𝑎𝑥 (1 − 𝑡𝑡+) ∙ 𝑒–𝑎 𝑡𝑡+ (9)

where 𝑃𝑖𝑛𝑐.𝑚𝑎𝑥 is the peak incident pressure, 𝑎 is the

waveform number and 𝑡+ is the positive phase duration.

Parameters are defined in dependence on distance from

the centre of the blast 𝑅, and equivalent TNT mass 𝑊, in

a different way for 𝑃𝑖(𝑡) and 𝑃𝑟(𝑡).

No damping has been involved.

Fig. 4: Example of a blast wave pressure load.

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2. Results

The explicit analyses have been conducted for 4 different

mesh sizes of the concrete plate: 10 mm, 7.5 mm, 5 mm

and 2.5 mm. Applied loads have been the same in all

cases, as described in the previous chapter.

Blast wave reaches the structure approx. at 20 μs.

The differences of crack patterns are depicted in Fig.

6: by 1st principal strains at the bottom concrete plate

surface.

Deflection of the concrete plate is being observed in

the top-most element of the concrete plate in the mid-

span. This is because the higher plastic strains are

allocated in elements at the bottom surface of the slab,

therefore this might lead towards unreal values.

Fig. 5: Dependence of mid-span concrete plate vertical deflection

[mm] on time [μs].

Fig. 6: Depiction of 1st principal log strains for various meshes.

3. Discussion

In case coarser mesh (10 mm) of the solid elements has

been used to run the FEM explicit analysis, major crack

pattern direction is diagonal (Fig. 6: left). Finer mesh

(2.5 mm) leads towards cracks also in directions

perpendicular to concrete plate circumference. This

seems to be in much better match with the experimental

test data (Fig. 7:), where cracks have occurred mostly in

there perpendicular directions.

Maximal measured vertical deflections of the test

specimens were −3 mm and −3.5 mm. The values of

deflection obtained from the numerical analyses (Fig. 5:)

seems to be reasonable, just slightly lower. This could be

however also a reason of slightly different stiffness of the

whole model (steel plate, rubber, concrete base), which

has not been properly documented, and few estimated

parameters have been used to conduct the analyses.

In general, nice match between the numerical model

and the experimental data has been achieved.

Fig. 7: Crack patterns of the concrete plate after experimental tests.

4. Conclusion

In order to obtain better match between the crack patterns

of the real experimental data (Fig. 7:) and the numerical

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model (Fig. 6:), it is necessary to use very fine mesh of

the test specimen. Suitable size seems to be between

2.5 mm and 5 mm.

Mid-span deflection of the concrete plate is in a

sufficiently good match with numerical analyses data.

Acknowledgements

This paper has been created with the financial support of

the following projects: GAČR 17-23578S "Damage

assessment identification for reinforced concrete

subjected to extreme loading" provided by the Czech

Science Foundation; FAST-J-20-6256 provided by the

Brno University of Technology fund for the specific

university research.

References

[1] ZHAO, C.F., J.Y. CHEN, Y. WANG and S.J. LU.

Damage mechanism and response of reinforced

concrete containment structure under internal blast

loading. Theoretical and Applied Fracture

Mechanics. 2012, vol. 61, p. 12-20. ISSN 0167-

8442. DOI: 10.1016/j.tafmec.2012.08.002.

[2] FUJIKAKE, Kazunori, Bing LI a Sam SOEUN.

Impact Response of Reinforced Concrete Beam and

Its Analytical Evaluation. In: Journal of Structural

Engineering. ASCE, 2009, 135(8), p. 938-950.

ISSN: 0733-9445. DOI: 10.1061/(ASCE)ST.1943-

541X.0000039.

[3] NEUBERGER, A., S. PELES and D. RITTEL.

Scaling the response of circular plates subjected to

large and close-range spherical explosions. Part I:

Air-blast loading. International Journal of Impact

Engineering. 2007, vol. 34, iss. 5, p. 859-873. ISSN

0734-743X. DOI: 10.1016/j.ijimpeng.2006.04.001.

[4] KRÁLIK, J., Safety of nuclear power plant against

the aircraft attack. Applied Mechanics and

Materials. 2014, vol. 617, p. 76-80.

ISSN: 1662−7482. DOI:

10.4028/www.scientific.net/AMM.617.76.

[5] TAI, Y.S., T.L. CHU, H.T. HU and J.Y.

WU.Dynamic response of a reinforced concrete slab

subjected to air blast load. Theoretical and Applied

Fracture Mechanics. 2011, vol. 56, issue. 3,

pages.140–147. ISSN 0167-8442. DOI:

10.1016/j.tafmec.2011.11.002.

[6] ZHAO, C.F. and J.Y. CHEN. Damage mechanism

and mode of square reinforced slab subjected to

blast loading. Theoretical and Applied Fracture

Mechanics. 2013, vol. 63-64, p. 54-62. ISSN 0167-

8442. DOI: 10.1016/j.tafmec.2013.03.006.

[7] THIAGARAJAN, G., A.V. KADAMBI, S.

ROBERT and C.F. JOHNSON. Experimental and

finite element analysis of doubly reinforced concrete

slabs subjected to blast loads. International Journal

of Impact Engineering. 2015, vol. 75, p. 162-173.

ISSN 0734-743X. DOI:

10.1016/j.ijimpeng.2014.07.018.

[8] DUBEC, B., P. MAŇAS, J. ŠTOLLER and P. STONIS. 2019. Experimental and numerical

assessment of fibre reinforced concrete slab under

blast load, ICMT 2019 - 7th International

Conference on Military Technologies, Proceedings

2019. ISBN: 978-172814593-8.

DOI: 10.1109/MILTECHS.2019.8870129.

[9] MURRAY, Y. D., User’s manual for LS-DYNA

concrete material model 159, Report No. FHWA-

HRT-05-063 Federal Highway Administration,

2007.

[10] MURRAY, Y. D., A. ABU-ODEH, R. BLIGH,

Evaluation of concrete material model 159, Report

No. FHWA-HRT-05-063, 2006.

[11] KRÁL, P., M. HUŠEK, P. HRADIL, J. KALA and P. MAŇAS, Optimization of the material parameters of the continuous surface cap model for concrete,

2017 International Conference on Military

Technologies (ICMT), Brno, 2017, pp. 298–302.

ISBN 978-1-5090-5666-8. DOI:10.1109/MILTECHS.2017.7988773.

[12] SCHWER, L. E., Y. D. MURRAY. A three invariant

smooth cap model with mixed hardening.

International Journal for Numerical and Analytical

Methods in Geomechanics, vol. 18, pp. 657-688,

1994. DOI: 10.1002/nag.1610181002.

[13] SANDLER, I. S., F. L. DIMAGGIO, G.Y. BALADI.

Generalized cap model for geological materials,

ASCE Journal of the Geotechnical Division,

vol. 102, pp. 683-699, 1976.

[14] RANDERS-PEHRSON, G. and K. A.

BANNISTER. Airblast loading model for DYNA2D

and DYNA3D. Army Research Laboratory, Rept.

ARL-TR-1310, US, 1997.

[15] FRIEDLANDER, F. G. The diffraction of sound

pulses I. Diffraction by a semi-infinite plane.

Proceedings of the Royal Society A. 1946. ISSN

0080-5630. DOI: 10.1098/rspa.1946.0046.

https://doi.org/10.1002/nag.1610181002

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AERODYNAMIC CHARACTERISTICS OF THE CYLINDER IN SUBCRITICAL AND CRITICAL REGIME

Ivan KOLOŠ1, Vladimíra MICHALCOVÁ 1 and Lenka LAUSOVÁ1

1Department of Structural Mechanics, Faculty of Civil Engineering, VSB – Technical University of Ostrava, Ludvíka Podéště 1875/17, Ostrava-Poruba, Czech Republic

[email protected], vladimira.michalcova @vsb.cz, [email protected],

Abstract. Flow around a cylindrical object is one of the frequently solved problems in many engineering disciplines. Despite the simple geometry of the cylinder, it is an interesting physical phenomenon. Partial knowledge of flow field properties can be found in literature, but in terms of their use for practical tasks, the data is still incomplete. The authors performed a numerical analysis of the flow around the smooth cylinder in the subcritical and critical region for Reynolds numbers in the range of Re = 2.3·103 to 2·105. Turbulent flow was solved using LES model. The calculations were compared with the available experimental data. Analysis of the mean stream velocity showed that the range of negative values in the wake decreases with increasing Re up to 1.4·105. The area in the immediate vicinity behind the cylinder remains unclear, as all numerical simulations show positive velocity values, while according to experiments the velocity is negative. The pressure coefficient evaluation showed a big difference between its distribution in the subcritical and critical region. In the subcritical region, a relatively good agreement between calculation and experiments was achieved, but in the critical region, good agreement is achieved on the leeward side only. In contrast, the results of Strouhal number well matched the assumptions and, in accordance with the experiments, grow in the critical region with increasing Re. The results of the drag coefficient confirm its decreasing trend in the transition from subcritical and critical regions, which is indicated in experiments.

Keywords

CFD, LES, subcritical and critical regime, cylinder, flow characteristics.

1. Introduction

One of the long-term topics in engineering practice is the effect of wind or water on cylindrical cross-section structures. It concerns various types of structures such as

cooling towers, chimneys, tall buildings (e.g. Fig. 1), columns, bridge structures, offshore structures, air-cooled heat exchanges, storage tanks and other industrial buildings and their structural components.

From the point of view of fluid mechanics, it is a topic of flow around a circular cylinder, which is a relatively complex phenomenon, which depends on many parameters. The physical complexity of the flow around the cylinder and the sensitivity of the flow field to the small variations of the quantities that affect them have been motivating many research teams for experimental and numerical research for many years, for both theoretical and practical reasons.

Fig. 1: Buildings of cylindrical cross-section https://konstrukce.cz/architektura-a-development/ekologicka-budova-v-centru-prahy-green-point-170, https://www.vodarenskeveze.cz/Bohumin_Novy_Bohumin/Bohumin_Novy_Bohumin.html

With turbulent wind flow around building structures, the Reynolds number Re often ranges from 1·105 to 1·107. This is the zone of transition between the so-called subcritical and critical region. Available measurements show that this transition zone between subcritical and critical regimes shows significant changes in flow properties. There are not many experimental data for this zone because it is not easy to perform measurements for Re over the whole range, especially at low or very high flow rates. Although partial results of experiments for some of the Re values for subcritical and critical regions can be found in the scientific literature, they do not give a sufficiently detailed picture of the flow field properties in terms of practical tasks, especially in civil engineering and wind engineering.


mailto:vladimira.michalcova%[email protected]


https://konstrukce.cz/architektura-a-development/ekologicka-budova-v-centru-prahy-green-point-170

https://konstrukce.cz/architektura-a-development/ekologicka-budova-v-centru-prahy-green-point-170

https://www.vodarenskeveze.cz/Bohumin_Novy_Bohumin/Bohumin_Novy_Bohumin.html

https://www.vodarenskeveze.cz/Bohumin_Novy_Bohumin/Bohumin_Novy_Bohumin.html

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The numerical study in this article tries to contribute to the addition of information about velocity field properties, while calculations are verified on the basis of available experimental data. The aim was to describe the properties of the velocity field in subcritical and critical regimes and to find the optimal variant of the numerical solution. Due to the use of results in various areas of engineering practice (i.e. flow at higher and lower Re), the authors decided to use the obtained experimental data in the interval Re = 2.3·103 to 2·105.

The problem is solved by finite volume method in commercial software Ansys Fluent which allows good parallelization of the computational domain. The calculations are performed for 6 specific Re. High performance computer was used in the calculation, as it is necessary to use an advanced turbulent model and an appropriately fine mesh to perform the calculation. The following characteristics are monitored: velocity profile in the wake behind the cylinder, pressure load distribution on the cylinder (pressure coefficient cp), see Fig. 2, the resistance force of an object (drag coefficient cd), frequency of vortex shedding (lift coefficient cl), Strouhal number St.

Fig. 2: Mean pressure distribution, critical regime, CFD and experimental data

2. Task Description

Isothermal flow around a smooth cylinder with the nature of the flow for six different Re numbers, Re(2.3·103 2·105), is modeled. In all cases the cylinder diameter is identical, the Reynolds number change is ensured by the change in velocity of the flow.

Re = 4·103 Re = 1.4·105

Fig. 3: RMS of mean stream velocity fluctuations

The task is solved numerically using the LES turbulence model (Large eddy simulation). Comparison of mean stream velocity fluctuations in the flow field for values Re = 4·103 and 1.4·105 is shown in Fig. 3.

3. Conclusion

For the velocity field, the so-called core of the wake was evaluated, i.e. the area with a negative value of mean stream velocity. CFD simulations showed shortening of the core of the wake with increasing Re number up to its value Re = 1.4·105. At higher Re, the core of the wake was no longer shortened in numerical simulations. The area in the immediate vicinity of the cylinder remains unclear, since according to experiments the mean stream velocity is negative while all numerical simulations show positive ux values.

When investigating the cylinder pressure load in the subcritical region, a relatively good agreement was achieved between numerical calculation and physical experiments. For the distribution of the pressure coefficient cp in the critical region, good agreement is only achieved in the leeward area. In terms of evaluation of extreme pressure load (cp,min), CFD calculations show higher values than experiments in this critical region. This confirms the complexity of the issue, which is also reflected in the ambiguity of the experimental results of the various research teams. Given the importance of cp, especially in civil engineering (i.e. the distribution of loads from the effects of wind on the perimeter of the structure), it is necessary to devote greater effort to this topic in both numerical modeling and experimental research.

The results of St correspond to the assumptions and in accordance with the experiments grow in the critical region with increasing Re.

The results of the drag coefficient cd confirm the decreasing trend of cd values in the transition from the subcritical and critical regions and partly complement the missing data for the vicinity close to Re = 1.5·105. The drag coefficient at this high Re is also of great importance in civil engineering, since it defines the degree of load of the circular cross-section structure from the effects of wind.

Acknowledgements

The paper has been supported by the project of

“Conceptual development of science and research activities 2020” on the Faculty of Civil Engineering, VŠB – TU Ostrava and by the Ministry of Education,

Youth and Sports from the Large Infrastructures for

Research, Experimental Development and Innovations

project „IT4Innovations National Supercomputing Center.

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NUMERICAL MODEL OF TENSILE TEST OF STEEL S390D USED IN THIN-WALLED STRUCTURES

Jakub FLODR1, Petr LEHNER1, Martin KREJSA1

1Department of Structural Mechanics, Faculty of Civil Engineering, VSB – Technical University of Ostrava, Ludvíka Podéště 1875/17, Ostrava-Poruba, Czech Republic

[email protected], [email protected], [email protected]

Abstract. The article presents a comparison of the results of a physical experiment and a numerical model of the tensile test. This evaluation serves for the development of the numerical model of the clinch connection. The numerical model of the clinch connection will be developed based on the real geometry of the samples. ANSYS software was used for the static analysis of the stress test. Results from numerical model can serve to verification of all types of joints.

Keywords

Numerical modelling, Tensile, Experiment.

1. Introduction

Many civil engineering buildings consist of thin-walled beams and shells. These structures can be built using clinching technology. Joining materials is a method of joining materials without additional binders using tools that permanently join materials and create a mechanical point without any fastener [1, 2]. The shape of the hinge depends mostly on the chosen combination of dies and dies - it can be round or square, with or without notches of the connected sheets [3, 4]. Securing is offered as an interesting alternative for connecting thin-walled sections in the construction industry. Thin-walled profiles are widely used mainly for cost reduction purposes, to reduce the weight of a structure and it’s potential for automating production [5–7]. Creating double sections is a very convenient way where two sections are connected, eg columns, trusses and other structural components to increase the load-bearing capacity and overall rigidity of the structural system. Suitable sections are, for example, the Omega, C and U profiles. There is currently no methodology available to deal with a proposal to evaluate such interconnection according to the legislation in force. In practice, these sections are often joined together using

standard screws to form a grid. However, such construction has problems with its efficiency and economy [8, 9]. Previous research of the authors’ team was concerned with an analysis of available options for clinching and their suitability for use in civil engineering. After selecting an adequate solution, the research focused on the clinching process and analysed in [10] using LS-DYNA software [11] in order to understand it better. As a result, it was necessary to find another solution based on the new numerical model prepared in ANSYS software [12].

2. Material Parameters Test

The tensile test of the steel sheet without join was prepared. Tested samples were made from the material S390GD with guaranteed yield point 390 MPa. The thickness of the basic material is 2.67 mm. The finite-element model was prepared in ANSYS system. The model was created in true-to-scale to the physical experiment, so that maximum compliance was reached. The physical experiment was conceived as a tensile test and completed by its destruction (see Fig. 1).

Fig. 1: Comparing the result of the material property test and the numerical model simulation.




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Testing was made on standard bodies designed for the tensile tests. To define the actual material model, the tensile test was subsequently modelled in ANSYS system, where the actual material model was determined using an iteration method (see Fig 2.).

Fig. 2: Multilinear isotropic material model in ANSYS Software.

3. Conclusion

The model prepared in the ANSYS software is based on isoparametric finite elements and their dimensions are same as the sample size. In Figure 1, we can see the sample after rupture, and the corresponding numerical model in ANSYS. It can be seen from this figure that the slope of the failure on the tested sample corresponds to the stress of the model. The deformation of the finite element network is very similar to that of actual deformation of the ruptured sample. As mentioned before, it is a S390GD material with a guaranteed yield strength of 390 MPa and a strength limit of approx. 460 MPa. On the colour scale in Figure 2, it can be observed that values at rupture place are relatively close to the expected results. To define the real material model, tensile test subsequently modelled in ANSYS software. This will be served for prepared evaluation and modelling of the clinch connections.

Acknowledgements

This article has been completed thanks to the financial support provided to VSB-Technical University of Ostrava by the Czech Ministry of Education, Youth and Sports from the budget for conceptual development of science, re-search and innovations for the year 2020.

References

[1] TOMÀ, A., G. SEDLACEK and K. WEYNAND. Connections in cold-formed steel. Thin-Walled Structures. 1993, vol. 16, pp. 219–237. ISSN 02638231. DOI: 10.1016/0263-8231(93)90046-D

[2] HAMEL, V., J. M. ROELANDT, J. N. GACEL and F. SCHMIT. Finite element modeling of clinch

forming with automatic remeshing. Computers and Structures . 2000, vol. 77, iss. 2, 185–200. ISSN 00457949. DOI: 10.1016/S0045-7949(99)00207-2

[3] PEDRESCHI, R. and B. SINHA. Predicting the Shear Strength of Mechanical Clinching in Cold-Formed Steel Structures. Journal of Materials in Civil Engineering. 2006, vol. 18, , iss. 6, pp. 435–442. ISSN 0899-1561. DOI: 10.1061/(ASCE)0899-1561(2006)18:3(435)

[4] LAMBIASE, F. and A. DI ILIO. An experimental study on clinched joints realized with different dies. Thin-Walled Structures. 2014, vol. 85, pp. 71-80. ISSN 02638231. DOI: 10.1016/j.tws.2014.08.004

[5] CHEN, C., S. ZHAO, X. HAN, M. CUI and S. FAN. Investigation of mechanical behavior of the reshaped joints realized with different reshaping forces. Thin-Walled Structures. 2016, vol. 107, pp. 266–273. ISSN 02638231. DOI: 10.1016/j.tws.2016.06.020

[6] ANBARASU, M., S. B. KUMAR and S. SUKUMAR. Study on the effect of ties in the intermediate length Cold Formed Steel (CFS) columns. Structural Engineering and Mechanics . 2013, vol. 46, iss. 3, pp. 323–335. ISSN 12254568. DOI: 10.12989/sem.2013.46.3.323

[7] BARTCZAK, B., D. GIERCZYSK-ZBROZEK, Z. GRONOSTAJSKI, S. POLAK and A. TOBOTA. The use of thin-walled sections for energy absorbing components: and review. Archives of Civil and Mechanical Engineering . 2010, 10, iss. 4, pp. 5–19. ISSN 1644-9665. DOI: 10.1016/S1644-9665(12)60027-2

[8] PRAMANIK, A., A.K. BASAK, Y. DONG, P.K. SARKER, M.S. UDDIN, G. LITTLEFAIR, A.R. DIXIT and S. CHATTOPADHYAYA. Joining of carbon fibre reinforced polymer (CFRP) composites and aluminium alloys – A review. Composites Part A: Applied Science and Manufacturing . 2017, vol. 101, pp. 1–29. ISSN 1359-835X. DOI: 10.1016/J.COMPOSITESA.2017.06.007

[9] LÜDER, S., S. HÄRTEL, C. BINOTSCH and B. AWISZUS. Influence of the moisture content on flat-clinch connection of wood materials and aluminium. Journal of Materials Processing Technology . 2014, vol. 214, iss. 10, pp. 2069–2074. ISSN 0924-0136. DOI: 10.1016/J.JMATPROTEC.2014.01.010

[10] FLODR, J., P. KAŁDUŃSKI, M. KREJSA and P. PAŘENICA. Innovative Connection of Steel Profiles, Experimental Verification and Application. Procedia Engineering . 2017, vol. 190, pp. 215–222. ISSN 18777058. DOI: 10.1016/j.proeng.2017.05.329

[11] HALLQUIST, J. LS-DYNA® theory manual. In: LS-DYNA Theory Manual . 2006. ISBN 9254492507. DOI: 10.1126/science.281.5381.1363

[12] ANSYS. ANSYS Meshing User’s Guide. ANSYS User Guide. 2016, 15317 (January), 514.

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3D NUMERICAL CALCULATION OF STRESS INTENSITY FACTOR ON I-PROFILE BEAM UNDER THE BENDING LOAD

Jorge ÁLVAREZ MORÁN1, Stanislav SEITL2,3, Petr MIARKA2,3

1University of Oviedo, San Francisco, 3, 33003 Oviedo, Spain. 2 Institute of Physics of materials, Czech Academy of Sciences Žižkova 513/22 616 62, Brno, Czech Republic

3Institute of Structural Mechanics, Faculty of Civil Engineering Brno University of Technology; Veveří 331/95, 602 00 Brno, Czech Republic

[email protected], [email protected], [email protected],

Abstract. Steel structures used in civil engineering industry have components which can contain cracks. In most of the cases, these components are beams with an I-profile cross-section. Therefore, it is of major interest to set the remaining service-life time of a such damaged structure. That is why a numerical model of an I-profile was made to calculate the stress intensity factor and to analyse the stress distribution in a region near to the crack.

Keywords

Stress Intensity Factor, Linear Elastic Mechanics, I-Profile, Finite Element Method.

1. Introduction

Many structural components in civil structures, such as bridges or buildings [1][2], are built from I profiles [3]. The aim of these profiles is to reduce the material, which leads to cost reduction of whole structure and its weight. Nevertheless, such a structural element has the same load bearing capacity, when subjected to bending loads, as it would have with rectangular cross-section. When is the structural element subjected to the bending load, high stress concentrations are mainly located at the upper and lower parts of the cross section, see Figure 1. In this study the three-point bending (3PB) test was analysed in finite element method (FEM) software with an I-profile cross-section.

Structural elements can contain defects and imperfections, such as cracks. These cracks usually propagate during the service life of the structural element. Thus, it is of major interest to have a proper description of crack propagation.

Moreover, a linear elastic fracture mechanics (LEFM) [4] suggest such an application with the stress intensity factor used as a main describing quantity of stress field [5], [6] in the vicinity of the crack tip.

Fig. 1: Sketch of 3PBT for two different cross sections: rectangular and I-profile for the same width, W and normal stress.

The objective of this article is to describe and compare the stress intensity factor near a short edge crack of a rectangular specimen with a selected I-profile. Moreover, the study was performed for different crack lengths materials and web thicknesses; but with a constant flange thickness. See Figure 2.

Fig. 2: Sketch of a typical dimensions of studied I Profile.




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2. Theoretical Background

As explained before, the LEFM is used as the main theory for crack propagation. It is based on the Paris-Erdogan’s law [7] and tested by standard[8]. The following equation is used to describe the SIF for an angle = 0°

𝐾I = 𝜎𝑦𝑦 √2𝜋𝑟 (1) where KI is the stress intensity factor for mode I, where σyy is the applied stress and r is the distance from the crack tip.

3. Numerical Modelling

The selected I profile was modelled with a 3D FEM software ANSYS. The numerical model with a symmetry and boundary conditions is shown in Figure 3. Material properties were a Young’s modulus and a Poisson’s ratio which were varying based on studied material i.e. steel, concrete, aluminium, clay. Symmetry conditions were applied in the model, which allows to model only half of the specimen and resulted into reduction of the computational time.

Fig. 3: Example of mesh with applied boundary conditions prepared in

ANSYS

From a numerically generated stress factor for varying material and model geometry a stress intensity was calculated by using Eq. 1.

Acknowledgements

The financial support of the grant No. 20-00761S is

greatly appreciated.

References

[1] KALA, Z. Global sensitivity analysis of reliability of structural bridge system. Engineering Structures. 2019, vol. 194, pp. 36-45. DOI:

10.1016/j.engstruct.2019.05.045

[2] KALA, Z. Estimating probability of fatigue failure of steel structures. Acta et Commentationes Universitatis Tartuensis de Mathematica,. 2019 vol. 23. Iss. 2, pp. 245-254. DOI: 10.12697/ACUTM.2019.23.21

[3] IPE Beams. EUROPEAN STANDARD UNIVERSAL I BEAMS (I SECTION) WITH PARALLEL FLANGES. DIMENSIONS, SPECIFICATIONS, ACCORDANCE WITH FORMER STANDARD EU. 2009 pp. 19-57

[4] IRWIN, G.R. Analysis of Stresses and Strains Near the End of a Crack Traversing a Plate, Journal of Applied Mechanics. 1957. Vol. 24, pp. 361-364.

[5] SEITL. S., MIARKA, P., KALA, Z. Geometry functions for edge cracks in steel bridge under three- and four- point bending with various span, Transactions of VSB-Technical University of Ostrava, Civil engineering series. 2018, vol. 18, iss. 2, pp. 44-49.

[6] TADA, H., PARIS, P.C. and IRWIN, G.R. (2000) The stress analysis of Cracks Handbook, New York

[7] PARIS, P.C. and ERDOGAN, F. A Critical Analysis of Crack Propagation Laws, Journal Basic Engineering. 1963, vol. 85, iss. 4, pp. 528-533

[8] ASTM E647-15. (2015) Standard Test Method for Measurement of Fatigue Crack Growth Rates. West Conshohocken, PA: American Society for Testing and Materials.

CUTE 2020 PAPER: 06


PROBABILISTIC ASSESSMENT TO DETERMINE SEISMIC LOAD CONSIDERING THE LOCAL SITE EFFECTS

Juraj KRÁLIK1, Juraj KRÁLIK, jr.2

1Faculty of Civil Engineering, STU Bratislava, Radlinského 11, 810 05 Bratislava, SK 2Academy of Fine Arts and Design in Bratislava, Hviezdoslavovo nám. 18, 814 37 Bratislava, SK


Abstract. The paper presents the results of problems of the soil-structure interaction considering the local site effects. The influences of the local site effects can significantly modify the stresses and deflections of the structural system. Two important characteristics that distinguish the dynamic soil-structure interaction system from other general dynamic structural systems are the unbounded nature and the nonlinearity of the soil medium. Generally, when establishing numerical dynamic soil-structure interaction models, the following problems should be considered.

Keywords

Seismic, Safety, SSI, Nuclear Power Plants, ANSYS.

1. Introduction

After the accident of nuclear power plant (NPP) in Fukushima the IAEA in Vienna adopted a large-scale project "Stress Tests of NPP", which defines new requirements for the verification of the safety and reliability of NPP. Based on the recommendations of the ASCE standard and IAEA in Vienna [1- 5], the effective seismic resistance of objects is assessed in PGA sites up to 0.3g according to the "Seismic Margin Assessment" methodology (SMA) [1]. The required methodology was based on a reference earthquake (RLE) or a "Seismic Mar-gin Earthquake" (SME) earthquake, which is an earthqua-ke with seismological parameters of a given site and response spectrum at the free terrain level corresponding to 84.1% probability. The Peak Ground Acceleration (PGA) is defined for a probability of no-exceedance in 104 years. The design response spectra were prepared based on results of the PSHA (Probabilistic Seismic Hazard Analysis) study for the NPP J. Bohunice site developed by GFÚ SAV [3]. The value of the PGA for horizontal and vertical excitation for the annual occurrence probability

(typically 10-4/year) is following

- horizontal acceleration peak - PGAH.RLE = 0.367g

- vertical acceleration peak - PGAV.RLE = 0.229g

Fig. 1: The cross section of the SVP SO841.

2. Response Spectrum Compatible Accelerograms

To provide input excitations to structural models for sites with no strong ground motion data, it is necessary to generate artificial accelerograms. It has long been established that due to parameters such as geological conditions of the site, distance from the source, fault mechanism, etc. different earthquake records show different characteristics. Thus, the simulated earthquake records must have realistic duration, frequency content, and intensity, representing the physical conditions of the site. Due to the complex nature of the formation of seismic waves and their travel path before reaching the recording



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station, a stochastic approach may be most suitable for generating artificial accelerograms. Earlier, stationary white noise random models for modeling earthquake ground motions were developed [3, 4].

Based on Kanai's investigation regarding the frequency content of different earthquake records, Tajimi proposed the following relation for the spectral density function of the strong ground motion with a distinct dominant frequency:

( )( )

( ) ( )

22

02 22

1 4

1 4

+ = − +

g g

g g g

S S (1)

Here g and g are the site dominant damping coefficient and frequency, and S0 is the constant power spectral intensity of the bed rock excitation. The Kanai-Tajimi power spectral density function may be interpreted as corresponding to an "ideal white noise" excitation at the bedrock level filtered through the over-laying soil deposit at site. The generalized nonstationary Kanai-Tajimi model is represented by the following equations:

22 ( ) + + =f g g f g f

u u u y t ,

2(2 ). ( ) = − +

g g g f g fu u u e t , (2)

where f

u is the filtered response, g is dominant ground

frequency, g

u is the output ground damping acceleration,

and e(t) is the amplitude envelope function. After

numerical integration of equations (2) can be evaluated the

ground damping acceleration g

u .

To generate a synthetic ground motion accelerogram a(t) compatible with a response spectrum, the following steps can be used according to [3]:

1. A simple time function y(t) can be established from natural accelerograms or as gaussian distribution with zero mean value and a variance of unity. The function y(t) is a stationary Gaussian white noise process -

E[y(t)] = 0, E[y(t1), y(t2)] = 2S0(t1-t2) (3)

2. A nonstationary function z(t) can be obtained from the stationary-type waveform y(t) and the deterministic time function f(t) as follows

( ) ( ) ( ).=z t y t f t , ( )( )

( )2

2

1 1

1 2

2

1

− −

=

c t t

t t t t

f t t t t

e t t

, (4)

where the values t1, t2 and c depends on earthquake magnitude and epicentral distance.

3. Using Fast Fourier Transformation (FFT) we can get Z(i) from the wave form z(t) and the complex function A(i) after the filtration of the smaller frequency than 2 and lower frequency than 1

( ) ( ). .

−

−

= i tZ i z t e dt , ( ) ( ) ( ). =A i Z i H i (5)

where the function H(i) is modified Kanai-Tajimi filter function in the form

( )1

1

2 22

1 22 2

1 21 2

1 2

.

1 2. . . . 1 2. . .

+

=

− + − +

i

H i

i i

, (6)

4. The normalized accelerogram a(t) will be got from the complex function A(i) in (5) after the inverse FFT transformation

( ) ( )1.

−

= i t

n

peak

a t A i e da

, (7)

5. The accelerogram spectrum ( ),a

pv sS T can be

considered as maximum acceleration response of a single degree-of-freedom (SDOF) structure under the ground acceleration

22 + + = −

s s s gu u u u , (8)

where s and s are the fundamental frequency and the damping coefficient of the SDOF. The accelerogram spectrum is defined as ( ) , max ( ) =a

pv sS T u t .

6. The accelerogram spectrum ( ),a

pv sS T must be

compared with design spectrum ( ),pv s

S T . The correla-tion function can be obtained for frequency band or for the value of discrete frequency using in FFT method. We can describe the difference area of the accelerogram spectral function and the design spectral function for interval <T1, T2>

2

1

( ( , ) ( , )). = −T

a

pv s pv s

T

J S T S T dT ,

2

1

( , ).= T

pv s

T

J S T dT (9)

If / J J toler (where “toler” is a permissible deviation), we must start the correction process. This iteration will be finished for condition / J J toler . The average of the ratios of design spectral value ( ),

pv sS T to

response spectral value ( ),a

pv sS T over each frequency

band were used to multiply the real and imaginary parts of A(i). After this reduction are calculated next steps to get the new modified accelerogram.

Presented iteration process is not explicit converged. This iteration process requires the control system of the convergence. We can use the implicit method (using three last correction parameters for each frequency band) to consider optimal parameter for next step. If the solution is diverged, we can take a step back with correction of this parameter. The FORTRAN program "COMPACEL" has been created by author to generate synthetic ground motion accelerograms assuming the site effect and requirement of standard (Eurocode 8 (Europe), AFPS 90

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0

0,2

0,4

0,6

0,8

1

0,0001 0,001 0,01 0,1 1 10

G/G

max

Shear strain [%]

Clay

Sand

Rock

(France), ASCE 4-86 (USA), NUREG /CR-0098 (USA), DIN 49 (Germany), JSCE 92 (Japan), STN 730036 (Slovak) and the minimal square deviation method was applied.

The horizontal and vertical response spectrum RLE are shown in the graphs (see Fig.2). These spectra were used as inputs for generating synthetic three-component accelerograms. The values of seismic motion (see Fig.3) for the nuclear fuel storage SVP are taken from the report of the Geophysical institute [3].

Fig. 2: The response spectrum from the synthetic accelerograms in direction X, Y and Z for 5% damping.

Fig. 3: The spectrum compatible synthetic accelerogram.

3. Geophysical subsoil properties of the locality

For seismic analyses, it was recommended to use the seismic assignment for the nuclear fuel storage SVP at J. Bohunice site according to data in the feasibility study. Tab. 1: Geological profile under the building SVP SO841.

[t/m3]

Gdyn [Mpa]

Mean Median NEP 84%

2,00 20,00 20,00 20,00

2,00 107,66 112,67 121,70

2,20 323,30 372,75 404,70

2,00 441,80 441,80 445,57

2,15 524,47 537,50 542,59

2,20 929,50 929,50 929,50

2,20 1627,12 1627,12 1627,12

Dynamic soil characteristics were obtained with sufficient accuracy from the refractive and reflexive survey of a given site [3]. Depending on the propagation rates of the longitudinal and transverse waves in the soil, we can determine its physical characteristics.

The basic rigid parameter characterizing the earth body for dynamic calculations is the dynamic Gdyn

Gdyn = vs2, ( ) ( )2 2 2 2

dyn p s p s2 / 2v v v v v = − − (10)

where is the soil density, vs - the velocity of the shear waves propagation in the respective earth (layer), vp is the velocity of the longitudinal waves.

4. Stiffness and damping soil parameters in the subsoil

In the case of earthquakes, there is a large movement of the soil, and because of plastic deformation, the value of the dynamic soil module also drops [5-7]. According to IAEA recommendations, this reduction will maximally reach 65% of the dynamic module measured for small seismic events. The process of the shear modulus and the damping can be seen in Fig. 4 depending on the shear strain [3].

Fig. 4: Shear modulus dependence on the shear strain.

5. Seismic hazard considering site effects

The methodology for analyzing the influence of the layered subsoil of type 3 (for vs < 300 m/s) according to the requirements of the IAEA NS-G-3.6 was used to define the seismic load for the nuclear fuel storage. The seismic load RLE was defined assuming that seismic waves are transformed from the source to the site in a rock bed (for vs > 1100m/s).

Local design acceleration spectra were calculated considering the SSI effects used the SHAKESI program in accordance with the recommendations of the standards IAEA [2] and U.S. NRC.

Therefore, the methodology for calculating local design spectra is based on the following assumptions: • PGA values for RLE seismicity were determined for

the free field assuming the rigidity of the bed of the corresponding to the rock subsoil (for vs > 1100m/s)

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• The response spectrum acceleration for SL-2 [3] were defined based on a probabilistic analysis of the site effects,

• Synthetic 3D accelerograms compatible with response spectra were generated in accordance with the requirements [3].

Based on these input data, the calculation of local design

spectra, considering the real geological composition at the

location of the SVP object, is carried out in the following

steps:

• Calculation of the synthetic accelerograms on the base at level -100m from the free level in accordance with IAEA [2] standards,

• Calculation of the local synthetic accelerograms and the design response spectra at level of foundation (-6.5m) and at level of the pile foundations (-18.5m) from the excitation synthetic accelerations using the program SHAKESI for original and modified geological conditions,

• Calculation of the smoothed design spectra at foundation level (-6.5m) and pile level (-18.5m) than the median values and the statistical envelope for 84.5% probability of failure is based on previous analyses for characteristic excitation frequencies.

Fig. 5: The amplification factors between the base and free field – SHAKESI.

Fig. 6: The smoothing horizontal and vertical response spectra at level -6.5m spectrum.

For these analyses, the modified SHAKESI [3] program was used to determine a best estimate of the - --- - Transformation of ground motion from free field to base level for the 1D model of the subsoil. The amplification factors of the program SHAKESI are presented in the fig.5.

- The smoothing response spectra were calculated in program SHAKESI at defined frequencies recommended by IAEA standards (Fig.6).

6. Conclusions

This paper describes the soil-structure interaction effects in the case of the nuclear fuel storage SVP during earthquake excitation. The methodology of the calculation of the soil-structure interaction effects was presented. The local design acceleration spectra were calculated considering the SSI effects used the SHAKESI program in accordance with the recommendations of the standards IAEA. The considering the local effects in accordance with the subsoil properties is very significant.

Acknowledgements

This project was permed with the financial support of the Grant Agency SR VEGA 1/0453/20.

References

[1] EPRI, A Methodology for Assessment of Nuclear Power Plant Seismic Margin, Rep. EPRI NP-6041-SL, Rev. 1, EPRI, Palo Alto, CA, (1991).

[2] IAEA, Specific Safety Guide No. SSG-9, Seismic Hazards in Site Evaluation for Nuclear Installations. International Atomic Energy Agency, Vienna, 2010.

[3] KRÁLIK, J. Safety and Reliability of NPP in Slovakia Within IAEA Project “Stress Tests”, pp. 21-36 In: Monograph, Ed. I. Major & M. Major, Wydawnictwo Wydzialu Zarzadzania, Politechniki Częstochowskiej, Częstochowa, 2015. ISBN 978-83-65179-20-3.

[4] ZOUAGHI, T. Earthquakes Tectonics, Hazard and Risk Mitigation, Monography, In Tech Open, February 1st, 2017, DOI: 10.5772/63173, ISBN: 978-953-51-2886-1.

[5] CAJKA, R., J. LABUDKOVA. Dependence of defor-mation of a plate on the subsoil in relation to the parameters of the 3D model. In International Journal of Mechanics, ISSN: 1998-4448 Volume 8, 2014.

[6] HSIUNG, S. M., H. ASADUL, A.H. CHOWDHURY, Seismic Effects on Soil-Structure Interactions, NRC–02–07–006, NRA, San Antonio, Texas, 2011.

[7] KRÁLIK, J., M. ŠIMONOVIČ, Earthquake response analysis of nuclear power plant buildings with soil-structural interaction. Mathematics and Computers in Simulation 50. IMACS/Elsevier Science B.V. 1999.

CUTE 2020 PAPER: 07



NON-MONOTONE PROJECTED GRADIENT METHOD IN LINEAR

ELASTICITY CONTACT PROBLEMS WITH GIVEN FRICTION

Lukáš POSPÍŠIL1, Martin ČERMÁK1,2, David HORÁK2,3, Jakub KRUŽÍK2,3

1Department of Mathematics, Faculty of Civil Engineering, VSB-TU Ostrava, Ludvíka Podéště 1875/17, Ostrava, Czech Republic

2Department of Applied Mathematics, Faculty of Electrical Engineering and Computer Science, VSB-TU Ostrava, 17. listopadu 2172/15, Ostrava, Czech Republic

3Institute of Geonics of the Czech Academy of Sciences, Studentská 1768, Ostrava, Czech Republic


Abstract. We are focusing on algorithms for solving large-scaled convex optimization problem in linear elasticity contact problems in 3D discretized by Finite Element methods (FEM). The unknowns of the problem are the displacements of the FEM nodes, the objective function is defined as a convex quadratic function with symmetric positive definite (SPD) stiffness matrix and the vector of forces, and the feasible set constraints the displacement subject to non-penetration conditions and/or by friction in the contact. This optimization problem is well-known as a Quadratic Programming (QP) problem and can be considered as the most basic non-linear optimization problem. Understanding these problems and the development of efficient algorithms for solving them plays the crucial role in the solution practical problems and/or in the solution of more general optimization problems resulting from other practical applications. In our contribution, we shortly review the basic theory of dualization in problems with friction. We examine the behavior and the efficiency of Spectral Projected Gradient method modified for solving QP problems (SPG-QP) on the solution of toy example in MATLAB environment.

Keywords

Contact problems, Finite Element Method, Linear

elasticity, Quadratic programming.

1. Problem definition

As a simple benchmark, we consider the block of homogeneous material has fixed zero displacement on boundary ΓD and imposed traction F on ΓF. The part ΓC denotes the part of boundary that may get into contact with rigid obstacle. The block is attracted to obstacle as

consequence of the gravity force FG, see Fig. 1.

Fig. 1: Benchmark: contact problem with rigid obstacle.

We solve discretized form of the problem using FEM (see e.g., [1]), which leads to the optimization problem

�� ≔ min�∈�12 �� − �� + �� , (1)

��(�) ≔ � ��‖��‖��

�� ,

where ! ∈ ℕ is number of used nodes and # = 3! is

number of variables, � ∈ ℝ' is a vector of unknown displacements, Ω) ∶= +� ∈ Γ) ∶ �- ≥ 00 is set of feasible �, � ∈ ℝ'×' is a symmetric positive definite (SPD)

stiffness matrix (the Dirichlet boundary condition is implemented by modifying the stiffness matrix),

� ∈ ℝ' is vector of internal forces density resulting from the stresses imposed on the structure during a displacement,

��: ℝ' ⟶ ℝ is numerical integration of functional describing the friction forces in the weak formulation of the problem,

�� ∈ ℝ��,4 are formed by appropriately placed multiples of the unit tangential vectors in such

CUTE 2020 PAPER: 07



way that the jump of tangential displacement due to displacement � is given by ��

�� ∈ ℝ is slip bound associated with �� . Additionally, we denote 5) ≤ ! as number of FEM nodes in Γ). Since our problem has simple geometry, see Fig. 2, we set # ∶= 70, 0, −18 as normal contact vector and 9 ∶= 71, 0, 08, 94 ∶= 70, 1, 08 as tangential vectors for every FEM node in Γ).

Fig. 2: Benchmark: Geometry of contact in FEM nodes.

For every contact node (i-th node of Γ)) is �� ∈ ℝ4,' given by zero matrix with 1 in first row on appropriate x-coordinate of i-th node and in second row on appropriate y-coordinate of i-th node. Additionally, we assume that

� ∶= :� � , … , �� <� is the full rank matrix.

We can modify the non-differentiable term �� in (1) into equivalent form (see [8])

��(�) = � max‖?@‖AB_� D��,��

��

where D� ∈ ℝ4 are regulation variables. We denote function and vector

E(�, F) ≔ �(�) + D��, D ≔ :D � , … , D�� <� (2) and we write constraints ‖D�‖ ≤ �_G in the form

HD4�I 4 + D4�4 ≤ �� , G = 1, … , 5J, where DK is j-th component of D. After the substitution we get

min�∈LM�(�) + ��(�)N = min�∈� sup?∈RSE(�, D). (3) (3)

We consider E(�, D) as Lagrange function and D as vector of Lagrange multipliers (in notation (2)) and we use the duality theorem (see [5]) to reformulate problem (3) and get max?∈RS

min�∈� E(�, D)

= max?∈RS,U�VW min�∈ℝX E(�, D) + F)�(Y� − Z), where we included condition � ∈ Ω) by creating new Lagrange multipliers. Matrix Y ∈ ℝ��,' and vector Z ∈ℝ�� are constructed in a such way, that the feasible set described by non-penetration condition is written in form +� ∈ ℝ' ∶ Y� ≤ Z0 = Ω) . Due to geometry in our problem we can construct Y very simply. Y is zero matrix with -1 in every i-th row (which is corresponding to i-th node in Γ[) on appropriate z-coordinate of i-th node (see choice of normal vectors for nodes in Γ)). Problem (1) is equivalent to the saddle point problem M��, FN ≔ arg maxU∈R min�∈ℝX �(�) + F)� MY_� − ZN, (4)

where

F ∶= b DF)c, Y_ ∶= b�Yc, Z ∶= bdZc

and

Λ ≔ f7D, F)8 ∈ ℝg��: hD4�I 4 + D4�4 ≤ �� ,G = 1, … , 5J, F) ≥ di.

We derive the dual problem corresponding to (4) using the first KKT condition (since stiffness matrix is SPD, we can use standard inversion �I ) in form � = �I (� − Y_ �F) and substitute into Lagrange function (2). After simplifications we get

E(�, F) = − 12 F�Y_�I ��F + F�Y_�I � − 1

2 ��I �. We obtain function of only variable F. Since we want to find maximizer (see saddle-point problem (4)), we omit the constant term and change signs. Optimal F solves equivalent minimization problem

F = minU∈R Θ(F) , Θ(F) ≔ 12 F�kF − F�l, (5)

where we denoted k ∶= Y_�I Y_ � , l ∶= Y_�I �. Obviously k ∈ ℝg��,g�� is SPD and problem (5) is QP problem with separable quadratic constraints combined with bound constraints.

2. Numerical solution

We implement and solve the problem in MATLAB. For the discretization by FEM, we adopt the open-source library presented in [11]. The inverse of the stiffness matrix in (10) is computed using MATLAB command inv. To solve the problem (5), we use SPG algorithm [3]. It is a projection gradient method with the Barzilai-Borwein (BB, [2],[10]) step-size

n�op 4 = q rn�o − s�o∇�(n�o)u, s�o: = (n�o − n�oI )�(n�o − n�oI )

(n�o − n�oI )�(∇�(n�o) − ∇�(n�oI )). However, this procedure does not necessarily provide the decreasing sequence of function values (see [6]), therefore the additional step is introduced

n�op = n�o + v�ol�o , l�o = n�opwx − n�o,

where l�o is called spectral projected gradient. The appropriate step-size v�o is computed using iterative Grippo-Lampariello-Lucidi line-search method (GLL, [7]) to satisfy so-called generalized Armijo condition �(n�o + v�ol�o) < ��z{ + Dv|⟨∇�(n�o), l�o⟩. (6) Here D ∈ (0, 1) represents a safeguarding parameter and

��z{ ∶= max ��(n�oIK): 0 ≤ � ≤ min+G9, 5 − 10� . Because of the enforcement of condition (6), the algorithm generates the sequence of approximations with decrease in of objective function in every 5 ≥ 1 iterations and the algorithm converging to the minimizer.

CUTE 2020 PAPER: 07



Recently, [9] introduced the simplification of the method in the case of the quadratic optimization problem. If the objective function is quadratic, one can derive the analytical formula for the computation of ��, which satisfies (6). The algorithm can be written with only single matrix-vector multiplication during one iteration.

3. Preliminary results

In our numerical experiment, we consider steel brick � =2 ⋅ 10�, � = 0.33, � = 7.85 ⋅ 10I4 of size 2 × 1 × 1 [m] in mutual contact with rigid obstacle. The displacement and the friction are caused by the force k = 7450, 0, 08. We consider given (Tresca) friction between the brick and the obstacle. To discretize the problem, we construct regular grid with the number of FEM nodes in axis equal to !{ = 10, !� = !- = 5. In total, we obtain ! = 396 FEM nodes, the primal problem of dimension # = 1188, the number of FEM nodes in contact 5J = 66, and dual problem of 198 unknowns. The feasible set of dual problem is composed from 66 bound constraints and 66 separable quadratic constraints.

Fig. 3: Benchmark: The non-monotone decrease of the norm of scaled

projected gradient during the solution process.

We implemented SPG-QP in MATLAB and set the parameters of Armijo criteria to recommended values 5 = 10, D = 0.9 and initial approximation equal to (feasible) zero vector. The first BB step-size is equal to steepest descent (Cauchy) step-size. We solved the problem (see Fig. 4) with coefficient of friction (slip bound) �� = 100�� , where �� is the contact surface corresponding to i-th node. Fig. 3 demonstrates the decrease of the Euclidean norm of scaled projected gradient

��(n) ≔ 1s� MqMn − s�∇�(n)N − nN,

where α� ∈ (0, 1 λ��⁄ 8 (see [4]) and λ�� is an upper estimation of the largest eigenvalue of Hessian matrix F, which we computed using Gershgorin circle theorem. The norm of projected gradient is used as stopping criteria of the algorithm.

Fig. 4: Benchmark: The solution of the benchmark.

4. Conclusion

In our work, we examined SPG-QP for solving the dual problem in linear elasticity contact problems with given friction. The preliminary results demonstrate the efficiency for dealing with this type of problems.

Acknowledgements

This contribution has been completed thanks to the financial support provided to VSB-Technical University of Ostrava by the Czech Ministry of Education, Youth and Sports from the budget for conceptual development of science, research and innovations for the 2020 year.

References

[1] ALBERTY, J., C. CARSTENSEN and S. A. FUNKEN. Remarks around 50 line of Matlab: short finite element implementation. Numerical Algorithms. 1999, vol. 20, pp. 117–137. DOI: 10.1023/A:1019155918070.

[2] BARZILAI, J. and J. M. BORWEIN. Two points step size gradient methods. IMA Journal of Numerical Analysis. 1988, vol. 8, pp. 141–148. DOI: 10.1093/imanum/8.1.141.

[3] BIRGIN, E. G., J. M. MARTINEZ and M. M. RAYDAN. Nonmonotone spectral projected gradient methods on convex sets. SIAM Journal on Optimization. 2000, vol. 10, pp. 1196–1211. DOI: 10.1137/S1052623497330963.

0 20 40 60 80 100

iterations

10-12

10-10

10-8

10-6

10-4

10-2

100

norm of projected gradient

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[4] DOSTAL, Z. On the decrease of a quadratic function along the projected gradient path. ETNA Electronic Transactions on Numerical Analysis. 2008, vol. 31, pp. 25–29. ISSN: 1068-9613.

[5] DOSTAL, Z. Optimal Quadratic Programming Algorithms, with Applications to Variational Inequalities, SOIA, Springer, New York, US, 2009. ISBN 978-0-387-84806-8.

[6] FLETCHER, R. On the Barzilai-Borwein method. In: Qi L., Teo K., Yang X. (eds) Optimization and Control with Applications. Applied Optimization, vol 96. Springer, Boston, MA, 2005, pp. 235–256. ISBN 978-0-387-24254-5. DOI: 10.1007/0-387-24255-4_10.

[7] GRIPPO, L., F. LAMPARIELLO and S. LUCIDI. A nonmonotone line search technique for Newton’s method. SIAM Journal on Numerical Analysis. 1986, vol. 23, pp. 707–716. DOI: 10.1137/0723046.

[8] HLAVÁČEK, I., J. HASLINGER, J. NEČAS and J. LOVÍŠEK. Numerical Solution of Variational Inequalities, Springer, New York, Springer Series in Applied Mathematical Sciences, 1988, vol. 66, ISBN 10: 0387965971, ISBN 13: 9780387965970, DOI: 10.1007/9781461210481.

[9] POSPISIL, L., P. GAGLIARDINI, W. SAWYER and I. HORENKO. On a scalable nonparametric denoising of time series signals. Communications in Applied Mathematics and Computational Science. 2018, vol. 13, pp. 107–138. DOI: 10.2140/camcos.2018.13.107

[10] RAYDAN, M. M. Convergence properties of the Barzilai and Borwein gradient method. PhD thesis. Rice University. 1991.

[11] CERMAK, M., S. SYSALA and J. VALDMAN. Efficient and flexible MATLAB implementation of 2D and 3D elastoplastic problems. Applied Mathematics and Computation. 2019, vol. 355, pp. 595–614. DOI: 10.1016/j.amc.2019.02.054

CUTE 2020 PAPER: 08


EVALUATION OF DIFFUSION COEFFICIENT BASED ON CHLORIDE PROFILE AND ELECTRICAL RESISTIVITY OF WASTE AGGREGATE

CONCRETE

Marie HORNAKOVA1, Tuan D. LE1, Petr LEHNER1, Petr KONECNY1

1Department of Structural Mechanics, Faculty of Civil Engineering, VŠB – Technical University of Ostrava, L. Podéště 1875/17, Ostrava-Poruba, Czech Republic


Abstract. The aim of the article is to determine the durability of structural lightweight waste aggregate concrete based on the measured chloride profile by the standardized test method NT Build 443, and to compare the results to the values measured by resistivity test that has been done previously on the same concrete mixture. In this case, the durability related to the chloride ion diffusion is investigated on the relatively new type of concrete, containing waste material – red ceramics fine aggregate, and artificial expanded clay coarse aggregate. The aggregates were fully pre-soaked before the addition into the concrete mixture, so the internal curing effect is also considered in terms of the degradation process. The diffusion coefficient obtained by the measurements is a key input parameter for modelling of the degradation process.

Keywords

Concrete, chloride ingress, chloride profile, durability, diffusion coefficient, NT Build 443, red ceramic waste aggregate.

1. Introduction

There has been a growing interest in the field of sustainability since the last decades. In terms of civil engineering, one of many problems within this field is massive amounts of demolished brickwork and concrete while manufacturing of new concrete and bricks causes the reduction of natural resources. Therefore, the recycling and reusing waste or unsuitable building materials as a total or partial replacement of traditional concrete ingredients is of highest interest and it is necessary to test these types of mixtures also in terms of durability.

The aim of the article is to observe the durability in case

of chloride diffusion of the structural lightweight concrete (SLWAC) made of waste red ceramic fine aggregate (WRCFA) and expanded clay coarse aggregate (ECCA), that has been designed and its mechanical properties were tested in previous research [1]. Results of diffusion coefficient are compared to the results computed by resistivity measurements that were done previously in [2].

Evaluation of the diffusion characteristics is important with respect to the durability of reinforced concrete placed in aggressive environment. Concrete is material that strengthens during the maturity process; therefore, the properties are time-dependent. The diffusion coefficient allows description of the penetration of chlorides in concrete and it is one of the most important input parameters of numerical model for the estimation of durability of concrete. Therefore, it is necessary to obtain the parameters of concrete sufficiently accurately and efficiently [3],[4].

2. Materials and mixture proportions

WRCFA (Figure 1a) was used as fine particles of the mixture. This aggregate was procured through crushing and grinding red ceramic debris. The debris was sourced from a local producer of airbricks. In the European Union construction elements which did not pass quality control tests are not allowed to leave the production facilities. Therefore, they are usually destroyed on-site creating huge stockpile of clean debris [5],[6]. The aggregate was clean and did not contain remains of any mortar [7].

Commercially available artificial lightweight aggregate was used as coarse aggregate. The ECCA (Figure 1b) is produced on mass scale by mixing clay and water into paste. The final particle is expanded porous clay with





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a hard shell and the pores are mostly interconnected [8].

Fig. 1: (a) Waste red ceramic fine aggregate, (b) expanded clay coarse aggregate.

The requirements for the mixture in question were very specific: using only pre-soaked lightweight aggregates (no additional water), good workability of the fresh mix, minimum voids on the surface of the sample (closed structure). These requirements were fulfilled and the whole process of designing is described in [1]. Mixture proportions are given in Table 1. The characteristics of the mixture are also described in [1]. Concrete may be classified as LC 12/13 according to [9]. Tab. 1: Mixture proportions of a cubic meter of mixture.

WRCFA

[kg/m3] ECCA

[kg/m3] Cement [kg/m3]

dry 378.38 247.07 320.49

soaked 700.71 386.05 - absorbed water 322.33 138.98 -

3. Chloride ingress into concrete

Chloride ions can migrate through the concrete as a result of a concentration gradient (diffusion), a pressure gradient causing the flow of chloride bearing solutions through pores, and capillary action. Among these transport options, the diffusion is the most damaging process in case of the initiation of corrosion of the steel reinforcement of highway structures in mild climate and marine environment. If the cracks are absent, chloride diffusion depends mostly on the nature of the porosity. Low rate of diffusion is achieved when the total volume fraction of porosity and constrictivity is low and its tortuosity is high. However, there are a lot of other parameters that influence the chloride ingress (surface chloride content, the temperature at the time of casting, the age of the structure, etc.) [4].

Only the free chloride will diffuse through the structure. If the steady-state conditions have not been reached before testing, the results may be affected. Binding capacity of the specific concrete mixture is related to the used cementitious materials. Also, the inclusion of supplementary cementitious materials may affect the binding phenomenon. so the exact influence is of interest of many research teams, e.g.[10],[11]. In this project, there has been an attempt to use WRCFA also as

a partial cementitious substitution [1].

The chloride penetration through the concrete can be generally modelled as a function of depth and time using Fick’s Second Law of Diffusion [12] – eq. 1, because, as mentioned above, the diffusion is the predominant transport mechanism of chloride into concrete [4]. This applies without distinction whether the process is in steady-state or not. 𝜕𝐶(𝑥, 𝑡)𝜕𝑡 = 𝐷c 𝜕2𝐶(𝑥, 𝑡)𝜕𝑥2 , (1)

where C(x,t) [mass %] is the chloride ion concentration at a distance x [m] from the surface of the concrete in time t [s]; Dc [m2/s] is effective diffusion coefficient, characterizing the ability of concrete to withstand the penetration of chlorides [1],[13].

Solution of the differential equation (1) with boundary conditions can be formulated by Crank’s solution – eq. (2) [13]. It is a one-dimensional model with time-independent diffusion coefficient. However, it needs to be noted that this model represents the simplification of the reality. For the estimation of the real concentration, it is necessary to consider also other factors (time dependency of diffusion parameter and surface chloride concentration, etc.) [14].

𝐶(𝑥, 𝑡) = 𝐶0 {1 − 𝑒𝑟𝑓( 𝑥√4 ∙ 𝐷c ∙ 𝑡)}, (2)

where C0 [mass %] is concentration of the chloride at the surface of the concrete and erf is the error function complement.

4. Preparation of the specimens and test methods

4.1. Preparation of test specimens

Three saturated cylindrical specimens with diameter of approximately 100 mm and height of 100 mm were used for testing by the NT Build 443 [15] 78 days after concreting. The specimens matured in the water and were kept in the water until the test started. All faces of the specimen, except the one that should be exposed, were dried at room temperature to a stable white-dry condition and given approximately 1 mm thick epoxy coating [15].

4.2. Nordtest NT Build 443

There are several methods for analysing the chloride profile; in this project, Nordtest NT Build 443 [15] was chosen. The method is applicable to test specimens from existing structures and to new samples older than 28 maturity-days. The concrete test specimens must be free from construction faults such as cavities and visible cracks. For an adequate period (but at least 35 days), concrete specimens are immersed in aqueous NaCl

(a) (b)

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solution (165g per dm3). This test is based on natural diffusion and it gives the non-steady state diffusion coefficient Dnssd. Since the suitable tool for grinding of surface of the concrete and dust collection according to NT Build 443 is not available, the process of collecting the concrete dust needed to be slightly modified. Sampling of concrete powder in layers of chloride profile is conducted by drilling. Because it is not possible to drill thin layer of concrete, the exposure time needed to be extended to 90 days to show the differences in every layer and also only 6 layers were taken instead of 8. Therefore, the specimens were 168 days old when the profile was analysed. The concentration of chloride ions in the procured concrete dust was determined by potentiometric titration [16].

When the concentration of chlorides in given depths are available, the measured chloride profile is approximated via equation (2) with the diffusion coefficient calculated by the method of least squares given by equation (3) [15].

𝑆 = ∑ 𝛥𝐶2(𝑛)𝑁𝑛=2 = ∑(𝐶m(𝑛) − 𝐶c(𝑛))2𝑁

𝑛=2 , (3)

where S [(mass %)2] is the sum of squares to be minimized, N is the number of concrete layers ground off, ΔC(n) [ mass%] is the difference between the measured and the calculated chloride concentration of the n’th concrete layer, Cm(n) [mass %] is the measured chloride concentration of the n’th concrete layer and Cc(n) [mass %] is the calculated chloride concentration in the middle of the n’th concrete layer.

It is common fact that the concrete age has a significant effect on the diffusivity [17]. In order to evaluate the precision of the method, the results tested at different age should be somehow corrected. For example, the research [18] uses equations (4) based on data taken from [17] for Portland cement concrete. 𝐷N = 𝐷𝑡( 𝑡𝑁)𝛽 , 𝛽 = 0.152(𝑤𝑐 )−0.6, (4)

where t represents the specimen age [days], N is the studied age [days] and w/c is the water-cement ratio. However, in this case, it is not possible to precisely determine the w/c parameter because only the information about water trapped in the pores of aggregate is known but the actual amount of water used for hydration of cement is undefinable.

5. Results and discussion

The results in form of surface concentration of chlorides and diffusion coefficient calculated based on the chloride profile are given in Table 2. The chloride profile and approximated curve for sample A are shown in Fig. 2. The diffusion coefficient obtained by resistivity measured in specific time points is given in Table 3. The results in the Table 3 are based on the measurements and calculation described in [2].

Based on the results, one should note that the diffusion coefficient measured by Nordtest NT 443 is higher (3.48∙10-11 m2/s in 168 days) in comparison with diffusion coefficient obtained by resistivity measurements (0.96∙10-

11 m2/s) without consideration of chloride ion activity coefficient γ1. After correction of this parameter, the result in 161 days is closer (1.38∙10-11 m2/s) to the results from chloride profiling, but still, the value of diffusion coefficient obtained by chloride profiling is almost three times higher than the value procured by resistivity measurements. Tab. 2: Surface chloride concentration and diffusion coefficient

calculated based on the data measured by NT Build 443.

Sample Surface concentration of

chlorides [mass %] Diffusion coefficient

Dc168 [m2/s]

SLWAC – A 6.82 5.19∙10-12

SLWAC – B 3.77 6.48∙10-11

SLWAC – C 5.14 3.43∙10-11

Mean value 5.24 3.48∙10-11

Fig. 2: Approximation of chloride profile for values measured in sample A.

Tab. 3: Diffusion coefficient calculated based on resistivity measurements [2].

Time [days] Diffusion coefficient Dc [m2/s]

γ1=1 γ1=0.692

7 1.64∙10-11 2.37∙10-11

14 1.43∙10-11 2.07∙10-11

28 1.40 ∙10-11 2.03∙10-11

56 1.38∙10-11 2.00∙10-11

91 1.14∙10-11 1.65∙10-11

161 0.96∙10-11 1.38∙10-11

6. Conclusions

The article deals with the evaluation of concrete material parameters related to durability. Two approaches, chloride profiling according to Nordtest NT Build 443 and electrical resistivity measurement are compared. Nordtest NT Build 443 is relatively long, requires intensive labour work and is not able to effectively capture the effect of aging of the concrete, unlike the resistivity measurements, which is a non-destructive test, so it can be repeated and it is possible to obtain a time-dependent value of diffusion coefficient.

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Measured values of diffusion properties will be used as input parameters for modelling of this specific type of concrete. However, it needs to be noted that the methods of measurement and calculation of diffusion properties would deserve an attention and possibly even modification related to the waste aggregate concrete since usually it is used for ordinary concrete mixtures. In terms of comparison of these two approaches (resistivity measurements and Nordtest NT 443), it would be also desirable to evaluate the results in the same age of concrete in order to derive the conclusion of the relation between the results and the possible differences.

Acknowledgments

The financial supports of the grant program financed by Ministry of Education, Youth and Sports of the Czech Republic through VSB – TU Ostrava (SGS SP2020/120) and the grant program „Support for Science and Research in the Moravia-Silesia Region 2018" (RRC/10/2018), financed from the budget of the Moravian-Silesian Region, are highly acknowledged.

References

[1] HORŇÁKOVÁ, M., KATZER, J., KOBAKA J., KONEČNÝ, P. Lightweight SFRC Benefitting from Pre-soaking and Internal Curing Process. Materials 2019, 12 (24), 4152. https://doi.org/10.3390/ma12244152

[2] HORNAKOVA, M., KONECNY, P., LEHNER, P., KATZER J. Durability of structural lightweight waste aggregate concrete – electrical resistivity. In: Structural and physical aspects of construction engineering: 4th international conference. High Tatras, 2019. (in print)

[3] NILSSON, L.O., E. POULSEN, P. SANDBERG, H.E. SORENSEN and O. KLINGHOFFER. HETEK, Chloride penetration into concrete. State of the Art. Transport processes, corrosion initiation and prediction models. 1996. ISBN 8774917366.

[4] DYER, Thomas D. Concrete durability. Boca Raton, 2014. ISBN 978-0415564755.

[5] SIDDIQUE, Salman, Sandeep CHAUDHARY, Sandeep SHRIVASTAVA and Trilok GUPTA. Sustainable utilisation of ceramic waste in concrete: Exposure to adverse conditions. Journal of Cleaner Production. 2019, 210, p. 246-255. DOI: 10.1016/j.jclepro.2018.10.231. ISSN 09596526.https://linkinghub.elsevier.com/retrieve/pii/S0959652618332578

[6] PACHECO-TORGAL, F., S. JALALI, Sandeep SHRIVASTAVA and Trilok GUPTA. Reusing ceramic wastes in concrete: Exposure to adverse conditions. Construction and Building Materials. 2010, 24(5), p. 832-838. DOI: 10.1016/j.conbuildmat.2009.10.023. ISSN 09500618.https://linkinghub.elsevier.com/retrieve/pii/S0950061809003602

[7] KATZER, J.; KUŹMIŃSKA, E. Optimal Composition of Blended Waste Ceramic Aggregate. In Sustainable Construction Materials and Technologies; 2016.

[8] SPRATT, B. H. Lightweight Aggregate Concrete. Civ. Eng. London 1984. https://doi.org/10.1016/0016-0032(45)90197-9

[9] EN 206-1. Performance-Based Specifications and Control of Concrete Durability. Concrete. Part 1, Specification, performance, production and conformity; 2006.

[10] THOMAS, M.D.A., R.D. HOOTON, A. SCOTT and H. ZIBARA. The effect of supplementary cementitious materials on chloride binding in hardened cement paste. Cement and Concrete Research. 2012, 42(1), 1-7 DOI: 10.1016/j.cemconres.2011.01.001. ISSN00088846. https://linkinghub.elsevier.com/retrieve/pii/S0008884611000020

[11] SAILLIO, MICKAEL, VÉRONIQUE BAROGHEL-BOUNY and Fabien BARBERON. Chloride binding in sound and carbonated cementitious materials with various types of binder. Construction and Building Materials. 2014, 68, p. 82-91. DOI: 10.1016/j.conbuildmat.2014.05.049. ISSN 09500618. https://linkinghub.elsevier.com/retrieve/pii/S0950061814005339

[12] FREDERIKSEN, JENS MEJER, LEIF MEJLBRO and LARS-OLOF NILSSON. Fick's 2nd law - complete solution for chloride ingress into concrete: - with focus on time dependent diffusivity and boundary condition. Lund, 2008. ISSN 0348-7911.

[13] M. COLLEPARDI, A. MARCIALIS, R. TURRIZUANI. Penetration of Chloride Ions into Cement Pastes and Concretes. Journal of American Ceramic Research Society. 55(10), 1972, p 534-535.

[14] POULSEN, E., and MEJLBRO, L. Diffusion of Chloride in Concrete: Theory and Application. Modern concrete technology, 2010, p. 469.

[15] Nordtest NT BUILD 443, Concrete, hardened: Accelerated chloride penetration, Espoo, Finland, Nordtest, 1995.

[16] ČSN EN 14629, Products and systems for the protection and repair of concrete structures. Test methods. Determination of chloride content in hardened concrete, Prague: ČNI, 2008.

[17] TANG, L. AND NILSSON, L.-O., ‘Chloride diffusivity in high-strength concrete at different ages’, Nordic Concrete Research. 11, 1992, p 162-171.

[18] TANG, L. and H. E. SØRENSEN. Precision of the Nordic test methods for measuring the chloride diffusion/migration coefficients of concrete. Materials and Structures. p. 479-485, 2001, (34).

CUTE 2020 PAPER: 09


PREDICTION OF FATIGUE DAMAGE BASED

ON PARALLEL ALGORITHM

Martin KREJSA1, Jiri BROZOVSKY1, Jiri KOKTAN1

1Department of Structural Mechanics, Faculty of Civil Engineering, VSB-Technical University of Ostrava, Ludvika Podeste 1875/17, 708 33 Ostrava – Poruba, Czech Republic


Abstract. Probabilistic methods allow better account of the randomness of input quantities in the design process and the reliability assessment. These computing approaches are currently enjoying an increasing popularity in civil engineering practice. New probabilistic procedures have been developing and implementing in commercial software. The main disadvantage is the inaccurate estimate of the resulting probability of failure and the high demands on computing technology and machine time. The presented DOProC method uses optimized numerical integration to calculate the probability of failure. The main improvement of this method is an increase in the accuracy of calculating the probability of failure by modification of the basic algorithm and reduction of computation time using parallel algorithm. First experience is gained in using the DOProC method on supercomputers. Probabilistic modeling and prediction of fatigue damage is one of the fields where the DOProC method is advantageously utilized and applied.

Keywords

Fatigue, steel structure, DOProC, probability of failure, parallelization.

1. Introduction

Probabilistic methods have also found their application in engineering., where a computational model includes random input variables. Each random variable in the probabilistic computations contains uncertainties which may be widely classified into two main categories: aleatoric (statistical) uncertainties of a random nature and epistemic (systematic) uncertainties that arise owing to imperfect knowledge in analysis of the solved problem. Typical sources of aleatoric uncertainties are material

properties and production and/or assembly inaccuracies in the geometry or the environment where the structure should be located. The final reliability of the structure is also affected by epistemic uncertainties which depend on the computational model used, statistical processing of input data, which also involves a human factor in the design process, and/or construction and use of the structure.

2. Introduction

The DOProC method (Direct Optimized Probabilistic Calculation) is one of many probabilistic methods which has been developed since 2002. The DOProC method uses optimized numerical integration to calculate the probability of failure. The main advantages include: the high accuracy of the failure probability calculation and the high efficiency of the calculation for many probability tasks. Principle of the method was published, e.g. in [2, 3]. If the values a1,i

1, a2,i

2, a3,i

3, ... , aj,i

j, ... , an,i

n are statistically

independent, then the probability of occurrence of value bk of histogram of resulting random variable B (e.g. reliability function Z in case of probabilistic reliability assessment) for a given combination k histogram classes of independent random variables Aj will be equal to the product of probabilities p(aj,i

j) of all intervals (classes) aj,i

j

(see Fig. 1).

Such a calculation method is much more accurate and depends only on the accuracy of the input data, its discretization and the computational error of the processor.

3. Parallel algorithm in the DOProC computation

Calculations by DOProC method can be very time consuming. Certain parts of the calculations may take




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place simultaneously. The DOProC algorithm described previously is advantageous for use on computers with two or more processor CPUs or cores. In the basic computational algorithm, it is possible to divide the total number of computational operations into as many parts as are available number of computing units. After partial calculations, the histogram of the resulting variable (e.g. reliability function Z in probabilistic reliability assessment) can be compiled from the partial results. Parts of resulting random variable histogram B are matched by choosing the same width of the intervals b1,p for all parts, ie also for the random variable histogram B, and are summed in each probability interval of all parts of histograms Bp of random variable B for p = (1, ..., p, ... , s) (see Fig. 2). This procedure ensures that the result of the calculation by parallel algorithm is identical to the unparalleled calculation.

4. Fatigue damage prediction

Computational operations running on more complex tasks, such as probabilistic prediction of fatigue damage in steel structures, can be easily adjusted to run in parallel, such as [1] or [5]. Probabilistic modeling of fatigue crack progression is based on linear elastic fracture mechanics and Paris-Erdogan’s law, e.g. see [4]. A three-point bending of cyclically stressed steel support element was chosen as a test case for parallelization (input parameters: number of load cycles per year, normal distribution,

m = 106, s = 105; initial size of fatigue crack, log-normal distribution, m = 0.2 mm, s = 0.05 mm; detectable size of fatigue crack, normal distribution, m = 2 mm, s = 0.2 mm; deterministic material characteristics m = 3, C = 2.2 ∙ 10-13 MPam m(m=2)+1 ). If two or more processors are used, then the calculation time can be shortened considerably. Different programming system has to be used for application of parallelization in DOProC method on supercomputers (e.g. in IT4Innovations national supercomputing center). MATLAB seems to be as a very advantageous software for this purpose. The algorithm of DOProC method is adapted for application in MATLAB software on platforms with more than one cores using the SPMD (Single program, multiple data) parallel programming. This is the most common method of parallel programming that enables to split up and run the same task with different input and output data on more CPUs or CPU cores. This technique can also split up data arrays, which is an important feature when the calculation runs on cluster of more computers that do not necessarily share all of the memory resources. The parallel algorithm is divided into three parts. The first part that prepares input data runs on one client worker (processing core of multicore CPU or one CPU in cluster). Then the second part runs simultaneously on all workers with different inputs and outputs. This part contains the main multiple for loop of DOProC method and it is the most intense part of processing. Finally, in the third part client collects the different outputs and compiles the partial results into the overall result.

Fig. 1: Principles of numerical operations with histograms of two uncorrelated random variables.

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Fig. 2: Principles of numerical operations with histograms of two uncorrelated random variables using parallel algorithm.

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The probabilistic reliability assessment of the load-bearing element loaded with cyclic load with respect to the occurrence of fatigue damage was made using this programming technique. There is a significant reduction in computing time (see Fig. 3) while preserving the accuracy of the solution (see Tab. 1).

Fig. 3: Parallel algorithm scaling: decrease of computing time with increasing number of processor units, input histograms described by 128 classes.

Fig. 4: Parallel algorithm scaling: decrease of computing time with increasing number of processor units, input histograms described by 256 classes.

Tab. 1: Comparison of calculation time t [min] depending on the number of cores and the number of classes in input histograms including the resulting probability of failure pf.

Number of intervals

64 128 256 1024

Core

cou

nt

Tim

e [m

in]

Prob

abili

ty o

f fa

ilure

pf

Tim

e [m

in]

Prob

abili

ty o

f fa

ilure

pf

Tim

e [m

in]

Prob

abili

ty o

f fa

ilure

pf

Tim

e [m

in]

Prob

abili

ty o

f fa

ilure

pf

1 0.39 0.0135 2.71 0.0164 21.91 0.0184 - -

3 0.13 0.0135 0.90 0.0164 7.10 0.0184 - -

6 0.08 0.0135 0.50 0.0164 3.77 0.0184 - -

9 0.07 0.0135 0.36 0.0164 2.62 0.0184 - -

12 0.06 0.0135 0.32 0.0164 2.03 0.0184 88.03 0.0199

5. Conclusion

In this paper, the improvements of the probabilistic method – DOProC that is still under development have been presented; such as more accurate estimation of probability of failure and reducing calculation time using parallelization. It turns out that the DOProC method is very suitable for solving various engineering tasks such as modelling of fatigue problems and prediction of fatigue damage. The DOProC method and its application in probabilistic prediction of fatigue crack damage can considerably improve estimation of maintenance costs for the structures and bridges subject to cyclic loads.

Acknowledgements

This contribution has been completed thanks to the financial support provided to VSB-Technical University of Ostrava by the Czech Ministry of Education, Youth and Sports from the budget for conceptual development of science, research and innovations for the 2020 year. Access to computing and storage facilities owned by parties and projects contributing to the National Grid Infrastructure MetaCentrum provided under the programme "Projects of Large Research, Development, and Innovations Infrastructures" (CESNET LM2015042), is greatly appreciated also.

References

[1] CHO, I.H. and J.F. HALL. Parallelized Implicit Nonlinear FEA Program for Real Scale RC Structures under Cyclic Loading. Journal of Computing in Civil Engineering, 26(3), 2012, pp. 356-365, DOI: 10.1061/(ASCE)CP.1943-5487.0000138.

[2] JANAS, P., M. Krejsa, J. Sejnoha and V. Krejsa. DOProC-based reliability analysis of structures. Structural Engineering and Mechanics, 64(4), 2017, pp. 413-426, DOI: 10.12989/sem.2017.64.4.413.

[3] JANAS, P., M. Krejsa and V. Krejsa. Direct Optimized Probabilistic Calculation. VSB–Technical University of Ostrava, 2015, 189 p, ISBN 978-80-248-3798-7. (in Czech)

[4] KREJSA, M., L. KOUBOVA, J. FLODR, J. PROTIVINSKY and Q.T. NGUYEN. Probabilistic prediction of fatigue damage based on linear fracture mechanics. Frattura ed Integrita Strutturale, 11(39), 2017, pp. 143–159. DOI: 10.3221/IGF-ESIS.39.15.

[5] LAN, C.M., Y. XU, C.P. LIU, H. LI, H. and B.F. SPENCER. Fatigue life prediction for parallel-wire stay cables considering corrosion effects. International Journal of Fatigue, 114, 2018, pp. 81-91, DOI: 10.1016/j.ijfatigue.2018.05.020.

CUTE 2020 PAPER: 10


COMPARISON OF DIFFERENT SUPPORT TYPES IN BENDING PROBLEM OF THE BEAM

Michaela BOBKOVÁ, Lukáš POSPÍŠIL

Department of Mathematics, Faculty of Civil Engineering, VSB Technical University of Ostrava, Ludvíka Podéště 15, Ostrava, Czech Republic


Abstract. The mathematical modelling plays a crucial role in the simulations and the development of sustainable civil engineering. In our work, we are interested in the analysis and comparison of the influence of several support types on the problem of bending of a thin beam. Here we suppose that the length of the beam is much bigger than its height. The considered load function applies to small deflections of a beam without considering effects of shear deformations. Such an example belongs to the most popular benchmarks in engineering practice and it is well known as Euler-

Bernoulli beam model. The body is fixed on one side by classic boundary condition and the second (testing) side is dedicated for testing the boundary conditions, such as non-classic boundary condition corresponding to a given rigid friction. From the mathematical point of view, we are dealing with linear differential equation of the forth order, which can be equivalently formulated as the solution of variational equation or inequality. We shortly discuss the solvability and the existence of solution in the case of the continuous formulations and the approximated problem. To solve the problem numerically, we adopt the Finite Element Method (FEM) with Hermite spline functions.

Keywords

bending of beam, Finite Element method, support

1. Problem definition

We consider a thin beam, see Fig.1. The body of length 𝑙 ∈ ℝ+ is fixed on the left side. The geometry of the beam is defined by the moment of inertia of the cross-

section 𝐽(𝑥), 𝑥 ∈ [0, 𝑙] and the material of the body is defined by the Young’s modulus of elasticity 𝐸(𝑥). For the demonstration presented in this paper, we will

consider only rectangular cross-section. On the second side of the body, we consider four types of different supports: (C1) hard fix, (C2) possible shift, (C3) possible rotation, and (C4) possible combination of the shift and the rotation (see e.g., [1]). The type of the support is defined by the given swivel 𝑔𝑀 ≥ 0 and/or given sliding friction 𝑔𝑇 ≥ 0. The problem is to find the deflection of the beam 𝑢 ∈ 𝐶4((0, 𝑙)), which is caused by the load function 𝑓 ∈ 𝐶((0, 𝑙)). The continuous formulation is given by

(1) 𝐷2(𝐸(𝑥)𝐽(𝑥)𝐷2𝑢(𝑥)) = 𝑓(𝑥) ∀𝑥 ∈ (0, 𝑙), 𝑢(0) = 𝐷𝑢(0) = 0, where 𝐷 denotes the derivative. The types of boundary conditions considered in this paper are

(C1) 𝑢(𝑙) = 𝐷𝑢(𝑙) = 0, (C2) 𝐷2𝑢(𝑙) = 0 ∧ |𝑇−(𝑢(𝑙))| ≤ 𝑔𝑇 ,

𝑔𝑇|𝑢(𝑙)| + 𝑇−(𝑢(𝑙))𝑢(𝑙) = 0,

(C3) 𝑢(𝑙) = 0 ∧ |𝑀−(𝑢(𝑙))| ≤ 𝑔𝑀 , 𝑔𝑀|𝐷𝑢(𝑙)| + 𝑀−(𝑢(𝑙))𝐷𝑢(𝑙) = 0,

(C4) |𝑇−(𝑢(𝑙))| ≤ 𝑔𝑇 ∧ |𝑀−(𝑢(𝑙))| ≤ 𝑔𝑀, 𝑔𝑇|𝑢(𝑙)| + 𝑇−(𝑢(𝑙))𝑢(𝑙) = 0,

𝑔𝑀|𝐷𝑢(𝑙)| + 𝑀−(𝑢(𝑙))𝐷𝑢(𝑙) = 0, where 𝑇 is shear force, 𝑀 is bending moment, and 𝑀−(𝑢(𝑙)) = lim𝑥→𝑙− 𝑀(𝑢(𝑥)), 𝑇−(𝑢(𝑙)) = lim𝑥→𝑙− 𝑇(𝑢(𝑥)). The weak formulation corresponding to problem (1) with condition (C1) is the elliptical variational equation. The weak formulation of the rest of problems are elliptical variational inequalities of the second type with non-

differentiable functions. For more details see [2], [3], [5], [7], [8], [9]. For example, the problem with (C2) results



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into

find 𝑢 ∈ 𝑉 such that 𝑎(𝑢, 𝑣 − 𝑢) + 𝑗(𝑣) − 𝑗(𝑢) ≥ 𝐹(𝑣 − 𝑢) ∀𝑣 ∈ 𝑉, where 𝑉 is appropriate Sobolev space (see e.g., [10]), and 𝑎(𝑢, 𝑣) = ∫ 𝐸𝐽𝐷2𝑢𝐷2𝑣 𝑑𝑥, 𝐹(𝑣) = (𝑓, 𝑣) = ∫ 𝑓𝑣 𝑑𝑥.𝑙

0𝑙

0

Please, notice that the bilinear form 𝑎 is symmetric, bounded, continuous and V-elliptical. Functional j is semi-continuous from bellow, convex and own on 𝑉. The linear functional 𝐹 is continuous (see e.g., [2], [5]).

Fig. 1: Different boundary conditions of considered beam model.

2. Finite Element method

We discretize the weak formulation using Finite Element method (FEM) based on cubic Hermite splines (piecewise cubic interpolation functions). We obtain the minimization problem with non-differentiable objective functional (in cases (C2), (C3), (C4)).

To deal with this non-differentiability, we introduce the regularization and reformulate the problem as a sequence of problems with differentiable functional.

Using this approach, we obtain the sequence of non-

linear algebraic equations (from the necessary optimality conditions), which can be solved using Newton method.

For more details see e.g., [3], [4], [6], [11].

3. Results

We implement the proposed methodology in Matlab environment and present how the boundary condition type influences the solution and the complexity of corresponding minimization problem.

Acknowledgements


References

[1] HORÁK, J. Notes on solvability of one class of semi-coercive 1D problems of the 4th order. In: ODAM1999 conference. Olomouc: 2000, pp. 98–114. (in czech)

[2] REKTORYS, K. Variational Methods in Mathematics, Science and Engineering, Springer, New York, 2001, ISBN 10: 1402002971

[3] HLAVÁČEK, I., J. HASLINGER, J. NEČAS and LOVÍŠEK J. Numerical Solution of Variational Inequalities, Springer, New York, Springer Series in Applied Mathematical Sciences, 1988, vol. 66, ISBN 10: 0387965971, ISBN 13: 9780387965970, DOI: 10.1007/9781461210481.

[4] REDDY, J. N. An Introduction to the Finite Element Method, McGraw-Hill, New York, NY, USA, 3rd edition, 2006. ISBN 9780072466850

[5] EKELAND, I. and R. TEMAM. Convex Analysis and Variational Problems, SIAM, Philadelphia, Pa, USA, 1999. ISBN 978-0-898714-50-0

[6] GLOWINSKI, R., J. L. LIONS and R. TRÉMOLIERES. Numerical Analysis of Variational Inequalities, Amsterdam, Elsevier Science, North-Holand, The Netherlands, 1981. ISBN 9780080875293

[7] LIONS, J. L. and G. STAMPACCHIA. Variational Inequalities, Communication on Pure and Applied Mathematics. 1967, vol. XX. pp. 493–519, ISSN 1097-0312

[8] AUBIN, J. P. Approximation of Elliptic Boundary - Value Problems, London, Wiley-Interscience, 1972. ISBN 0-486-45791-5

[9] FUČÍK, S. and A. KUFNER. Nonlinear differential equations, Amsterdam, Elsevier, 1980. ISBN 0-444-

41758-3, eBook ISBN 9781483278377

[10] KUFNER, A., O. JOHN and S. FUČÍK. Function spaces, Academia, Prague, 1977. ISBN 978-90-286-

0015-7

[11] CIARLET, P. G. The finite element method for elliptic problems, Amsterdam, North-Holland, 1979. ISBN 978-0-898715-14-9

https://www.bookdepository.com/publishers/Springer-Verlag-New-York-Inc

https://www.bookdepository.com/publishers/Springer-Verlag-New-York-Inc

https://doi.org/10.1007/978-1-4612-1048-1

https://blackwells.co.uk/bookshop/search/publisher/Elsevier%20Science



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A CRACK APPROACHING THE EDGE OF THE AGGREGATE

Michal VYHLÍDAL1, Jan KLUSÁK2

1Institute of Structural Mechanics, Faculty of Civil Engineering, Brno University of Technology, Veveří 331/95, 602 00 Brno, Czech Republic

2Institute of Physics of Materials, Czech Academy of Sciences, Žižkova 513/22, 616 62 Brno, Czech Republic


Abstract. In this work, the influence of a crack approaching the edge of the amphibolite inclusion on fracture behaviour of cement composite is investigated. Specimens of the nominal dimensions 40 × 40 × 160 mm with polygonal amphibolite inclusion of 8 × 8 × 40 mm were provided with an initial central edge notch with a depth 12 mm, which was made by diamond blade saw. To determine the influence of polygonal cavity on fracture behaviour, fracture tests were conducted via three-point bending. The aim of this work is to analyse the behaviour of such specimen by means of finite element method (FEM) principles in Ansys, Inc. software. For this reason, a simplified 2D model was created for plane strain conditions and based on the fracture test configuration. The crack propagation assessment was based on generalized fracture mechanics approaches using a criterion of an average value of tangential stress determined in dependence on the polar angle θ. The results of numerical analysis indicate that the debonding in the close vicinity of the bottom edge of the inclusion occurred. In other words, imperfect compaction of the fresh mixture and a smooth surface of the aggregate created poor interface with lower mechanical-fracture parameters.

Keywords

Amphibolite inclusion, Average tangential stress, Finite Element Method, Fracture Mechanics.

1. Introduction

Recent serious failures of bridges and other infrastructure buildings lead material research to reveal the conditions and causes of failure initiation. The efforts to identify mechanisms of crack formation push researchers to the studies of microstructure and how the microstructure

influences mechanical-fracture properties of structural materials. The influence of microstructure on the fracture behaviour of concrete, as one of the most used building material, has been the subject of research since the discovery of the interfacial transition zone (ITZ) by Farran [1]. The insight of ITZ’s formation and identification of ITZ’s mechanical-fracture parameters are keys to explanation of the fracture process zone formation.

2. Theoretical background

2.1. Aggregate-matrix interface

At the aggregate-matrix interface, there is a layer primarily around coarse aggregate grains or steel reinforcement with significantly different microstructure, which is formed mainly by ettringite needles and portlandite plates, than the surrounding matrix called the Interfacial Transition Zone (ITZ) [1]. Basic property of the ITZ is mainly higher local porosity, which is related to lower values of mechanical-fracture parameters of the ITZ. The ITZ can be consider as the “weakest element” [3] in cementitious composites and should form stress concentrator which determines the structure’s service life.

2.2. Fracture Mechanics

Fracture mechanics is widely used as a requisite tool to prevent and predict catastrophic failures of man-made structures. When the structural design of these structures is more difficult (e.g. new materials, difficult geometry), it is suitable to apply the principles of fracture mechanics. Fracture mechanics together with a finite element method (FEM) is a powerful tool for the assessment of structures behaviour which determines the durability within the structure’s service life.

Generalized linear elastic fracture mechanics



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(GLEFM) deals with the study of stress and displacement field in the vicinity of general singular stress concentrators (GSSC), such as bi-material interfaces, free edge singularities, etc. In this paper, the modified MTS (maximum tangential stress) criterion [4][5][6][7][8], which was designed for general singular stress concentrators, is used as a condition of stability. The stability condition is related to the average tangential stress 𝜎θθ(θ) calculated across a distance d ahead of the crack tip. The distance d is usually chosen in dependence on the mechanism of a rupture (dimension of a plastic zone or material grain size). The average stress 𝜎θθ(θ) ahead of the crack tip is given by expression: 𝜎𝜃𝜃(𝜃) = 1𝑑 ∫ 𝜎𝜃𝜃(𝑟, 𝜃)𝑑𝑟𝑑

0

The crack propagation direction is determined from the maximum of the average value of tangential stress: (𝜕𝜎𝜃𝜃𝜕𝜃 )𝜃0 = 0 ∧ (𝜕2𝜎𝜃𝜃𝜕𝜃2 )𝜃0 < 0

The critical value of tangential stress 𝜎θθ,c corresponding to the crack initiation for a crack in homogeneous material under fracture mode I is given by expression: 𝜎𝜃𝜃,𝑐 = 2𝐾Ic√2𝜋𝑑

The material ahead of the crack tip fractures when the mean value of tangential stress σθθ(θ0) exceeds its critical value σθθ,c: 𝜎𝜃𝜃 ≥ 𝜎𝜃𝜃,𝑐

3. Experimental programme

To determine the influence of the ITZ on the fracture behaviour of cement composite, the experimental programme was carried out on specially designed beam specimens with the dimensions 40×40×160 mm with polygonal amphibolite inclusion of 8×8×40 mm, see Fig. 1:. The matrix of the test specimens was manufactured from fine-grained cement-based composite [2]. The amphibolite inclusion was fixed in position in the moulds before the specimens casting by adhesive tape so the compaction could not be done by vibration.

Before fracture tests, the specimens were provided with an initial central edge notch with a depth a0 of 12 mm, which was made by a diamond blade saw. Fracture tests were conducted on these specimens via three-point bending with the incremental displacement loading and L–d (load vs. displacement, i. e. deflection at midspan) and L–CMOD (load vs. crack mouth opening displacement) diagrams were recorded. However, only a development of the load L in (kN) depending on the value of crack mouth opening displacement CMOD in (mm) are presented in this paper. See [2] for more details.

Fig. 1: Specimen geometry and the three-point bending fracture test configuration.

3.1. Results of fracture tests

Fig. 2: shows a development of the L depending on the value of CMOD recorded during fracture tests. The ascending branch is almost linear with the maximum force values between 0,47 and 0,60 kN. The descending branch contains local peaks with the maximal force values between 0,46 and 0,5 kN. These local extremes are not typical for quasi-brittle behaviour of cementitious composites and thus it is important to deal with them.

Fig. 2: Results of the fracture test – Development of the variable L (kN) depending on the value of CMOD (mm).

The observed crack propagation path during fracture test is shown in Fig. 3:. Knowledge of crack propagation path is important for the design of a numerical model and for its evaluation. It is clear from observed crack propagation that the mechanical-fracture parameters of the interface had to be lower than surrounding matrix.

Fig. 3: Crack propagation observed during fracture tests.

4. Numerical study

A simplified 2D model of plane strain conditions was created in Ansys, Inc. software. The geometry corresponds to the real specimen’s dimensions and boundary conditions, see Fig. 4:.

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Fig. 4: Simplified 2D model of the cracked specimen.

The crack was modelled as ideally sharp with highly refined mesh around crack tip with small elements in all directions, see Fig. 5:.

Fig. 5: Radial mesh around crack tip.

Due to the application of the modified MTS criterion for a crack propagation assessment, the materials were modelled as linear, elastic and isotropic. Thus, only three material parameters – Poisson’s ration ν, Young’s modulus E and fracture toughness KI,c – were required, see Tab. 1. Local mechanical properties of the ITZ, such as Young’s modulus, hardness and viscous properties, were assessed by nanoindentation technique. See [9] for more details.

Tab. 1: Overview of the material’s parameters used in the numerical model.

Layer E (GPa) ν (–) KI,c (MPa.m1/2)

Matrix 44.04 0.20 0.50

Aggregate 143 0.16 3.37

ITZ 25.39 [9] 0.20 Unknown

Steel plates 210 0.30

The force loading was applied to the top plate. When applying this force, the thickness of the model which is equal to 𝐵=1.0 m must be considered. To achieve the same stress field in model as in real experiments, the equality of stress acting on the top plate must be satisfied.

4.1. Results of numerical study

Crack propagation path is shown in the Fig. 6:. The green dashed line is for ideal bond with the fracture parameters equal to that of matrix while the red line is the crack propagation path for imperfect bond. The fracture parameter of the bond was calculated with respect to the known crack propagation path observed during fracture tests. The estimation works on the presumption that we know critical load at the right edge of inclusion and average tangential stress in the direction of the aggregate-matrix interface. The value of the fracture toughness of the ITZ was estimated as 0,37 MPa∙m1/2.

Fig. 6: Crack propagation path observed from numerical model for ideal (green dashed line) and imperfect (red line) bond.

Nevertheless, two more simplifications were done. The first one was the change of the initial central edge notch depth a0. In the previous published paper [11], it was found out that the real depth a0 is between 13 and 13.5 mm. In this model, crack depth a0 was considered as 13.25 mm. This damage is due to the small distance between the bottom edge of the amphibolite inclusion and the crack tip (front), which cannot resist the load that is caused by cutting the specimen by diamond blade saw and must inevitably lead to its partial failure. See [11] for more details.

The second simplification is connected to an initial debonding in the vicinity of the bottom edge of the inclusion. The debonding was included in the model because of imperfect compaction of fresh mixture and a smooth surface of the inclusion. Debonding of 1.2 mm was considered.

Fig. 7: Results of the FE simulation – Development of the variable L (kN) depending on the value of CMOD (mm).

Final calculated L depending on the CMOD diagram is shown in Fig. 7:. The second peak point was occurred when the crack changes the propagation direction at the right edge of inclusion.

5. Discussion

The similar results were obtained by [10]. In their case, the interface fracture was obtained by a splitting load under CMOD control. They had also performed a real-time crack propagation measurement by a high-resolution long-distance optical microscope. In the L depending on CMOD diagrams also two peaks can be distinguished as in this paper. The first peak was observed as soon as the crack initiated at the notch of the specimen. After a drop of the load, a second ascending branch was observed

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with a peak which occurred when the crack changes its propagation direction. These results are almost identical to the results of numerical simulations presented in this paper.

6. Conclusion

From the detailed numerical analysis of the described fracture test, we conclude that the process of debonding between inclusion and matrix occurred and that the actual crack depth a0 must be greater, as in the case of specimen with cavity – see [11]. In other words, the diamond blade saw damaged the specimen more than expected. This damage is due to the small distance between the bottom edge of the amphibolite inclusion and the crack tip (front), which is approximately 2.34 mm. It is obvious that such a small area above the crack tip cannot resist the load that is caused by cutting the specimen by diamond blade saw and must inevitably lead to its partial failure. Debonding is caused by smooth contact area between inclusion and surrounding matrix with poor adhesion and imperfect compaction of the fresh mixture. Fracture toughness of the interface was estimated as 0.37 MPa∙m1/2 at the most.

From the numerical analysis, we also conclude that the second peak of L depending on CMOD diagrams occurred when the crack changes the propagation direction at the right edge of inclusion.

Acknowledgements

This outcome has been achieved with the financial support of the Brno University of Technology under project No. FAST-J-20-6532.

References

[1] FARRAN, J. Contribution mineralogique a l’etude de l’adherence entre les constituants hydrates des ciments et les materiaux enrobes. Revue des Matiriaux de Construction. 1956, vol. 491, pp. 155–157.

[2] VYHLÍDAL, M., I. ROZSYPALOVÁ, T. MAJDA, P. DANĚK, H. ŠIMONOVÁ, B. KUCHARCZYKOVÁ and Z. KERŠNER. Fracture Response of Fine-Grained Cement-Based Composite Specimens with Special Inclusions. Solid State Phenomena. 2019, vol. 292, 63–68. ISSN 1662-9779. DOI: 10.4028/www.scientific.net/SSP.292.63.

[3] SCRIVENER, K. L., A. K. CRUMBIE and P. LAUGESEN. The Interfacial Transition Zone (ITZ) Between Cement Paste and Aggregate in Concrete. Interface Science. 2004, 411–421. ISSN 1573-2746.

DOI: 10.1023/B:INTS.0000042339.92990.4c.

[4] KNÉSL, Z., J. KLUSÁK and L. NÁHLÍK. Crack initiation criteria for singular stress concentrations: Part I: A universal assessment of singular stress concentrations. Engineering mechanics. 2007, vol. 14, pp. 399–408.

[5] KLUSÁK, J., Z. KNÉSL, and L. NÁHLÍK, Crack initiation criteria for singular stress concentrations: Part II: Stability of sharp and bi-material notches. Engineering mechanic. Engineering mechanics. 2007, vol. 14, pp. 409–422.

[6] NÁHLÍK, L., Z. KNÉSL and J. KLUSÁK. Crack initiation criteria for singular stress concentrations: Part III: An Application to a Crack Touching a Bimaterial Interface. Engineering mechanics. 2008, vol. 15, pp. 99–114.

[7] KLUSÁK, J., T. PROFANT, Z. KNÉSL, and M. KOTOUL, The influence of discontinuity and orthotropy of fracture toughness on conditions of fracture initiation in singular stress concentrator. Engineering mechanics. 2013, vol. 110, pp. 438–447.

[8] KLUSÁK, J., O. KREPL and T. PROFANT. Behaviour of a crack in a corner or at a tip of a polygon-like particle. Procedia Structural Integrity 2. 2016, vol. 2, pp. 1912–1919. ISSN 2452-3216. DOI: 10.1016/j.prostr.2016.06.240.

[9] ZACHARDA, V., J. NĚMEČEK, H. ŠIMONOVÁ, B. KUCHARCZYKOVÁ, M. VYHLÍDAL and Z. KERŠNER. Influence of Interfacial Transition Zone on Local and Overall Fracture Response of Cementitious Composites. Key Engineering Materials. 2018, vol. 784, pp. 97-102. ISSN 1662-9795. DOI: 10.4028/www.scientific.net/KEM.784.97

[10] VERVUURT, A. and J. G. M. VAN MIER. Fracture of the bond between aggregate and matrix: An experimental and numerical study. In: The Interfacial Transition Zone in Cementitious Composites. Haifa: E&FN Spon, 1998, pp. 51–58. ISBN 0 419 24310 0

[11] VYHLÍDAL, M. and J. KLUSÁK. The influence of polygonal cavity on fracture behaviour of concrete. Procedia Structural Integrity. 2019, vol. 17, pp. 690-697. DOI: 10.1016/j.prostr.2019.08.092.

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RELIABILITY APPROACHES AFFECTING SUSTAINABILITY IN CONSTRUCTION

Milan HOLICKY1

1Klokner Institute of the Czech Technical University in Prague, Czech Republic

[email protected]

Abstract. The most important reliability approaches affecting sustainability in construction consist of the target reliability levels, verification methods, and construction or interventions procedures. The optimum target reliability levels can be specified on the basis of probabilistic optimization considering sustainability aspects including building costs, expected economic, social and environmental consequences of possible failures. It appears that the derived reliability levels are strongly dependent on sustainability aspects and may be lower for assessment of existing structures than for design of new structures. The most efficient verification methods are based on advanced probabilistic approaches including risk assessment methods considering actual properties of the structure. It appears that the sustainability in construction may be significantly affected by the design and assessment methods.

Keywords

Reliability, sustainability, target, verification.

1. General

“Sustainability” is an extremely broad concept covering a number of objectives, vast amount of requirements and

operational principles. It is one of the most talked about

but least understood terms. There is no universally agreed

definition of what sustainability means. There are many

different views on what it is and how it can be achieved

[1,2]. Definitions of sustainability in various documents

are given somewhat general [3,4], slightly dissimilar and

do not provide clear principles for operational rules to

satisfy desired objectives [5,6,7]. In some documents the

definition is still in a state of development [8,9].

It appears that the construction sector is capable of

making a significant contribution to general sustainability

objectives, particularly due to the amount of material and

energy resources required to produce and maintain the

built environment [10]. The draft of EN 1990 from 2019

[11,12] includes the following general guidance

concerning sustainability in construction: the favourable

effects to society, environment, and economy can be

achieved by appropriate verification methods,

construction process, building materials, their

manufacture, durability, and recyclability.

2. Target reliability

The target reliability levels related to limit states and

sustainability in construction should be specified taking

into account:

• The possible consequences of failure in terms of

social, economic and environmental losses;

• The possible cause of attaining a limit state;

• Public aversion to failure;

• The expense and procedures necessary to reduce

the risk of failure.

Possible consequences of structural failure are split in

standards [11,12] into five subsequent classes, denoted

CC0 to CC4. Definitions of these classes are provided

considering all the above mentioned failure consequences

including also the aspects of sustainability in

construction.

Reliability indices 50 and approximate failure probability

Pf related to 50-year reference period and consequence

classes CC1, CC2 and CC3 are indicated in Tab. 1.

Tab. 1: Reliability levels for consequence classes CC1, CC2 and CC3.

Tentative reliability indexes 50 and approximate probabilities Pf

related to 50 years and ultimate limit states in EN 1990 [11].

CC1 CC2 CC3

Pf = 10-3

50 = 3,3

Pf = 10-4

50 = 3,8

Pf = 10-5

50 = 4,3

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Variation of the partial factor γ(β,V) for permanent load

with the reliability index β = αE βtar and coefficient of

variation V is shown in Fig.1 (here αE 0,7 is the FORM

sensitivity factor and βtar= β50).

Fig. 1: Variation of the partial factor γ(β,V) with the reliability index β

and coefficient of variation V.

Figure 1 indicates that reliability approaches may reduce

material consumption by 10 to 20 % and contribute to

sustainability in construction.

3. Main outcomes

The effects of reliability approaches to sustainability in

construction can be summarized as follows:

(1) Effects of design are mostly adverse, effects of

assessment usually positive.

(2) Significant effects of design and assessment are

revealed through:

− Consumption of resources

− Reuse of resources

− Use of renewables

− Protection of nature

(3) The reliability approaches include

− The specified target reliability

− Verification method

− Proposed materials

− Construction procedure

(4) The optimum target reliability should be

specified using probabilistic optimisation.

(5) Probabilistic verification methods are the most

effective approaches to sustainability.

(6) Advanced reliability approaches affect

consumption of resources by 10 to 20 %.

(7) Sustainability in construction is a complex task

that should be further investigated.

Acknowledgements

This study has been supported by the Czech Science Foundation under Grant 20-01781S and by the Ministry of Education, Youth and Sports of the Czech Republic under Grant LTT18003.

References

Brundtland Report for the World Commission on

Environment and Development, 1992

Kibert Charles J 1994 Principles and Model of

Sustainabile Construction. First International

Conference on Sustainable Construction, Tampa,

Florida

Kibert Charles J, 2008 Sustainable Construction,

Green Building Design and Delivery. JOHN

WILEY

ISO 15392: 2008, Sustainability in Building

Construction – General Principles.

fib Bulletin 65 2010 Model Code, Final draft –

Volume 1

Sakai K et al. 2016 Sustainability design of concrete

structures, Structural Concrete 17, No. 6, Berlin

Holický M 2009 Reliability analysis for structural design. Stellenbosch: SUN MeDIA

Holický M 2013 Introduction to Probability and Statistics for Engineers. Heidelberg: Springer

Hajek P et al. 2013 Life-cycle assessment of RC

structures in Czech regional conditions, Life-

Cycle and Sustainability of Civil Infrastructure

Systems – Strauss, Frangopol & Bergmeister

(Eds), London

CEN Technical Specification 2018 Assessment of

existing structures. CEN/ TC250

EN 1990 2002 Eurocode — Basis of structural and

geotechnical design

prEN 1990 2019 Eurocode — Basis of structural

and geotechnical design

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UNCERTAINTY IN NDT ASSESSMENTS OF HISTORIC STEEL BRIDGES

Miroslav SÝKORA1, Jan MLČOCH1, Pavel RYJÁČEK2

1Department of Structural Reliability, Klokner Institute, CTU in Prague, Šolínova 7, Prague, Czech Republic 2Department of Steel and Timber Structures, Faculty of Civil Engineering, CTU in Prague, Thákurova 7, Prague, Czech

Republic


Abstract. Sustainable development can be supported by extending service lives of existing bridges. Preservation and upgrades should be based on improved structural assessments, monitoring and strengthening methods. In the case of metallic materials, hardness methods (NDT) calibrated by a few tensile tests (DT) were shown to be associated with reasonable measurement uncertainty. This contribution discusses the current practice in NDT assessments and introduces the hierarchical modelling of the measurement uncertainty in hardness tests. Based on a limited database, preliminary results concerning measurement uncertainty in hardness methods suggest that variability of a material property can hardly be estimated on the basis of NDTs only. Systematic component of measurement uncertainty has a lower coefficient of variation (3%) than the random component (8%); the variability of the latter may thus often exceed the variability of ultimate strength of a homogeneous material.

Keywords

Existing bridges, structural assessment, hardness methods, hierarchical modelling, measurement uncertainty.

1. Introduction

The consideration of sustainability aspects in the construction sector jointly with significant economic interests resulted in adding the assessment and retrofitting of existing structures into the revision of Eurocodes [1]. Under this highly prioritised work item, new European technical rules for the assessment were developed [2] and are intended to become a part of presently revised EN 1990 for basis of design.

For bridges, sustainable development can be supported by using existing lines and crossings, and this leads to the urgent need for extension of service lives of existing bridges [1]. Preserving and upgrading of existing bridges should be based on improved structural assessments, monitoring and strengthening methods [3].

In the case of historic steel (metal) bridges, the considerable scatter of mechanical properties and unavailable design documentation necessitate tests and measurements to obtain sufficient information for structural assessments [4] and [5]. The use of various non- or minor-destructive tests (NDTs) is often preferred over to destructive tests (DTs) to reduce the cost of structural survey and damage to the structure.

For metallic materials, hardness methods were shown to be associated with reasonable measurement uncertainty and may provide a useful input for structural assessments [6] and [7]. To avoid gross errors in NDT results, structure-specific calibration of NDTs is needed by at least one tensile test (DT) [8].

While the calibration based on a few DTs reduces the systematic component of NDT measurement uncertainty, the random component (aleatory component in the modelling framework adopted here) cannot be eliminated. Taking a starting point in the previous studies [6] and [7], this contribution discusses the current practice in NDT assessments, introduces a hierarchical modelling of the measurement uncertainty in hardness tests, and quantifies its systematic and random components. The analysis is based on a database of pairs of NDTs and DTs taken from eight historic bridges built in the early 20th century.

2. Experimental database

The database contains 32 pairs of ultimate strength values




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based on NDTs and DTs, taken from eight railway bridges. The test methods are as follows:

• DT results are based on the tensile test according to ISO 6892 for tensile testing of metals under normal temperatures. The test uncertainty is negligible (coefficient of variation, “CoV”, V < 1%) [9].

• The hardness method according to Leeb considering empirical relationship to convert hardness values to ultimate strength estimates.

The materials under investigation include historic steels (no wrought irons); the materials are assumed to provide a homogeneous sample for the investigation of measurement uncertainty.

3. Current practice

When material strengths are estimated from NDTs, it is a common practice to calibrate the mean of NDTs by the mean of a few DTs and to assume that standard deviation of NDTs, σNDT, is representative (or conservative) estimate of the scatter of ultimate strength, σDT. Fig. 1 shows sample standard deviations [10] obtained from NDT and DT results for each of the eight bridges in the database.

Fig. 1: Sample standard deviations obtained from NDT and DT results for each of the eight bridges in the database.

It appears that σNDT underestimates σDT in half of the cases and provides a rough approximation of σDT only. It is emphasised that this finding is only preliminary – the database is small and for each of the bridges, the two standard deviations are estimated on the basis of only four measurements on average.

4. Hierarchical model of measurement uncertainty

4.1. Systematic and random components

It is assumed that an NDT result equals to a DT outcome affected by Θran (component of measurement uncertainty Θ random for each measurement) and Θsys (error systematic for a NDT survey of a particular structure).

Measurement uncertainty depends on the combined effect of the imprecision of the technique, device and their application. Based on the authors’ experience with hardness tests, the factors influencing measurement uncertainty might be classified as follows:

- Dominantly affecting Θran:

• Between structural members - stiffness and mass of the specimen (an NDT should be applied in the stiff and heavy areas, preferably stiffened by stiffeners or close to them; the testing of thin plates far from stiffeners must be avoided).

• Between structural members – partly also the slope of the investigated member (horizontal vs. vertical measurements though commonly compensated or eliminated when converting hardness to strength by modern devices).

• Homogeneity of hardness of the material (the outer parts of plates have higher strength and hardness than the inner parts due to the rolling).

- Affecting both Θsys and Θran:

• Skills and experiences of the worker

• Quality of the specimen surface (it must be properly grinded to a smooth surface)

This study is focused on statistical uncertainty, i.e. uncertainty in model parameters – probabilistic distribution parameters. Other parameters, deemed to dominantly affect Θsys, are disregarded in the following analysis. These include repeatability of the testing device (proper calibration of the device), number of measurements and possible elimination of extreme values from the sample to estimate hardness in a location.

4.2. Model For a bridge i and NDT measurements ndtij taken at the bridge, a probabilistic distribution of DT resulting from a particular NDT outcome is:

θsys,i ~ LN(µsys, σsys), (1)

θrnd,ij ~ LN(µrnd, σrnd), (2)

ndtij = θsys,i θrnd,ij dtij ~ LN(θsys,i µrnd, θsys,i σrnd) dtij (3)

Using capital letters to denote distributions of random variables (also as in Section 4.1) and lower-case letters to denote particular realizations of the distributions in Eq.

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60 70

σNDT

[MPa]

σDT

[MPa]

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(1) to Eq. (3), the following notation applies:

• Θsys is the distribution same for all the bridges and θsys,i is its random realization for bridge i;

• Θran is the distribution identical for all NDTs and all bridges and θrnd,ij is its random realization;

• LN denotes the lognormal distribution and μ and σ are its mean and standard deviation, respectively;

• dtij is a random realization of the material property (true value).

In Fig. 2 the DT to NDT ratios are plotted. The short horizontal lines indicate the mean ratio for a particular bridge. In the presented simplified approach, each short line thus represents a realisation θsys,i and the scatter of the dots around a respective line is indicative for Θran.

Fig. 2: DT to NDT ratios – illustration of systematic and random components of the measurement uncertainty (the dotted lines separate measurements for different bridges).

The eight observations of Θsys leads to the estimate of the mean µΘsys ≈ 1.03 and a low coefficient of variation VΘsys ≈ 2.7%. Analysing the 32 observations available for the random component, it turns out that it is unbiased and has a higher coefficient of variation VΘran ≈ 7.8%. This finding is consistent with that made in Section 3 – while the bias in NDTs can be corrected by calibration considering DTs, the random component of measurement uncertainty is quite significant and exceeds the variability of ultimate strength of a homogeneous material in common cases.

More refined analysis of measurement uncertainty, based on desired extension of the database, may provide background information for investigation of the efficiency of calibration by DTs. Related uncertainties can then be quantified and considered in the framework of the partial factor method.

5. Discussion

Based on a limited database and using a simplified approach, this contribution provides only the first insight into the hierarchical modelling of measurement uncertainty in hardness tests.

One of the issues that needs to be further explored is the effect of within-structure non-homogeneity on measurement uncertainty. It is widely recognized that as a result of production process, different strengths are commonly observed for rolled sections and plates. The first analysis suggests that slightly higher coefficient of variation is obtained for plates, but further investigations are needed to confirm this finding.

Besides desired extension of the database, future research should provide answers to the following questions:

• Can different hardness test methods (static or dynamic) be described by the same model for measurement uncertainty?

• Is the multiplicative format for Θ—see Eq. (1) and (2)—appropriate, or should the additive format or their combination be preferred?

• Can the random and systematic components of measurement uncertainty be described by same distributions for various structures?

• What is statistical uncertainty in Θsys and Θran using the frequentist or Bayesian approach?

6. Conclusion

As the present study is based on a limited database, only preliminary results concerning measurement uncertainty in hardness methods for metallic materials are provided:

• Variability of a material property can hardly be estimated on the basis of NDTs only.

• Systematic component of measurement uncertainty is found to have a lower coefficient of variation (3%) than the random component (8%). The variability of the latter may thus often exceed the variability of ultimate strength of a homogeneous material and the efficiency of calibration by DTs can be doubtful.

• The topics of further research include investigations into the effect of within-structure non-homogeneity on measurement uncertainty, uncertainties in various NDT methods, and appropriate approach to hierarchical modelling and to statistical inference.

0.8

0.9

1.0

1.1

1.2

1.3

1.4

0 10 20 30 40

DT/NDT

measurement no.

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Acknowledgements

This work study was supported by the Ministry of Culture of the Czech Republic under Grant DG18P02OVV033 ‘‘The Methods for Achieving the Sustainability of Industrial Heritage Steel Bridges”.

References

[1] LÜCHINGER, P., J. FISCHER, C. CHRYSOSTOMOU et al. New European Technical Rules for the Assessment and Retrofitting of Existing Structures (JRC Science and Policy Report). JRC, 2015. 125 pp. ISBN 1018-5593. DOI: 10.2788/095215.

[2] CEN/TC250/WG2. Assessment of Existing Structures (draft of the technical specification, Mar 2019, CEN/TC 250 N 2176). CEN TC250/ WG2, 2019. 54 pp.

[3] BIEN, J., L. ELFGREN and J.(.). OLOFSSON. SUSTAINABLE BRIDGES. Assessment for Future Traffic Demands and Longer Lives. Wroclaw: Dolnoslaskie Wydawnictwo Edukacyjne, 2007. 490 pp. ISBN 978-83-7125-161-0.

[4] MACHO, M., P. RYJACEK and J.C. MATOS. Static and Fatigue Test on Real Steel Bridge Components Deteriorated by Corrosion. Int.J.Steel Struct. 2019, Vol. 19, Nr. 1, pp. 110-130. DOI: 10.1007/s13296-018-0099-6.

[5] RYJACEK, P. The diagnostic techniques for the assessment of the historical steel bridges. In IABSE Symp. 2019. 2019, pp. 1651-1657.

[6] SYKORA, M., J. MLCOCH and P. RYJACEK. Uncertainties in Characteristic Strengths of Historic Steels Using Non-Destructive Techniques (in press). Transactions of the VSB - Technical University of Ostrava, Civil Engineering Series. 2020, pp. 6. ISSN 1804-4824 (Online), 1213-1962 (Print).

[7] LENNER, R., P. RYJACEK and M. SYKORA. Resistance Models for Semi-Probabilistic Assessment of Historic Steel Bridges (in press). In Proc. IABSE Symposium 2020. Zürich: IABSE, 2020, pp. 8.

[8] ISO 13822. Bases for design of structures - Assessment of existing structures. Geneve, Switzerland: ISO TC98/SC2, 2010. 44 pp.

[9] SYKORA, M. and M. HOLICKY. Assessment of Uncertainties in Mechanical Models. Appl Mech Mater. 2013, Vol. 378, Nr. 13, pp. 13-18. ISSN 16609336, ISBN 978-303785795-3. DOI: 10.4028/www.scientific.net/AMM.378.13.

[10] HOLICKY, M. Introduction to Probability and Statistics for Engineers. Berlin: Springer-Verlag,

2013. 181 pp. ISBN 978-3-642-38299-4. DOI: 10.1007/978-3-642-38300-7.

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BIAXIAL TESTING PROCEDURE OF TEXTILE MATERIALS IN MEMBRANE STRUCTURES

Nela FREIHERROVÁ1, Martin KREJSA1

1Department of Structural Mechanics, Faculty of Civil Engineering, VŠB – Technical University of Ostrava, L. Podéště 1875/17, Ostrava – Poruba, Czech Republic


Abstract. The aim of the article is to perform numerical simulation of biaxial testing of textile material, which is used for design of membrane structures. Membrane structures are becoming more popular owing to their potential for use in structures with higher aesthetic claims. Thanks to the use of membrane structures it is possible to achieve very low weight of the construction itself, shape variability, aesthetic airiness and large span. However, the design of membrane structures faces some challenges related to its specific properties. In order to exploit the full potential of the membrane structures, it is necessary to have knowledge about material characteristics of the used textile materials. The design is very closely related to the initial pre – stressing which is introduced into the membrane fabric. For proper modeling it is necessary to choose a suitable material model. However, these materials are characterized by nonlinear and anisotropic behavior, that is why the material models used in software are simplified. In order to create a more accurate material model, it is necessary to know the material characteristics obtained by biaxial measurement.

Keywords

Membrane structures, textile materials, orthotropic materials, biaxial testing, material characteristics, numerical simulation, RFEM software.

1. Introduction

Material characteristics determined from biaxial tests are highly dependent on the testing methodology and the subsequent evaluation of experimental data. The biaxial tests of textile materials performed so far differ depending on the chosen procedure of the institute [1 - 6]. In the Brussels experiment, the effect of applied load ratios was investigated [1, 2]. A different number of cycles for

loading ratios [2] was also investigated, or the loading was controlled by a pre-determined value of strain [3]. The results of the experiments show large differences in the obtained values of material characteristics.

Currently, there is only one standard from Japan [7] which is often considered to be the starting point in establishing the testing procedure.

2. Textile membrane materials

The materials used for the membrane structures are made by weaving fibers in 2 perpendicular directions, warp and weft (see Fig. 1).

Fig. 1: Structure of membrane materials [8].

The fabric structure is given by the number of fibers per cm and the weaving pattern. The main type of patterns for weaving textile membrane materials are (see Fig 2):

• Plain pattern,

• Panama pattern - in this case, you should look at the camera's smaller wrinkles.



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Fig. 2: The most used weaving patterns [9].

Today's used textile membrane materials are usually made from woven fabrics which are woven in 2 directions and usually supplemented with a surface treatment. The composition of the individual layers can be seen on Fig. 3.

Fig. 3: Composition of individual layers of membrane fabric [8].

The monolayer membrane materials used today are typically made of polyester, PTFE, or glass or aramid fiber materials. Polyesters (or other fibers) provide stiffness and strength of the material. They are complemented with a PVC, PTFE, or silicone coating to protect against UV radiation and other atmospheric influences.

Depending on the manufacturer, material characteristics in different scales are given for both PVC / PES and PTFE / glass materials.

For PES fabrics with PVC coating layers, 5 classification classes (1-5) are specified. Classes are divided by surface weight, yarn linear density, tensile strength (warp / weft), trapezoidal test (warp/weft), yarn number per cm (warp/weft).

PTFE coated glass fabric fabrics are divided into 7 types, G1 - G7 according to their characteristics by tensile strength (warp/weft), filament diameter, surface weight, and trapezoidal test (warp/weft).

3. Biaxial testing

When designing a membrane structure, it is very important to know the following material characteristics which greatly affect the resulting behavior and stresses in the structure:

• stiffness in warp / weft direction,

• lateral extension,

• shear stiffness.

When performing biaxial tensile tests, the membrane fabrics exhibit highly non-linear and anisotropic behavior, which strongly depends on the warp / weft load ratios and the loading history. In general, a safety factor of 5 is used. The prestress is normally about a 1/5 – 1/10 of the working stress since it can depend on the curvature of the surface and the orientation of the weave. Thus, the prestress is about 1/25 of the uniaxial strength which should be determined before the biaxial tests. However, the final values and procedure should always be discussed in accordance with the design engineer’s analysis and may vary from case to case [9].

For safety reasons, the highest possible load is always used, but it should be remembered that such high values occur very rarely in the structure. Therefore, in biaxial tests, it is enough to select the upper limit as 80% of the working stress.

During biaxial tests, one direction (warp/weft) is loaded after the fabric is pre – stressed. This procedure is then reversed, the first chosen direction is relieved, and the load is transferred to the second direction. The output of the loading process is stress – strain diagram. From the experimentally measured data and stiffness matrix for the orthotropic material, the material characteristics can then be obtained [9].

4. Numerical simulation of biaxial loading

The biaxial test of the fabric was modelled using RFEM software. The RFEM software includes a special ad-on module for designing and modelling membrane structure, RFEM Form – Finding.

The geometry of the cross-section is shown on Fig. 4.

Fig. 4: Sample geometry for biaxial test simulation [3].

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An orthotropic material with thickness 0.56 mm was chosen. The Modulus of elasticity in the warp direction is Ex = 1468 MPa and in the weft direction Ey = 1025.8 MPa. The Poisson's ratios are νxy = 0.238 in the warp direction and in the weft direction νyx = 0.166.

At first, an initial pre-stress is introduced into the sample, which can be generated by force or by deformation. For this case, the initial deformation was chosen.

The values of initial pre-stress are most often in the range of 1 - 5 kN/m [10], this value of pre-stress was caused by a deformation in the warp and weft direction of 0.1 mm (see Fig. 5).

Fig. 5: Initial pre-stressed sample with deformation in warp and weft direction 0.1 mm.

Then, 3 more load cases were created. Gradually, deformations (0.3 mm, 0,5 mm, and 1 mm) were introduced into the sample only in the weft direction while the initial value of the inserted deformation 0.1 mm was kept in the warp direction.

The loading process for this case could be carried out as follows (see Fig. 6.):

Fig. 6: Cyclic loading in the weft direction.

Then, the situation switched. In the weft direction, the initial value of inserted deformation of 0.1 mm was kept and the deformation in the warp direction was increasing

gradually in values 0.3 mm, 0,5 mm, and 1 mm.

The loading process for this case could be carried out as follows (see Fig. 7.):

Fig. 7: Cyclic loading in the warp direction.

5. Results

Figures 7, 8 show the results of the main internal forces for the last load case with the inserted deformation of 1 mm in the warp direction (see Fig. 8) and the inserted deformation of 1 mm in the weft direction (see Fig. 9) while in the opposite direction is kept with the initial inserted deformation in value of 0.1 mm.

Fig. 8: The main internal forces for sample with inserted deformation 1 mm in the weft direction.

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Fig. 9: The main internal forces for sample with inserted deformation 1 mm in the warp direction.

It can be seen from the resulting main internal forces that the sample is more sensitive to warp loading, where the internal forces are significantly higher than for the weft loading.

When designing a membrane structure, the choice of pre - stressing can significantly affect the behavior of the structure [11].

6. Conclusion

The article deals with the topic of the biaxial testing procedure of textile materials, which are used for the design of membrane structures. Since there is no worldwide recognized standard for test procedures and determined results may vary based on the institute, there is a lot of space for research. The resulting courses of internal forces and stresses will be used for comparison with laboratory testing which would lead to determine needed material characteristics – Modulus of elasticity Ex, Ey and Poisson’s ratio νxy, νyx. Due to the complexity of manufacturing the biaxial device, the experiment will be performed using a specially modified uniaxial device. The determined material characteristic should be used for creating special materials models for numerical software. More accurate material models can lead to a more efficient design of membrane structures and therefore to more economical usage of the material and creation of a more sustainable structure.

Acknowledgements

The financial supports of the grant program financed by Ministry of Education, Youth and Sports of the Czech Republic through VSB – TU Ostrava (SGS SP2020/102) and the grant program „Support for Science and Research in the Moravia-Silesia Region 2018" (RRC/10/2018), financed from the budget of the Moravian-Silesian Region, are highly acknowledged.

References

[1] VAN CRAENENBROECK, M., PUYSTIENS, S., VAN HEMELRIJCK, D., MOLLAERT, M. Biaxial testing of fabric materials and deriving their material properties – A quantitative study. Proceedings of the International Association for Shell and Spatial Structures. Amsterodam, 2015.

[2] VAN CRAENENBROECK, M., MARIJKE, M., DE LAET, L. The influence of test conditions and mathematical assumptions on biaxial material parameters of fabrics. Engineering Structures. 2019, 200(1). DOI: https://doi.org/10.1016/j.engstruct.2019.109691.

[3] BECCARELLI, P., COLSANTE, G., NOVATI, G., STIMPFLE, B., ZANELLI. A. Strain-controlled biaxial tests of coated fabric membranes 2013.

[4] UHLEMANN, J., STRANGHÖNER, N. Refined Biaxial Test Procedures for the Determination of Design Elastic Constants of Architectural Fabrics. Procedia Engineering. 2016, 155, 211-219. DOI: https://doi.org/10.1016/j.proeng.2016.08.022

[5] AMBROZIAK, A. Mechanical properties of Precontraint 1202S coated fabric under biaxial tensile test with different load ratios. Construction and Building Materials. Elsevier, 2015, 80, 210-224. DOI: 10.1016/j.conbuildmat.2015.01.074

[6] GALLIOT, C., LUSHINGER, R., H. Determination of the response of coated fabrics under biaxial stress: Comparison between different test procedures. Proceedings of Structural Membranes 2011, Barcelona, 2011.

[7] Membrane Structures Association of Japan, Testing Method for Elastic Constants of Membrane Materials (MSAJ M-02-1995), 1995.

[8] RIVERA, R., Membrane Structures: First Steps Towards Form Finding. Membranas Estructurales, 2014. ISBN 9780986324710.

[9] FORSTER, B., MOLLAERT, M. European Design Guide for Tensile Surface Structures. TensiNet, 2004. ISBN 90 8086 871 x.

[10] KOPRIVA, M., NETUSIL, M., ACHTEN, H., HIRNSAL, Z. Membrane Architecture. CTU in Prague, 2015. ISBN 978-80-01-05693-6 (in Czech).

[11] LANG, R., NĚMEC, I., ŠTEKBAUER, H. Navrhování tvarů membránových konstrukcí a výpočet střihových vzorů. TZB-info, 2017, no. 0, p. 1-9. ISSN: 1801-4399.

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NON-TRADITIONAL GEOMETRY OF WEDGE-SPLITTING TEST

Tereza JUHÁSZOVÁ1, Petr MIARKA1,2, Stanislav SEITL1,2, Ildikó MERTA3

1Institute of Structural Mechanics, Faculty of Civil Engineering Brno University of Technology; Veveří 331/95, 602 00 Brno, Czech Republic

2Institute of Physics of materials, Czech Academy of Sciences Žižkova 513/22 616 62, Brno, Czech Republic 3Research Centre of Building Materials, Material Technology, and Fire Safety Science, Faculty Civil Engineering,

Technical University of Vienna, Austria


Abstract. The wedge-splitting test is widely used in testing of fracture mechanical parameters of concrete of concrete like materials. This test enables a stable crack propagation which was analysed on cube specimen. Another interesting application for measuring fracture mechanical properties is a combination of wedge-splitting test with a three-point bending test. In this contribution we analyse the stress fields in such a non-traditional geometry of wedge-splitting test by employing a linear elastic fracture mechanics.

Keywords

Stress Intensity Factor, T-stress Linear Elastic Mechanics, WST, Finite Element Method.

1. Introduction

The wedge-splitting test (WST) [1] (See Fig.1(a)) is widely used in a testing of fracture mechanical parameters of concrete of concrete like materials. This test enables a stable crack propagation which was analysed on cubes specimen. Which gives an effective use of tested material. The WST was analysed by many studies [2][3][4], thus it is well acknowledged test among the researcher.

Another widely used test with reliable results used for evaluation of fracture mechanical properties is three-point bending test (3PBT) [5]. This test is less effective of used material during the testing.

On the other hand, an interesting application for measuring fracture mechanical properties is a combination of wedge-splitting test with a three-point bending test. This non-traditional geometry test enables more stable testing as the crack propagates from both notches simultaneously. The analysed geometry is shown in Fig.1(b) In this

contribution we analyse the stress fields in such a non-traditional geometry of wedge-splitting test by employing a linear elastic fracture mechanics (LEFM).

(a)

(b) Fig. 1: Sketch of traditional WST geometry(a) and non-traditional

3PBT with wedge and two cracks (b).

The objective of this contribution is to analyse and quantify the influence of this non-traditional geometry of WST test with three-point bending test. For this a numerical parametric study was done in a finite element method software Ansys.

2. Theoretical Background

This contribution is based on the LEFM concept, which describes the stress fields in crack body. For this




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description a Williams expansion [6] is used which can be expressed as: 𝜎𝑖,𝑗 = ∑ 𝑛2 𝐴𝑛𝑟(𝑛2−1)𝑓𝑛𝐼(𝑟, 𝜃)∞

𝑛=1 (1)

where i,j is the stress tensor, An is the coefficient corresponding to mode I, r and are the polar coordinates, n is the order of the term and the fn

I(r,) is the known geometry function. The SIF for crack opening mode I can be described [7] as:

𝐾I = 𝜎𝑎𝑝 √2𝜋𝑎𝑌𝐼 (2)

where KI is the stress intensity factor for mode I, where σapp is the applied stress, a is the crack length and YI is the geometry function.

Another parameter describing the stress fields is the T-stress which is the second term of Williams expansion and can be calculated as:

𝑇 = 𝛽𝐾𝐼√𝜋𝑎 (3)

where KI is the stress intensity factor evaluated from eq. 1 and is the biaxiality parameter which again depends on the tested geometry.

Acknowledgements

The financial support of the grants No. FAST-J-20-6341 and 8J2OAT013 is greatly appreciated.

References

[1] E.K. Tschegg, Republic Österreich. Patent number 390328B, (1986)

[2] E. Bruhwiler, F.H. Wittmann, The wedge splitting test: a new method of performing fracture mechanics tests, Engineering Fracture Mechanics, 35, (1990), 117–125

[3] I. Merta, E.K. Tschegg, fracture energy of natural fibre reinforced concrete, Construction and Building Materials, 40, (2013), 991–997

[4] S. Seitl, V. Veselý, L. Řoutil, Two-parameter fracture mechanical analysis of a near-crack-tip stress field in wedge splitting test specimens, Computers and Structures, 89, (2011), 1852–1858

[5] Rilem, Recommendation, Determination of the fracture energy of mortar and concrete by means of three-point bend tests on notched beams, Materials and structures, 18 (1985) 285-290.

[6] M.L. Williams, On the stress distribution at the base of a stationary crack, Journal of Applied Mechanics, 24 (1975), 109–114

[7] TADA, H., PARIS, P.C. and IRWIN, G.R. (2000) The stress analysis of Cracks Handbook, New York

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CEMENTITIOUS BINDER MORTARS PRINTING TECHNOLOGY – 3D PRINTER CONSTRUCTION

Dawid GIEROŃ, Tomasz PONIKIEWSKI, Jakub AUGUSTYN

Department of Process Engineering and Building Physics, Faculty of Civil Engineering, Silesian University of

Technology, Akademicka 5, 44-100 Gliwice, Poland

Liquid Admixtures Line Sales -Technical Manager, MAPEI Polska, ul. Gustawa Eiffela 14, 44-109 Gliwice


Abstract. The aim of presented work was to construct and test a 3D printing device for cementitious binder mixtures. In the article the process of making printer and following modifications of the printer, that resulted in construction the device able to produce reproducible prints, were described. For the device tests various cementitious binder mixtures were prepared. Tests of rheological and strength properties of mortars and prints in this paper were also described.

Keywords

3D printing technology, cementitious binder, mortar.

1. Introduction

The point of 3D concrete printing technology is laying subsequent layers of concrete mix on top of each other with the help of a printer nozzle [1]. The two most important features of this type of mortar are: pumpability, i.e. the ability of the mixture to transport inside the printer and to being extruded through its nozzle continuously, and buildability, i.e. the ability to form desired shapes without significant deformations [2,3]. The devices constructed by the researchers differ primarily in the way the mortar is put in motion. The device presented in this work was made with the use of machine parts for making plaster in construction industry. Mortars proposed and tested during the work were used to make test prints to verify the device made.

2. Preparation and testing of mortars for 3D printing

Four mortar mixes were proposed. They contained a large amount of cement and fine particles contained mainly in mineral additives, which made them pumpable. In order to maximize the efficiency of the printing process, a superplasticizer with an accelerating effect was added.

The selected properties of the mortars were tested according to the following procedure. Firstly, dry ingredients were mixed. Then water and superplasticizer were added and mixed altoghether for 2.5 minutes. Immediately after mixing, tests were carried out using a mortar flow table in accordance with [4]. Then, the pumpability and bulidability was tested. To test these two properties printed samples were made with an extruder (Fig. 1).

Fig. 1: Extruder and test print.




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3. Printer construction and modifications

A 3D printer conception was proposed. First idea was to construct a container in the form of a cuboid, placed directly on the endless screw (Fig. 2). However, the mortar pressure generated by the device turned out to be too low – mortar could not be extruded through the nozzle.

Fig. 2: 3D printer – version 1.

It was decided that a good solution to this problem would be the use of a special type of pump in the device, in which the steel rotor rotates in a tightly fitting, flexible, rubber-made stator (Fig. 3).

It was also necessary to place the chain transmission between the electrical engine and the device and make the device upright (Fig. 3).

Fig. 3: 3D printer - final version (left side); sator and rotor (right side).

4. Tests of printing device

Print tests were carried out using four mortar mixes. Their printing, despite some technical problems, proved to be possible (Fig.4). During the work, printed samples were made to perform strength tests of hardened concrete.

Fig. 4: 3D print – sample.

5. Conclusion

Subsequent modifications of the printer and improved, more stable cementicious mixes made printing process highly repeatable. Prints were made up to 10 layers of mortar. It was possible to make strength samples from printed concrete.

References

[1] Buswell R.A., Soar R.C., Gibb A.G.F., Thorpe A.: Freeform Construction: Mega-scale Rapid Manufacturing for construction. Automation in Construction, nr 16, 2007, pp 224–231

[2] Le T. T., et al: Mix design and fresh properties for high-performance printing concrete. Materials and Structures, nr 45, 2012, pp 1221–1232.

[3] Neralla V. N., et al: Technologia druku przestrzennego dla placu budowy (tłumaczenie). Zakłady Betonowe International, nr 4, 2016, pp 30-35.

[4] PN-EN 1015-3:2000

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INTRODUCTION TO FIRST APPROACH OF DETERMINATION OF SMALL SCALE PHYSICAL MODEL PARAMETERS OF PAVEMENT

Veronika VALASKOVA1, Jozef VLCEK2

1 Department of Structural Mechanics and Applied Mathematics, Faculty of Civil Engineering, University of Zilina, Univerzitna 8215/1, 010 26 Zilina, Slovak Republic

2Department of Geotechnics, Faculty of Civil Engineering, University of Zilina, Univerzitna 8215/1, 010 26 Zilina, Slovak Republic


Abstract. Interaction of the vehicle and the track is still an actual problem. Despite the basic simplicity of the phenomenon, the solution becomes more complex when wider range of factors need to be involved. Large portion of the local infrastructure in the Central Europe lead through the settled areas such as villages or even historical city centres as a remnant of the historical roads in past times. Local communications cannot deal with increasing traffic load which leads to the degradation of the pavement parameters and deterioration of the environment. The complexity of the phenomenon required some level of generalization without affecting the reliability of outputs. The paper presents the first approach in determination of the appropriate model scale factor and selection of the simulation materials with the testing of the key parameters. Prepared small scale physical model allows to observe the quantities such as accelerations or stresses in real time which will be helpful in numerical modelling and design of the pavement structures or remediation measures.

Keywords

Finite Element Method, pavement, simulation material, small-scale physical model.

1. Introduction

Interaction of the vehicle and the track is still an actual problem. Despite the basic simplicity of the phenomenon, the solution becomes more complex when wider range of factors need to be involved. The vehicle itself represents very complicated dynamic system and together with the mutual responses from the vehicle and the road the interaction system turns into mass of relations which is

difficult to describe by the mathematical way.

Large portion of the local infrastructure in the Central Europe lead through the settled areas such as villages or even historical city centres as remnants of the historical roads in past times. Because of absence of the higher infrastructure in some areas, large part of the traffic stays in settled areas. Local communications cannot deal with increasing traffic load which leads to the degradation of the pavement parameters and deterioration of the environment. Due to the overrun of the service life of the pavements, defects and failures occur, which leads to occurrence of stochastic sources of excitation for the dynamic system vehicle-pavement.

When dynamic behaviour of the vehicle is simplified and considering the smooth surface of the track, mathematical expression of the problem is trivial [1]. Real behaviour of the vehicle and the pavement is far more complex. On the side of the vehicle following factors influence the analysis:

• degree of generalization of the real vehicle to the model,

• non-homogeneity of the masses and their distribution in the vehicle,

• difficult estimation of the dynamic parameters of the vehicle subsystems such as stiffness, damping etc.,

• additional excitation sources from the moving vehicle part such as clutch, gearbox, other engine parts or suspension,

• change of the dynamic parameters due to the change of temperature, humidity or ageing process.

Considering the conventional asphalt or concrete pavements as a most wide-spread pavement types, the factors which have influence on the analysis can be identified as:



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• material parameters of the pavement layers and the subgrade and their inhomogeneity and imperfections,

• change of parameters in time due to the temperature, humidity, or other phenomenon such as groundwater flow or flooding,

• harmonic and stochastic unevenness of the pavement surface,

• defects and failures of the pavement such as potholes, cracks or sinkholes,

• other factors such as retarders or joints.

The pavement part of the vehicle-pavement system is often neglected in dynamic analysis and it is replaced by an elastic halfspace with basic parameters. The pavement together with the subgrade represents the important part of the dynamic interaction system vehicle-pavement. The vibrations propagate through the pavement structure and the subgrade to the environment and also affect the civil engineering structures and buildings. Additionally, when some remediation measures should be applied, mostly they are difficult applicable at the vehicles (rejection of the old vehicles from the traffic, not overloading of the trucks etc.). Because large portion of the sources of additional excitation is present in the pavements, the remediation is focused on the elimination of the source or reduction of its influence.

Undoubtedly, detailed investigation of the pavement is necessary. On the other hand, observation of its behaviour is complicated because of difficult instrumentation of observation equipment, especially in real case pavements. Considering the above mentioned statements, the complexity of the phenomenon required some level of generalization without affecting the reliability of outputs. We decided to adopt the approach of small scale modelling of the pavement with the subgrade.

2. Small scale physical modelling

Small scale physical modelling represents one of the oldest and yet still utilizable approaches to simulate and analyse the building structures. Nowadays, it is being replaced by the numerical methods but this method has still its value in some cases.

Like other simulation methods, it requires some level of generalization but this generalisation should not affect the accuracy and reliability of obtained results. Some calibration of the model is required so the behaviour of the model fits the criterion in terms of adequate values of observed quantities.

As a background for determination of the key parameters of the physical model, real scale observations of the vehicle moving on the test segment of the asphalt concrete pavement and the outputs of testing on the circular test track with various pavement compositions loaded with

the test wheel were collected. Especially real scale testing with the vehicle showed results affected by the factors mentioned above [2]. To exclude these factors from simulation, the whole vehicle was simplified into the one loading wheel as at the circular testing track [3]. The boundary conditions on the side of the vehicle can be then more clearly described and the attention can be paid to the pavement structure.

2.1. Basic parameters

Creation of the small scale physical model involves the determination of the general dimensions based on the scale of the model. This is the crucial part of the modelling because the scale restricts the possibilities of the model in terms of possible phenomenon simulation. In case of vehicle tyre – pavement interaction larger scale of model should be adopted. Rapid change in stress propagation under the contact area in particular layer cannot be described when very small scale approach is utilized. Based on the selected scale factor, the corresponded downsize of the layer thickness takes place. The selection of appropriate materials as a replacement of the real structure materials is the main challenge at the model preparation. Because of large complexity of this topic, we decided to describe the procedure of material selection and testing more precisely in this paper.

3. Material selection

Utilization of particular material should be proven by the knowledge of its behaviour under certain conditions. In this case, dynamic loading of the pavement induced variable stress state for short period of time. Thus, the materials should be selected according to the behaviour under dynamic conditions. For the first approach, a gelatine based simulation mass was utilized as a subgrade material [4]. This is possible because of smaller dynamic effect of loading on the subgrade. This material is usually used for seismic simulations of building subsoils in smaller scales [5].

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Fig. 1: Testing stand with simulation mass for pavement subgrade.

For the construction layer of selected pavement, more complex and “dynamic” approach will be applied because of higher influence of variable states of the materials.

4. Conclusion

The paper will present the first approach in determination of the appropriate model scale factor and selection of the simulation materials with the testing of the key parameters. This will be a background for the creation of the specific composition of the pavement with the asphalt concrete or cement concrete wearing course.

Prepared small scale physical model allows to observe the quantities such as accelerations or stresses in real time which will be helpful in numerical modelling and design of the pavement structures or remediation measures.

Acknowledgements

The project was performed with the financial support of the Slovak Grant National Agency VEGA 1/0006/20.

References

[1] PARK, D.-W., A. T. PAPAGIANNAKIS and I. T. KIM. Analysis of dynamic vehicle loads using vehicle pavement interaction model. KSCE Journal of Civil Engineering. 2014, vol. 18, iss. 7, pp. 2085–2092. ISSN 1976-3808. DOI: 10.1007/s12205-014-0602-3.

[2] CZERNER, M., L. S. FELLAY, M. P. SUÁREZ, P. M. FRONTINI and L. A. FASCE. Determination of elastic modulus of gelatin gels by indentation experiments. Procedia Materials Science 8. 2015, vol. 8, iss. 2013, pp. 287–296. ISSN 2211-8128. DOI: 10.1016/j.mspro.2015.04.075.

[3] VALASKOVA, V., and J. VLCEK. Experimental investigation of the vehicle-ground interaction - experiment preparation and preliminary results. Civil and Environmental Engineering. 2017. vol. 13, iss. 2/2017, pp. 99-105. ISSN 2199-6512. DOI: 10.1515/cee-2017-0013.

[4] VLCEK, J., and V. VALASKOVA. Analysis of applicability of Clegg impact soil tester for clayey soils. In: XXVII R-S-P Seminar, Theoretical Foundation of Civil Engineering. Les Ulis Cedex A: EDP Sciences, 2018, pp. 1–7. ISSN 2261-236X.

[5] SCHEIDL, M., CHIARI, M., KAITNA, M., KRAWTSCHUK, A., ZIMMERMANN T., PROSKE, D. Analysing debris-flow impact models, based on a small scale modelling approach. Surv Geophys. 2013. pp 121-140. ISSN 0169-3298. DOI: 10.1007/s10712-012-9199-6.

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INFLUENCE OF NUMERICAL DIFFUSION ON CFD SIMULATION PRECISION OF VELOCITY AND TEMPERATURE FIELD

Vladimíra MICHALCOVÁ1, Kamila KOTRASOVÁ2

1Department of Structural Mechanics, Faculty of Civil Engineering, VSB - Technical University of Ostrava, Ludvíka Podéště 1875/17, 708 33 Ostrava-Poruba, Czech Republic

2Institute of Structural Engineering, Faculty of Civil Engineering, The Technical University of Kosice,

Vysokoškolská 4, 042 00 Kosice, Slovak Republic


Abstract. Numerical diffusion impairs the accuracy of discrete solutions of the equations governing the convective transport of a scalar when the flow is not aligned with grid lines. Numerical diffusion leads to unintentional smoothing of advected gradients. This work presents an assessment of numerical diffusion in CFD code Ansys Fluent 2019 R1 and available means of reducing impairment.

Keywords

CFD, discretization scheme, numerical diffusion, transport equation.

1. Introduction

The solution of transport equations in Fluent uses a discretization process in which the basic problem is the exact calculation of the transport quantity across the walls of a specific volume and its convective flow across It is necessary to expect with the so-called "false" numerical diffusion and also the occurrence of values that are outside the range of the correct solution. This work compares the physical accuracy of the calculation using the offered discretization calculation schemes designed in the CFD code and the possibilities how to reduce these numerical errors.

Fluent uses the finite volume method to convert general transport equations into a system of linear equations that are solved numerically by the Gauss-Seidel iteration method. This method involves by the integrating of equations in each control volume-cell, the result are the discrete equations that present the flow equilibrium, i.e. the laws of preserving each transport variable in the given volume. In this work, the discretization of equations is

shown on the conservation law of the transport variable Φ in stationary flow, which presents the equilibrium flow in constant volume.

Numerical diffusion arises mainly when the flow direction is not parallel to the grid walls. However, such optimum conditions (parallel flow) can only be achieved when calculating straight pipe sections without obstacles using hex cells. The current direction is always in the general direction with respect to the cell walls (hexahedral, tetrahedral, polyhedral) in vast majority of flow cases and it is necessary to count with a numerical error by evaluating the convective state.

2. Evaluated parameters

The aim of this work is to evaluate the physical accuracy of numerical computing in depending of various parameters. The object of the research is determining of the dispersion of numerical diffusion of the monitored quantity that are outside the range of specified boundary conditions. The monitored factors that have influence on the quality of the computing are in next subsections.

2.1. Mesh parameters

Influence of mesh density (grid) and typology mesh are evaluated.

2.2. Discretization scheme

Fluent stores discrete scalar values in the cell centre. In equations, however, scalar quantities are also required on the cell walls to calculate the convective term. These are determined by interpolation from the values in the centres of adjacent surrounding cells. This process uses a discretization "upwind" scheme, which means that the



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value is derived from the value of the next cell downstream. Fluent allows you to choose from five upwind schemes for calculating the convective term. The accuracy of the calculation of these schemes is tested.

2.3. Gradient variables

When solving the flow, it is also necessary to determine the gradients that are necessary for calculating the scalar values on the cell walls, but also for the discrediting of the convective and diffuse elements. In Fluent, the gradient can be calculated in three ways: Green-Gauss Cell-Based, Green-Gauss Node-Based and Least Squares Cell-Based. All three methods are also tested.

3. Numerical experiment

The 3D stationary flow of computational domain of virtual gas with dimension 1 x 1 x 0.25 m is simulated, the gas density is ρ = 1 kgm-3, see Figs. 1 and 2. The values of thermal conductivity λ [Wm-1 K-1] and dynamic viscosity μ [Pa.s] of gas are close to zero.

Fig. 1: Three mesh typologies (hexahedral, tetrahedral, polyhedral).

Fig. 2: Two different densities of tetrahedral mesh.

The boundary conditions are setting so, that the identical vectors are entering at two mutually perpendicular walls with speed vx and vy. One of these walls has the temperature T1 = 300 K and second T2 = 400 K. The output on the two opposite walls is zero flow of all quantities across the border (normal speed is zero). The numerical diffusion (dispersion) of the transport variable (temperature) is in Fig. 3.

Fig. 3: Numerical difusion, sparse mesh hexahedral and tetrahedral.

The number of cells on the side walls of a region in which the value of the transposition variable is higher than based on boundary conditions, that is, the cell where the temperature is higher than 400 K, is in Fig. 4. It is the computing using the dense tetrahedral mesh of computational domain with different discretization scheme.

Fig. 4: Cells with a values of transport variable above the allowed range, tetrahedral cells, Second-order upwind (left), Third-order upwind (right).

The influence of all factors on the values of the transport variable outside the range of input parameters is documented in Fig. 5.

Fig. 5: The influence of all factors on transport variable values outside the range of input parameters.

4. Conclusion

It is examined, that the all watched factors have influence on computation quality. It will be elaborated in full paper how are the dominant effects and influence of the different combination effects of computation parameter setting.

Acknowledgements

In The paper has been supported by the project of “Conceptual development of science and research activities 2020” on the Faculty of Civil Engineering, VŠB – TU Ostrava and by the Ministry of Education, Youth and Sports from the Large Infrastructures for Research, Experimental Development and Innovations project „IT4Innovations National Supercomputing Center – LM2015070“ and by the Scientific Grant Agency of the Ministry of Education of Slovak Republic and the Slovak Academy of Sciences the project VEGA 1/0374/19.

3,64

0,16

3,63

0,67

0,11 0,12 0,25 0,25

2,78

0,66

3,43

0,86

2,86

4,77

1,7

5,08

1,53

0,36

2,07

2,79

8,23

6,376,69

4,32

0

1

2

3

4

5

6

7

8

9

10Transport variable values outside the rang of input parameters

lower variance of transport value valuesupper variance of transport value valuestotal variance of transport value values

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SENSITIVITY OF FACTORS INFLUENCING DYNAMIC MODULUS OF ASPHALT CONCRETE

Hai Viet VO1

1Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City, Viet Nam

[email protected]

Abstract. The sensitivity analysis of factors that influence the dynamic modulus of dense asphalt concrete in Viet Nam was presented in this paper according to some predictive models of dynamic modulus by applying Monte Carlo simulation method. The predicted values were compared with the actual tested data. The degree of affection of the factors was determined based on the prediction results of dynamic modulus. It was found that all tested samples show good agreement between the measured and predicted data. As a result, quality control would be improved to ensure quality of work to be done on site from asphalt hot mix design state to construction.

Keywords

Complex shear modulus, phase angle, sensitivity analysis, dynamic modulus.

1. Introduction

The failure of pavements is mainly caused by the combined effects of the repeatable load and the constant change of weather. Therefore, the study of thermomechanical properties of asphalt concrete is essential to improve the methods and components to create types of asphalt with better resistance to the above-mentioned impacts. In addition to the methods of controlling the selection of suitable aggregate and binders, or optimizing aggregate gradation used in asphalt mixtures [1], at present, the research direction is the relationship between the mechanical properties of asphalt concrete and asphalt binder. The complex shear module, G* and phase angle, δ of asphalt are two of the most important factors in the US-based classification system. In addition, G* and δ are two important inputs used to predict dynamic modulus values of asphalt concrete in Witczack model, modified Witczack model, and Hirsh model [2]. Dynamic modulus of dense Asphalt Concrete, E* is one of the most important input parameters used for designing and evaluating

pavement structure according to the mechanical-empirical pavement design guide [3]. Because of its importance, there has been a lot of research on predictive models of E* as well as sensitivity analysis of input parameters that influence dynamic modulus in order to find out which one is the most influence on E* [4]. However, the degree of affection of these input parameters on the value of E* is quite different from one to another.

This paper is to evaluate the sensitivity of factors that influence E* was performed to compare the effects of type of asphalt to other factors. Monte Carlo simulation was applied to perform the sensitivity analysis. Witczak Model, Modified Witczak Model, and Hirsch Model were applied to predict E*, the degree of affection of the factors was then determined.

2. Materials and Methods

2.1. Materials

Values of dynamic modulus depends on a lot of parameters, include: Nominal maximum aggregate size, Dmax, type of bitumen the key property of which is complex shear modulus G* or dynamic viscosity of bitumen, passing percent No.200 (0.075mm), cumulative retaining percent on the sieve sizes No.4, No.3/8 and No.3/4 (4.75mm, 9.5mm, 19mm), volumetric properties (Va, VFA and VMA). The 60/70 bitumen, which is the most common in Viet Nam, was used in this study. The rheological properties of the bitumen are summarized in Tab. 1. Tab. 1: Rheological properties of the bitumen.

Bitumen 60/70 Standard

Penetration, at 25oC

(0.1mm) 62 60-70

Softening point, Ring and ball method

(oC) 49.1 46

Ductility, at 25oC, 5cm/min (cm) >100 100

Gb 1.024 - Elasticity, at 25oC, 10cm

(%) - 70


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Empirical research was at the Project in Hai Phong in December 2017. Input parameters using for sensitivity analysis of the Witczak models and Hirsch model were collected from data of asphalt mixture design AC12.5 with Dmax of 12.5, designed by Marshall method [5]. The aggregate grading and properties of AC12.5 met the requirements of Decision No.858 [6]. The aggregate grading and rheological properties of AC12.5 are given in Tab. 2 and Tab. 3, respectively. Tab. 2: Aggregate gradation of AC12.5.

Sieve size

(mm) Combined grading

(% passing) Decision No. 858

Min Max

19 100 100 100

12.5 79 74 90

9.5 68.1 60 80

4.75 40.2 34 62

2.36 24.1 20 48

1.18 17.0 13 36

0.6 10.9 9 26

0.3 8.2 7 18

0.15 6.5 5 14

0.075 4.7 4 8

Tab. 3: Rheological properties of AC12.5.

Parameters Value Requirements

Pb (%) 4.27 - Va (%) 5.1/(5.91) 3÷6

VMA (%) 14.75/(15.424) >=13.5

VFA (%) 66.02/(61.698) 65÷75

S (kN) 14.62 >=8

Flow (mm) 3.07 1.5÷4

Gmm 2.556 - Gsb 2.727 - Gb 1.024 - Gmb 2.428/(2.405) -

2.2. Sensitivity analysis

Sensitivity analysis is a technique to evaluate influence between input parameters and output results of a predicting model [7,8]. In a global sensitivity analysis, all input parameters are varied simultaneously from their base cases and interactions among input parameters are considered. The global sensitivity analysis will evaluate which input parameter is the most influence on the output response of a model and it is more proper than Once-At-a Time method [8]. Global sensitivity analysis requires the Monte Carlo simulation which can be run by Oracle Crystal Ball software [9] to carry out sensitivity analysis of input parameters for the dynamic modulus predictive models. This software can be integrated into MS Excel to perform calculation in the global sensitivity analysis. Monte Carlo simulation is a method of using random numbers or

random variables received based on deterministic random numbers [10]. When randomly assigning input parameters to the predetermined distribution law, then the set of output random parameters with their distribution rule is determined. Today, simulation data are often used in the cases that resources are restricted or collecting data is costly or impractical.

3. Results and discussions

The dynamic modulus can be determined by experiment or

prediction depending on the level of pavement structure

design according to the mechanical-empirical method. E*

was estimated based on some properties of asphalt and

asphalt mixture. The models, Original Witczak Model,

Modified Witczak Model, and Hirsch Model [2,4] were

applied for the prediction of E*.

In this paper, the distribution types of the input parameters (Va, Vbeff, VMA, VFA, P200; P4; P3/8; P3/4) were determined based on a database collected from actual production and construction of asphalt mixes at Hai Phong Urban Transport Development Project of the hot mix asphalt for a surface course. For dynamic modulus, viscosity and phase angle of asphalt (G*, η, δ). Types of distribution are determined based on concerned data in the test of complex shear modulus of the 60/70 asphalt at IFSTTAR as mentioned above. Type of distribution of frequency influencing E* is determined based on frequency data used for carrying out the test of E* at the building material laboratory of University of Transport and Communications, Vietnam. The Oracle Crystal Ball software was applied with the number of trial runs of 3000, confidence level of 95%.

(a)

(b)

84,4%

15,2%

-0,2%

-0,1%

0,0%

0,0%

0,0%

-100,0% -50,0% 0,0% 50,0% 100,0%

ηf

P4

Va

P200

P3/8

Vbeff

Sensitivity: log(E*)

97,8%

-2,1%

-0,1%

-0,1%

0,0%

0,0%

0,0%

-100,0% -50,0% 0,0% 50,0% 100,0%

G*

Delta

Va

P200

P3/8

Vbeff

P4

Sensitivity: log(E*)

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(c) Fig. 1: Sensitivity of E* by a) Original Witczak Model, b) Modified Witczak Model, and c) Hirsch Model.

As seen in Fig. 1, type of asphalt, G*, , and δ has the greatest influence on the dynamic modulus of asphalt concrete, the second one is loading frequency, f in the original Witczak Model, and then volumetric properties together with values of P200, P4; P3/8; P3/4 of the Witczak Models and Hirsch Model. Coefficients concerning the volumetric properties of asphalt mixture are smaller than coefficients of G*, , δ, and f, which are the properties of asphalt. Therefore, proper selection type of asphalt and the optimum asphalt content for asphalt mixture design is very important to improve the quality of asphalt pavement.

In order to evaluate feasibility of application of the above predictive models for prediction of E* for asphalt hot mixes in Viet Nam. Samples were taken on site at a specific section and tested to determine E* and other characteristic of asphalt mixes. The testing of E* was carried out by CRT-UTM-NU Testing Machine, testing procedures comply with AASHTO TP 62-07. The frequencies used for testing E* are 0.1 Hz, 0.5 Hz, 1 Hz, 5Hz, 10Hz, and 25Hz. Temperature range is 10oC, 30oC, 50oC with angular frequency of 10 rad/s or a loading time on the surface course about 0.1s [11,12]. Each temperature will be combined with the 6 frequencies above. Based on the test results, a master curve of dynamic modulus of asphalt mixes is constructed. For purpose of preliminary evaluation, only the values of dynamic modulus at 10 Hz are compared with predictive values of three above predictive models. As seen in Table 8, sensitivity analysis and predictive E* results for the above models are for reference only. Because database uses for sensitivity analysis and prediction of dynamic modulus according to the above models collected at only one local areas with one type of bitumen only and for asphalt concrete surface course only. In a previous study [13], it is concluded that the Hirsch model is simpler and more rational for predicting modulus and predicted moduli were potentially closed to actual modulus values. The Hirsh model, in this study, has more accurate predicted values, and more accurate at lower temperature. Tab. 4: The difference of E* between actual test results and predictive values.

T

(oC) Actual values

Original Witczak Model

Modified Witczak Model

Hirsh

Model

10 7863.29 69.49 193.95 15.11

30 2649.87 73.58 75.19 33.53

50 649.08 71.82 33.80 48.54

4. Conclusion

This paper is to evaluate the complex shear modulus and phase angle of the asphalt in Viet Nam and their effects on the dynamic modulus of asphalt concrete mixtures. The dynamic modulus of asphalt concrete depends on many input parameters, however, type of asphalt (G*, δ, and ) have the greatest influence, next one is the asphalt mixture design work with the selection of combined aggregate grading and optimum asphalt content that are expressed through value of air void. As the authors’ consideration, it is necessary to have more experiment database to calibrate and adjust coefficients of the predictive models to ensure that they can be applied for asphalt mixes in Viet Nam.

References

[1] NCHRP 673. A manual for design of hot mix asphalt with commentary, Transportation Research Board, Washington D.C. 2011.

[2] GARCIA, G. and M. THOMPSON. HMA Dynamic Modulus Predictive Models – a review. Report No. FHWA-ICT-07-005, 2007, pp. 8-25. ISSN 0197-9191.

[3] NCHRP 1-37A. Mechanistic-empirical pavement design guide of new and rehabilitated pavement structures (MEPDG), Transportation Research Board, Washington D.C. 2004.

[4] KIM, R.Y., B. UNDERWOOD, M.S. FAR, N. JACKSON and J. PUCCINELLI. LTPP Computed Parameter: Dynamic Modulus, Report No. FHWA-HRT-10-035. 2011, pp. 5-12.

[5] AASHTO T315-12. Standard Method of Test for determination the Rheological Properties of Asphalt Binder Using a Dynamic Shear Rheometer. American Association of State Highway and Transportation Officials, Washington D.C. 2012.

[6] DECISION NO.858. Application guideline of current standards to fortify quality control of asphalt mixture design and flexible pavement construction for the road with high volume traffic. Ministry of Transport, Hanoi, Viet Nam, 2014. (in Vietnamese).

[7] SALTELLI, A., S. TARANTOLA and F. CAMPOLOGO. Sensitivity Analysis as an Ingredient of Model. Statistical Science. 2000, vol. 15, iss. 4, pp. 377-395. DOI

[8] LI, R. Sensitivity Evaluation of Mechanical-Empirical Pavement Design Guide (MEPDG) for Flexible Pavement Performance Prediction, Doctoral Dissertation, University of Maryland, College Park, MD. 2013, pp. 8-16, 40-56.

[9] ORACLE CRYSTAL BALL [computer software]. Oracle, Santa Clara, California.

99,9%

0,1%

0,0%

-100,0% -50,0% 0,0% 50,0% 100,0%

G*

VFA

VMA

Sensitivity: E*

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[10] CODDINGTON, P.D. Analysis of random number generators using Monte Carlo simulation. International Journal of Modern Physics C. 1994, vol. 5, iss. 3, pp. 547-560. ISSN 0129-1831. DOI: 10.1142/S0129183194000726.

[11] AASHTO T315-12. Standard Method of Test for determination the Rheological Properties of Asphalt Binder Using a Dynamic Shear Rheometer. American Association of State Highway and Transportation Officials, Washington D.C. 2012.

[12] HUNTER, R.N., A. SEFT and D. READ. The Shell bitumen handbook, 6th Edition, ICE Publishing, Westminster, London. 2015, pp. 139-141.

[13] CHRISTENSEN, D.W., T.K PELLINEN, and R.F. BONAQUIST. Hirsch Model for Estimating the Modulus of Asphalt Concrete, Journal of the Association of Asphalt Paving Technologists. 2013, vol. 72, pp. 97-121. ISSN 02702932.

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DURABILITY AND RELIABILITY OF THE WEATHERING STEEL INFLUENCED BY CHLORIDES

Monika KUBZOVA1, Vit KRIVY1

1Department of Building Structures, Faculty of Civil Engineering, VSB – Technical University of Ostrava, Ludvika Podeste 1875/17, Ostrava-Poruba, Czech Republic


Abstract. Bridge structures should be designed and maintained using such procedures that secure reliable functioning over their entire planned lifetime. Insufficient maintenance of bridges together with their inappropriate design can adversely affect the durability and reliability. Durability of the structure is considerably affected by the microclimate around the bridge. The basic parameters of the local environment are relative humidity, temperature, dust, and corrosion stimulators (chlorides and sulphur dioxide). Measurements of the key parameters of the environment surrounding the bridge is very important. These measurements can help the bridge administration in choosing the appropriate maintenance or repair methods. In this article there is shown relationship between the measured amount of spread chlorides on the surface of the bridge structure and the basic characteristics of corrosion layers (thickness of corrosion layer, corrosion losses). The article also compares standard methods of measuring the deposition rate of chlorides. There are also shown experimental measured deposition rates of chlorides influenced by changing distances from their source.

Keywords

Corrosion layer, deposition rate of chlorides, weathering steel, bridge.

1. Introduction

Bridges are a key element of transport infrastructure. Around 20 % of road bridges in the Czech Republic are therefore in unsatisfactory condition due to corrosion damage [1, 2]. The most typical reasons for the formation of corrosion damage are being:

• Inappropriate design of bridge´s details.

• Leakage from the damaged bridge’s drainage

system.

• Improperly designed methods of protection against corrosion.

• Insufficient bridge maintenance.

A specific group of bridges used without any protection against corrosion are bridges designed form weathering steel [3]. In the Czech Republic, several important road bridges have been constructed with weathering steel. Local corrosion defects caused by adverse microclimatic conditions in the bridge’s environment were identified in a few bridges. Impurities and chlorides had been deposited on the bottom flanges of the main girder. Deposition of chlorides and development of corrosion layer are monitored on the surface of selected weathering steel bridges in Ostrava by experimental measurements.

2. Material and methods

The chloride deposition rate is measured by two basic methods – wet candle method and dry plate method in horizontal and vertical position in accordance with [4]. For monitoring of development of corrosion layers on the surface of the steel are used corrosion samples from S355J2WP in accordance with [4].

Fig. 1: Selected methods for experimental testing.



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The basic difference between selected two bridges located on the same road is that bridge B1 is above the highway (there is expected higher amount of chlorides spreads to surfaces of bridge) and the bridge B2 is above the railway. Corrosion samples and devices for monitoring chloride deposition rate were located on selected positions (Table 1).

Tab. 1: Description of selected surfaces for experimental bridges.

bridge ID description of surfaces

B1

S1 external girder, north orientation, in the direction of transport

under the bridge

S2 internal girder, north orientation, in the direction of transport

under the bridge

S3 internal girder, south orientation, opposite the direction of

transport under the bridge

S4 external girder, south orientation, opposite the direction of

transport under the bridge

B2 S5 external girder, north orientation

S6 internal girder, north orientation

3. Results

The deposition of chlorides was continuously measured from December 2016 to December 2018. The annual average values of the chloride deposition rate for each year, method and position are shown in Figure 2 (where C is wet candle method, PH is dry plate method in horizontal position and PV is dry plate method in vertical position).

Fig. 2: Annual average chloride deposition rate [mg/(m2.d)/y].

The thickness of corrosion layer tcorr was measured after one year of exposure by magnetic-induction method. Results corresponding to exposure in 2017 and 2018 are shown in Figure 3.

Fig. 3: Thickness of corrosion layer tcorr [μm/y] after one year of exposure.

4. Conclusion

The relationship between the annual corrosion layer thickness and the annual average deposition rate measured using the horizontally (PH) and vertically (PV) oriented dry plate materials, and the respective thickness of the corrosion layer is shown in Figure 5.

Fig. 4: Relationship between the annual average chloride deposition rate and the corrosion layer thickness tcorr after one year of exposure.

Acknowledgements

This article was accomplished with the financial support of the Grant Agency of the Czech Republic (Project Registration Number 18-07949S).

References

[1] ABDUL – WAHAB, S. A. Effect of air pollution on atmospheric corrosion of engineering metals, Practice Periodical of Hazardous, Toxic, and Radioactive Waste Management, 8(4), 2004.

[2] ALCÁNTARA, J., CHICO, B., DIÁZ I., FUENTE, D., MORCILLO, M. Airbone chloride deposit and its effect on marine atmospheric corrosion of mild steel, Corrosion Science, 97, 2015.

[3] MCCONELL, J. R., SHENTON, H. W., MERTZ, D. R. National review on use and performance of uncoated weathering steel highway bridges, Journal of Bridge Engineering, 19(5), 2014.

[4] KRIVY, V., KUBZOVA, M., KONECNY, P., KREISLOVA, K. Corrosion Processes on Weathering Steel Bridges Influenced by Deposition of De-Icing Salts. Materials, 12(7), 2019.

0

5

10

15

20

S1

-C

S1

-PH

S1

-PV

S2

-C

S2

-PH

S2

-PV

S3

-C

S3

-PH

S3

-PV

S4

-C

S4

-PH

S4

-PV

S5

-C

S5

-PH

S5

-PV

S6

-C

S6

-PH

S6

-PV

2018

2017

0

50

100

150

200

250

S1

- V

S1

- H

S2

- V

S2

- H

S3

- V

S3

- H

S4

- V

S4

- H

S5

- V

S5

- H

S6

- V

S6

- H

2018

2017

y = 26.33e0.1907x

R² = 0.5827

0

25

50

75

100

125

150

175

200

225

0 1 2 3 4 5 6 7 8 9 10 11 12

Th

ick

nes

s of

corr

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/y]

Chloride deposition rate [mg/(m2.d)/y]

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DIFFERENT APPROACHES TO RECYCLE WASTES FOR CONSTRUCTION MATERIAL PRODUCTION

Quoc-Bao BUI1,*, Hoai Bao LE1,2, Thanh-Phong NGO1,3, Duc-Hien LE1, Minh-Tung TRAN1, To-Anh-Vu PHAN1

1 Sustainable Developments in Civil Engineering Research Group, Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam

2 Mien Tay Construction University, Vinh Long, Vietnam 3 Van Lang University, Ho Chi Minh City, Vietnam

*corresponding author: [email protected]

Abstract. This paper presents different approaches to valorise different inert wastes for the manufacturing of construction materials. The first case is to recycle low-quality fly ash and bottom ash from the thermal power plants (TPP) which cannot be used for cement or concrete industry. The fly ash substituted partially the cement and the bottom ash substituted partially the sand, to manufacture the cement concrete. The second case is similar to the first one, but the cement was replaced by an alkali-activated binder. The third case is the recycling aggregates from construction demolitions, and using the alkali-activated binder manufacture recycled concretes. The last case is the valorisation of excavated soils for the manufacturing of bricks, with alkali-activated binder. The results showed that recycling a maximum of construction and industrial wastes was possible, the recycled materials can be applied for structural or non-structural materials.

Keywords

Alkali-activated concrete, fly ash, bottom ash, soil-based material, recycled aggregate concrete.

1. Introduction

Since several years, there have been more and more Thermal Power Plants (TPP) constructed in Vietnam which work with coal. These TPP generate very important quantities of wastes (bottom ash and fly ash): about 15 Mtons every year (75% fly ash + 25% bottom ash) which create serious environmental problems in Vietnam [1]. For example, in 2016, 23 Mtons of fly and bottom ashes have been accumulated and it is forecasted that in 2030, 61 Mtons will be accumulated. There will not be enough spaces on TPP sites to stock the ashes. In fact, in developed countries, fly ash (FA) is a by-product which can be used for the cement/concrete industry, however, the most of TPP

in Vietnam does not include the phase which separates the FA from the bottom ash, therefore the FA from the most of TPP does not have satisfying quality to be used in cement industry or for concrete production. The post-treatment to separate the FA is expensive, so the FA and bottom ash purely become wastes (Fig. 1:). The valorisation of these ashes is a challenge.

Fig. 1: Fly ash and bottom ash stocked on a TPP site. Source: Vietnamese Ministry of Constructions.

In the other hand, there is a strong willingness from the Vietnamese government to replace clayed burnt bricks (which is looked as environmental-unfriendly due to its consumption of energy and agriculture soils during the manufacturing) by greener materials. The unburnt bricks are often proposed but there are several difficulties related to the economic, traditional and environmental aspects because the current unburnt bricks possess high cement amounts (~ 25% by weight), which increases the cost and the carbon footprint.

Another problem is that following several studies (for example [2]), among different types of inert wastes from the construction industry, about 10% is concrete, but about 55% is unpolluted stones and soils. However, the excavated soil is generally not recycled to produce construction materials. So, the valorisation of excavated soils for the material production is an interesting topic to be explored [3].

From the three above problems, different strategies have


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been proposed and investigated in this paper:

• Using low-quality FA and bottom ashes for construction materials

• Using recycled aggregates for concretes

• Using local soils for construction material production

The idea of this study is that if the materials obtained have low strength, they can be used for infill elements (bricks), if they have high strength, they can be used for structural elements (concrete). Another aim of this study is to reduce the cement amount, or replacement totally the cement by another binder.

2. Different techniques investigated

The first family of techniques proposed is to use cement as binder and propose the concretes incorporating low-quality ashes. Three cases were investigated: Cement substituted partially by fly ash; Sand substituted partially by bottom ash; Cement and sand substituted partially by fly and bottom ashes.

The second family do not use any cement and replace it by alkali-activated binder which has been shown more sustainable than cement [4]. Three cases were also investigated: Alkali-activated concrete with low-quality fly ashes; Alkali-activated bricks with low-quality fly ashes; Alkali-activated concrete with good-quality fly ashes and recycled coarse aggregates.

2.1. Approach 1: Cement concrete with low quality ashes

The low-quality fly ash (FA) and bottom ash were taken at a TPP in the centre of Vietnam (Fig. 2:). The ashes were analysis the chemical composition following American Standard ASTM (2015) which showed high carbon contents (about 10%) for both ashes. The fly ash is classified C-class following ASTM.

Fig. 2: Low-quality fly ash used in the present study.

A reference cement concrete was also manufactured with a mean compressive strength of 30MPa, which is a current grade. The slump demanded was 7 ±1cm. The classical Dreux-Gorisse proportioning method was applied to determine composition of the reference concrete. The composition obtained was of Gravel:Sand:Cement:Water=42%:28%:20%:10% (in mass), respectively.

Then, the cement (20% in mass) in the reference case is substituted by fly ash, with respectively three cases:

• 7% cement + 14% FA;

• 7% cement + 28% FA;

• 7% cement + 28% FA + 14% Bottom Ash;

The cubic specimens (15x15x15) cm3 were manufactured (three specimens for one mean result). The corrector factor was applied to obtain the compressive strength on cylindrical specimens.

2.2. Approach 2: Alkali-activated concrete using low-quality fly ash

The fly ash contents alumino-silicate, by using an activator (NaOH, Na2SiO3, Fig. 3:), one can create the geopolymer binder which can totally replace cement.

Fig. 3: Activator to manufacture alkaline-activated concrete.

A parametric study was carried out and confirmed the ratio recommended in the literature: Na2SiO3 / NaOH = 2.5 [5]. In this case the alkaline-activated binder replaces totally the cement in the previous case (20% in mass), that was why the composition chosen was: 14%FA + 2%NaOH + 5%Na2SiO3. It should be noted that the ratio fly ash / alkaline-activated solution (Na2SiO3 + NaOH) = 2 is also a current ratio recommended in several studies, and was also verified by a parametric study. It is worth noting that the slump demanded for alkali-activated concrete is higher than cement concrete, and a minimum value of 20 cm is needed for a correct workability. The specimens were cured in the laboratory ambient conditions (25°C, 60 RH).

A second reference concrete was manufactured which was an alkaline-activated concrete with the same composition, but by using the F-class fly ash (good quality).

2.3. Approach 3: Alkali-activated concrete with recycled coarse aggregate

In this approach, the composition of concrete is similar to the above approach, but the coarse aggregate was 100% recycled from a real building demolition. The F-class fly ash was used to limit the number of variables. Two modes of curing were investigated: the first was in ambient conditions (25 °C), for the second, the specimens were placed at 60 °C in oven for 24h of the first day. Two cases were also investigated: with and without superplasticizer. It is worth noting that this approach is only recently explored by few studies in the literature.

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2.4. Approach 4: Valorisation of in-situ soils

In function of the soil type, different techniques of soil-based (or earth) materials can be applied: Soil concrete, Rammed earth, Adobes, Compressed earth blocks, Cob [6]. In the framework of the present study, a sandy-soil was used which was taken from the excavated soil of a construction site. The technique proposed was alkali-activated adobes. The composition of alkali-activated solution was the same as the previous approach, but in this case, only the soil was used, there was no gravels or sand. The adobe was obtained with the manual compression in a wooden formwork (Fig. 4:).

Fig. 4: An alkali-activated adobe obtained.

Two modes of curing were investigated: in ambient conditions (25 °C); at 90 °C in oven for the first 24h.

3. Results

3.1. Approach 1: Cement concrete with low quality ashes

The results obtained on the cement concretes with low quality fly ash and bottom ash are illustrated in Fig. 5:, which shows that the substitution by fly ash or/and bottom ash reduced the compressive strength. However, the results are acceptable for low strength concrete (about 15-20 MPa of compressive strength at 28 days).

Fig. 5: Compressive strength in function of time.

3.2. Approach 2: Alkali-activated concrete using low-quality FA

First, the referent alkali-activated concrete with F-class FA had 34 MPa of compressive strength at 28 days (for the

ambient curing) and 40 MPa (for the curing at 60°C). The results obtained on the alkali-activated concretes using low-quality FA are illustrated in Fig. 6:. It is observed that the alkali-activated concrete had lower compressive strengths than that of cement concrete. This result is only acceptable for non-structural materials (such as bricks).

Fig. 6: Compressive strength in function of time.

3.3. Approach 3: Alkali-activated concrete with recycled coarse aggregate

The results of compressive strength obtained on the alkali-activated concretes with recycled coarse aggregate: First, it is observed that with the 60°C curing, the compressive strength increases 25-30% compared to 25°C curing. Then, the compressive strength evaluated from 15-25MPa (at 3 days) to 25-35 MPa (at 28 days), respectively for the cases of curing under ambient conditions and with 60°C curing during 24h. However, no clear effect of superplasticizer was observed.

3.4. Approach 4: Valorisation of in-situ soils

The dry density obtained for the adobes was 1.86 ± 0.02. The mean compressive strength at 28 days was 25 ±4 MPa. These results were a surprise because it was very high for current alkali-activated bricks (about 1-6 MPa [7]). The water absorption tested was 5.2%. It was observed that for specimens cured at 90°C (for 24h), the compressive strength increases 30% compared to the ambient cured specimens. So the adobes obtained satisfy the criteria following ASTM about water absorption and the compressive strength for load-bearing bricks (for both cement brick and clay burnt bricks, because to our knowledge, there is not yet the standard for alkali-activated adobes). So, an optimization should be interesting to reduce the binder amount, to have a more sustainable material.

4. Conclusion

The present paper illustrates different approaches to valorize the industrial waste for the manufacture of

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construction materials. The paper shows that recycling a maximum of construction and industrial wastes is possible: from concrete waste, soil waste and fly/ bottom ashes (low quality). The recycled materials can be applied for structural or non-structural materials.

The alkali-activated materials are a promising alternative approach to replace cement. However, the detailed Life Cycle Assessment studies to assess the sustainability of each approach will be interesting. The optimization of the formulation on the economic point of view will also necessary.

Acknowledgements

This project that has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under grant agreement no. 777823.

References

[1] VMOC, Vietnamese Ministry of Constructions (2017)

[2] SOES, Commissariat Général au Développement Durable, Bilan 2014 de la production de déchets en France, CGDD SOeS- Data-Lab, 2017.

[3] BUI Q.B., MOREL J.C., TRAN V.H., HANS S. and OGGERO M., How to use in-situ soils as building materials, Procedia Engineering 2016, 145, pp. 1119 – 1126.

[4] HABERT G., OUELLET-PLAMONDON C., Recent update on the environmental impact of geopolymers, RILEM Technical Letters 2016, 1, pp. 17 – 23.

[5] BOUAISSI A., LI L.Y., ABDULLAH M.M., BUI Q.B., Mechanical properties and microstructure analysis of FA-GGBS-HMNS based geopolymer concrete, Construction & Building Materials 210 (2019) 198–209.

[6] BUI Q.B., MOREL J.C., HANS S., MEUNIER N. Compression behaviour of nonindustrial materials in civil engineering by three scale experiments: the case of rammed earth, Materials and Structures, (2009) vol. 42, N° 8: 1101-1116

[7] MIRANDA T., SILVA R.A., OLIVEIRA D.V., LEITÃO D., CRISTELO N., OLIVEIRA J., SOARES E., ICEBs stabilised with alkali-activated fly ash as a renewed approach for green building: Exploitation of the masonry mechanical performance, Construction and Building Materials 155 (2017) 65–78.

CUTE 2020 PAPER: 22


RESPONSE OF LIGHTWEIGHT RUBBERIZED CONCRETE UNDER

IMPACT LOAD

Tung M. TRAN1, Thong M. PHAM2

1Sustainable Developments in Civil Engineering Research Group, Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City, Viet Nam

2Center for Infrastructural Monitoring and Protection, School of Civil and Mechanical Engineering, Curtin University,

Kent Street, Bentley, WA 6102, Australia

[email protected]

Abstract. This paper presents results of an experimental study on the behaviour of concrete made of waste car tyres aggregates with the rubber content of 0%, 15%, and 30% under impact load. The dynamic compressive characteristic of the rubberized concrete was tested using a Split Hopkinson Pressure Bar equipment. The experimental results have shown excellent impact resistance of rubberized concrete as compared to that of normal concrete because it eliminated the crack propagation and provided progressive failures as compared to normal concrete. The experimental results also showed that the compressive strength and axial strain at maximum dynamics tress of rubberized concrete are sensitive to the strain rate which depends mostly on the rubber content.

Keywords

Impact resistance, rubberized concrete, dynamic behaviour.

1. Introduction

Waste rubber tyre has been considering as a crucial environment issue for the last 30 years. Many efforts have been made to reduce effect of waste rubber tyre on the environment and the use of Rubber crumbs which are made from waste rubber tyre to replace aggregate in producing concrete has been showing to be one of the potential solution [1-6]. Compared to normal concrete rubberized concrete has relatively lower compressive strength but higher energy absorption, especially the rubberized concrete with high rubber content [3, 7]. This property help promoting many researches of scientists around the world for the application rubberized concrete.

Basically, rubberized concrete has identical ingredients as

normal concrete excluding the partly replacement of rubber crumbs for the normal aggregate. With the presence of rubber crumbs, rubberized concrete become softer and has properties somehow like rubber. Therefore, its mechanical properties are different from normal concrete. Currently, the behaviour of rubberized concrete under quasi-static load has been well examined [1]. However, the study on the behaviour of rubberized concrete under impact load which can help improving the application of rubberized concrete is very limited. Therefore, in this study the dynamic properties of rubberized concrete are experimentally examined. A total of 33 concrete specimens with the rubber crumbs- aggregate replacement percentage by volume of 0%, 15% and 30% were prepared. The prepared specimens were tested by both quasi-static and impact loads and results of these tests are presented.

2. Experimental program

Three rubberized concrete mixes with three rubber crumbs- aggregate replacement of 0%, 15% and 30%. The ingredient of these concrete mixes is shown in Tab. 1 and the physical properties of crumbs rubber are shown Tab. 2. A total of 33 specimens were cast in which 9 specimens with a diameter of 100 mm and a length of 200 mm were used for the quasi-static compressive tests and 24 specimens with a diameter of 100 mm and a length of 50 mm were used for Split Hopkinson Pressure Bar compressive tests. The quasi-static compressive tests and Split Hopkinson Pressure Bar compressive tests were carried out on MATEST and SHPB systems as shown in Fig. 1. Tab. 1: Proportion of concrete mixes (kg/m3).

Rubber crumbs replacement Cement Water Aggregate Sand

Rubber crumbs

0% 426 205 880 843 0

15% 426 205 748 717 45

30% 426 205 616 500 89


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Tab. 2: Technical properties of rubber crumbs.

Technical properties Value

Specific gravity 0.540

Fineness modulus 2.36%

Water absorption 85%

Tension strength 28.1 MPa

Break point strain 590%

3. Experimental results and discussions

The compressive strengths of rubberized concrete with specimens of rubber crumbs- aggregate replacement 0%, 15% and 30%. were 56.33 MPa, 27.96 MPa, and 16.33 MPa, respectively. Beside the difference in compressive strength, the failure of specimens in quasi-static compression tests also was also different. The normal concrete failed in a more sudden way while the rubberized concrete retained its original shape and cracks extended through the height of the specimens before failure.

The difference in the failure progress of the normal and the rubberized concrete in the impact load test is shown in Fig. 2. The stress-strain relationship of the normal and the rubberized concrete with difference strain rate are shown in Fig. 3a, b and c. It can be seen from this figure that despite the difference in the rubber content, the compressive strength of all specimens increased with the strain rate. Fig.3 also shows that the specimens with higher rubber content (30% Rubberized concrete) has a significant improvement in energy absorption when increasing the strain rate. However, this improvement is not very clear in the remaining specimens with lower rubber contents.

Fig. 1: Static and Dynamic compressive testing systems.

4. Conclusion

This paper presents results of the quasi-static and dynamic compressive tests on normal and rubberized concrete with the variation of the crumb rubber content. The experimental results show that rubberized concrete, especially that of the high rubber content, has great response to impact load. This property of the rubberized concrete should be considered for the future application of this type of concrete.

Fig. 2: Static and Dynamic compressive testing systems.

Fig. 3: Stress-strain relation of a) Normal concrete; b) 15% Rubberized concrete and c) 30% Rubberized concrete.

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References

[1] Siddika A, Mamun M A A, Alyousef R, Amran Y H M, Aslani F and Alabduljabbar H 2019 Properties and utilizations of waste tire rubber in concrete: A review Construction and Building Materials 224 711-31

[2] Pham T M, Zhang X, Elchalakani M, Karrech A, Hao H and Ryan A 2018 Dynamic response of rubberized concrete columns with and without FRP confinement subjected to lateral impact Construction and Building Materials 186 207-18

[3] Elchalakani M, Hassanein M F, Karrech A and Yang B 2018 Experimental investigation of rubberised concrete-filled double skin square tubular columns under axial compression Engineering Structures 171 730-46

[4] Atahan A O and Yücel A Ö 2012 Crumb rubber in concrete: Static and dynamic evaluation Construction and Building Materials 36 617-22

[5] Liu F, Chen G, Li L and Guo Y 2012 Study of impact performance of rubber reinforced concrete Construction and Building Materials 36 604-16

[6] Najim K B and Hall M R 2012 Mechanical and dynamic properties of self-compacting crumb rubber modified concrete Construction and Building Materials 27 521-30

[7] Dong M, Elchalakani M, Karrech A, Fawzia S, Mohamed Ali M S, Yang B and Xu S-Q 2019 Circular steel tubes filled with rubberised concrete under combined loading Journal of Constructional Steel Research 162 105613

CUTE 2020 PAPER: 23


EVAPORATION ESTIMATES

Viktor DUBOVSKÝ1, Dagmar DLOUHÁ1

1Department of Mathematics, Faculty of civil engineering, VSB Technical university of Ostrava, Ludvíka Podéště, Ostrava - Poruba, Czech Republic


Abstract. Although evaporation is one of the main components of the water cycle in nature - it is reported that they make up almost two-thirds of continental precipitation - its measurement or calculation procedures are complicated and burdened with a high degree of uncertainty. This happens due to the complexity of evaporation as a physical phenomenon and a number of factors that affect this process. Furthermore, it is important to note that the fume occurs both from the free water level and from the Earth's surface as well as plants, and these processes need to be distinguished. The above stated then leads to introduction of terms such as evaporation, transpiration, or evapotranspiration. We also distinguish whether we are considering a potential, i.e. possible, or actual, i.e. real, evaporation rate. Both computational methods and measurement methods deal with potential values, which in both cases is due to the fact that it is an effort to simplify the description. The goal of this work is to deal with inaccuracy of computed results and their relation with inaccuracy in measurement of physical quantities influencing evaporation. The interest in such improvements of free water surface evaporation is given by the needs of ongoing hydric recultivation of the former Ležáky – Most quarry, i.e. Lake Most, and also another planned hydric recultivations in the region.

Keywords

Evaporation, Lake Most, Penman-Monteith equation.

1. Equation for Calculation of Evaporation from Free Water Surface

Evaporation influences the global climate and, consequently, each of the areas of human activity, which is manifested by increased interest in the field of its modelling. We divide the methods of calculating the rate

of evaporation into several groups according to the inputs used. Most commonly, the division into models of temperature, radiation, mass transfer, and combined methods is used. The aforementioned quantity of used methods has led the FAO to work towards determining the most appropriate or at least reference method that could be used in the widest possible range of cases under investigation. In this work [2], such chosen method is the the FAO Penman-Monteith equation.

1.1. Penman-Monteith Equation

Penman-Monteith equation in the form of 𝐸𝐹𝐴𝑂 = 0.408∆(𝑅𝑛−𝐺)+𝛾 900𝑇𝑎+273𝑢2(𝑒𝑠−𝑒𝑎)∆+𝛾(1+0.34𝑢2) . (1)

At first glance, it is evident that this is a very complicated relationship, for ordinary users or laypeople it is even possible to talk about a relationship incomprehensible or ungraspable.

Thus a number of different equation to estimate evaporation appear in the technical literature, which dealing with finding relationships less complicated and computationally less demanding. However, equation (1) can still be taken as an etalon to which the results of the other methods can be related.

1.2. Other Selected Equations

In this paper we deal with following equations, selected to represent whole variety of usual approaches, i.e. temperature, radiation, mass-transfer and combined methods.

Šermer equation

𝐸𝑆 = 100,0452𝑇𝑎−0,204 (2)

Priestley-Taylor equation

𝐸𝑃𝑇 = 1.26 ∆∙𝑅𝑛λ (∆+𝛾) (3)

Hargreaves-Samani equation



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𝐸𝐻𝑆𝑢𝑝 = 0,00094𝑅𝑎(𝑇𝑎 + 17,8)√𝑇𝑟 (4)

Penman equation

𝐸𝑃 = ∆∙𝑅𝑛∙𝛾(6.43𝑢2)∙(𝑒𝑠−𝑒𝑎)λ (∆+𝛾) (5)

Beran-Vizina equation

𝐸𝐵𝑉 = 0,2157𝑇𝑎 + 0,1133 (6)

VaV30 equation 𝐸𝑉𝑎𝑉30 = 0.2157𝑇𝑎 + 0.726𝑢2 − 1.2256 (7)

Schendel equation

𝐸𝑆𝑐ℎ = 16.𝑇𝑎𝑅𝐻 (8)

2. Lake Most

Our study area is Lake Most.

Most lake was created by the hydric recultivation of Ležáky – Most quarry, which was situated in the central part of the North Bohemian brown coal basin. The area was formed during the period of tertiary stretches from the flow of the Ohře River in the southeast to the Ore Mountains in the northwest.

Fig. 1: Lake Most.

In the case of Lake Most, it is also possible to consider the fact that it is a lake built without natural inflow and outflow. The income side of the water balance is therefore made up of only precipitation and inlet water, the volume of which is precisely measured by water meters. Losses in the balance represents evaporation from free levels. If we consider that rainfall tributaries from the surroundings/lake basins and the infiltration to the bottom and banks are in balance, the lake can be seen as a 309.4 ha evaporometer. Therefore, we will also compare the results of the calculations with observed fluctuations in the level.

3. Evaporation from Water Surface of Lake Most

In the table the summary of annual evaporation totals is given to illustrate how wide range of computed results could be. For example, in the year 2018 one could expect evaporation in between 826𝑚𝑚 (VaV30 equation) and 1022𝑚𝑚 (Šermer equation estimate), such ahuge difference is crucial in planning flooding of former mine. In the case of Lake Most, with surface area 309ℎ𝑒𝑐𝑡𝑎𝑟𝑒𝑠, the difference of (nearly) 200𝑚𝑚 means (approximately) 600000𝑚3 of water to be purchased.

Tab. 1: Evaporation 2014-2019.

Year 𝑬𝑺 𝑬𝑺𝒄𝒉 𝑬𝑷𝑻 𝑬𝑩𝑽 𝑬𝑷 𝑬𝑭𝑨𝑶 𝑬𝑽𝒂𝑽𝟑𝟎 𝑬𝑯𝑺𝒖𝒑

2014 869 821 877 872 790 751 763 774

2015 937 932 903 875 862 832 810 812

2016 872 832 877 844 803 772 744 776

2017 881 870 884 857 837 802 823 794

2018 1022 1007 976 916 906 879 826 864

2019 831 838 883 762 825 792 735 741

We performed evaporation calculations from the free surface and compared the results with the behavior of the lake Most. The result was a large variance of the theoretical behavior of the water level as a function of the rate of evaporation 𝐸?. For the sake of clarity, the graph (Fig. 2) shows the behavior of the level in dependence on these several selected methods.

Fig. 2: Level development 2014-2019.

4. Conclusion

Considered equation for estimating evaporation rate were tested with respect to the correspondence between their results and result of evaporation etalon given by FAO Penman-Monteith equation. Also their performance under the conditions of simulated measurement error was examined. Finally, the model with the best results was chosen.

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Acknowledgements


References

[1] TRENBERTH, K.E., J.T. FASULLO and J. MACKARO. Atmospheric Moisture Transports from Ocean to Land and Global Energy Flows in Reanalyses. Journal of Climate. 2011, vol. 24, pp. 4907–4924. DOI: 10.1175/2011JCLI4171.1.

[2] ALLEN, R.G., L. PEREIRA, D. RAES and M. SMITH. Crop evapotranspiration-Guidelines for computing crop water requirements-FAO Irrigation and drainage paper 56. United Nation - Food and Agriculture organisation. 1998, vol. 56.

[3] DLOUHÁ, D. and V. DUBOVSKÝ. The Improvement of the Lake Most Evaporation Estimates. Inżynieria Mineralna. 2019, vol. 43, iss. 1, pp. 159–164. ISSN 1640-4920. DOI: 10.29227/IM-2019-02-28.

[4] ANSORGE, L. and A. BERAN. Performance of simple temperature-based evaporation methods compared with a time series of pan evaporation measures from a standard 20 m2 tank. Journal of Water and Land Development. 2019, vol. 41, pp. 1–11. ISSN 1429-7426. DOI: 10.2478/jwld-2019-0021.

[5] LU, J., G. SUN, S. MCNULTY and D. AMATYA. A Comparison of Six Potential Evapotranspiration Methods for Regional Use in the Southeastern United States. JAWRA Journal of the American Water Resources Association. 2005, vol. 41, iss. 3, pp. 621–633. DOI: 10.1111/j.1752-1688.2005.tb03759.x.

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SOME PROPERTIES OF ALKALI-ACTIVATED MATERIALS

Vlastimil BILEK1, David BUJDOS1, Oldrich SUCHARDA1

1Department of building materials and diagnostics of buildings, Faculty of Civil Engineering, VSB – TU of Ostrava, L. Podeste 1875/17, 708 00 Ostrava – Poruba, Czech Republic


Abstract. Alkali activated materials are a very interesting and very wide group of materials. They have good mechanical properties and are also considered to be environmentally friendly materials, because secondary materials are consumed during the preparation of AAM. The durability of AAM is also considered excellent. One of the most important parts of durability is frost resistance. Frost resistance of alkali activated materials is usually considered very good. However, some results show opposite properties and poor frost resistance. The reason may be a different composition of the activator. The content of alkalis is often considered to be the main characteristic of alkali activated materials. However, the SiO2 content can play an important role, too. The paper discusses different results of mechanical properties and frost resistance for different compositions of alkali activator made of sodium water glass with silicate modulus 2 modified by the potassium hydroxide. The role of activator content and water to cement ratio in this phenomenon is discussed.

Keywords

Alkali activated materials, durability, frost resistance.

1. Introduction

Alkali activated materials (AAM) are often considered to be one of the most promising alternatives of Portland cement. They can be prepared for use as secondary materials, such as blast furnace granulated slag (GBFS), fly ash (FA) and some other powders (filler from quarries, filler from recycled concrete [1,2]). The properties of AAM can be very interesting, the strengths can reach high values [2,3] and the durability is also considered very good [4]. However, sometimes some negative properties are also mentioned – they are especially fast setting, high shrinkage

or also some problems with frost resistance [2]. Compared to conventional Portland cement-based concrete, where the water to cement ratio plays a crucial role, in the case of AAM, more factors affect mechanical and durability properties. These are the content of the activator, its composition (especially the ratio between alkalis and silicon oxide, the water to binder ratio, properties of GBFS, FA… [2].

2. Some properties of AAM

2.1. Setting of AAM

The setting of AAM is mainly affected by the composition of the activator. Since the most commonly used activator is based on water glass, this type of activator is discussed in this paper. The start of setting of pastes prepared with different ratios between alkalis – Na2O (N) and K2O (K) and silicon oxide (SiO2) is shown in Fig1. For the dry mass of activator 10% with respect to GBFS dosage.

Fig. 1: Setting of pastes with different mass ratios (K+N)/S in activator.

Obviously, there are some compositions of activator where setting is in a good time interval (mass ration (N+K)/S = 60/40), as well as some ratios where the pastes set very

0

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mass ratio (K+N)/S in activator




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quickly (mass ratio (N+K)/S 80/20 or 90/10. Interesting is the case of activation only with hydroxide (mass ratio (N+K)/S = 100/0) where the setting time is sufficiently long, but the mechanical properties of the mortars are very low.

2.2. Strengths of AAM

The development of the strength of fine-grained alkali activated concrete (Dmax = 4 mm) with N+K = 6 % and different mass ratio (N+K)/S is shown in Fig. 2. It is clear that the highest strength was achieved for N+K/S – 40/60 up to 60/40; the last ratio also showed the optimum setting – Fig. 1.

Fig. 2: Compressive strengths of mortars with different mass ratio (K+N)/S, K+N = 6 %, water / GBFS = 0.50.

2.3. Frost resistance of AAM

Frost resistance (freezing and thawing - F&T resistance) is usually expressed by the F&T-index, which is the ratio strength of F&T-cycled specimens/strength of comparative specimens. The F&T-cycled specimens undergo a number of F&T cycles (4 hours in a -20oC freezer and 2 hours in +20oC water in accordance to the Czech standard CSN 73 1322 Determination of frost resistance of concrete). The F&T indices of alkali-activated fine-grained concrete with N+K = 6% and a different total dry mass of the activator are shown in Fig 3. The specimens were stored in PE-foil up to the age of 28 days, when F&T cycling began. The first set of reference specimens was tested before cycling (PE) and the next set of the specimens was put in water and left there until the end of cycling (W). The number of F&T cycles was 125. Obviously, some problems with frost resistance were recorded. For some mass ratios (N+K)/S, the F&T-indices are very low, especially in the case of the set PE. Mortars with (K+N)/S 34/66, 70/30 show F&T-indices lower than 75 %, which is the limit for frost resistant concrete. Mortar activated only with potassium hydroxide (100/0) disintegrated during the cycles. The F&T-indices with respect to water stored specimens are higher. This is the consequence of poorer bending strengths of water stored specimens. In this case, they are used as a reference specimens. The idea is that the cycled specimens are also partially cured with water and some

increase in strength was expected. The opposite effect occurred. Lower bending strengths of water cured specimens increase the values of the F&T-indices. This phenomenon requires a more detailed study.

Fig. 3: F&T indices of alkali-activated fine-grained concrete with N+K = 6% and a different mass ratio (N+K)/S Conclusion.

As AAMs represent very promising building materials for the future, they have some properties that require further study. Frost resistance is one of them.

Acknowledgements

This work was supported by the project of Conceptual Development granted by the Faculty of Civil Engineering VSB – TU Ostrava.

References

[1] BILEK V., T. OPRAVIL and F. SOUKAL., Searching for practically applicable alkali-activated concretes, 1st Int. Conf. on Advances in Chemically-Activated Materials (CAM 2010), Shi and Shen (Eds), Jinan (China) 2010, pp. 28-35, ISBN: 978-2-35158-101-8

[2] SHI, C., A. FERNANDEZ-JIMENEZ and A. PALOMO. New cements for the 21st century: The pursuit of an alternative to Portland cement. Cement and Concrete Research 41 (2011) pp. 150-763 DOI: 10.1016/j.cemconres.2011.03.016.

[3] SEITL, S., V. BILEK, H. SIMONOVA, Z. KERSNER Mechanical and fatigue parameters of two types of alkali-activated concrete. Key of Engineering Materials Vol. 665 (2016) pp.129-132 DOI:10.4028/www.scientific.net/KEM.665.129.

[4] BERNAL, S.A., J.L. PROVIS. Durability of alkali activated materials: Progress and Perspectives, J. Am. Ceram. Soc., 97 [4] 997-1008 (2014). DOI: 10.1111/jace.12831.

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[M

Pa]

mass ratio (N+K)/S in activator

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34/66 40/60 50/50 60/40 70/30 100/0

Index fb PE Index fb W

F&

T in

dex

[%]

mass ratio (N+K)/S in activator

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STIFFNESS AND DEFORMATION ANALYSIS OF CLT PANELS

Antonin LOKAJ, Pavel DOBES and Kristyna VAVRUSOVA

Department of Structures, Faculty of Civil Engineering, VSB – Technical University of Ostrava, Ludvika Podeste 1875, Ostrava-Poruba, Czech Republic


Abstract. T his paper deals with the determination and comparison of deformation properties – deflection – of CLT (Cross-laminated Timber) panels using the results of laboratory tests, an analytical calculation and numerical modelling. CLT panels are large-format building components composed of cross-oriented solid wood layers. The panels were experimentally tested using a four-point bending test, where a load-deformation curve was recorded. The results of the experimental testing were then compared with a SCIA Engineer numerical model, an ANSYS Workbench numerical model and an analytical calculation.

Keywords

CLT panel, deflection, modulus of elasticity, numerical model, ortrothropy, timber.

1. Introduction

Cross-laminated timber (CLT) is a large-format building component composed of cross-oriented solid wood layers. CLT panels are usually composed of 3 to 7 layers. These layers are glued together in all directions, and polyurethane adhesives are mostly used for gluing them. They are usually made of spruce, but they can also be made of pine or other coniferous wood 1 and 2.

The wood is dried at a moisture content of around 8 % during production, which ensures high resistance to atmospheric influences and prevents cracking. With respect to the drying and gluing technology, they are characterized by their dimensional stability even in the event of significant changes in the moisture of the environment 3.

CLT panels are popular for their excellent strength and stiffness characteristics and also offer excellent fire resistance 4. Relatively high thermal accumulation is another important feature. Cross-laminated timber

structures are naturally diffused open, and that is why they can regulate moisture in the interior.

Thanks to a wide range of positive properties, a wide range of uses are available, both indoors and outdoors. CLT panels currently find applications in civil and residential buildings for the construction of walls, ceilings and roofs 5. Last but not least, they can be combined with other structural systems (e.g. masonry structures) 6.

2. Materials and methods

Beside the analysis of deformation also the stiffness parameters (local modulus of elasticity in bending, global modulus of elasticity in bending) of the CLT panels were determined from the experimental laboratory test. These results are used for analytical calculation of deflection. The test was proceeded according to base principles given in (EN 408+A1, 2012) and (EN 16351, 2017).

2.1. Laboratory sample and experimental laboratory test

The panel CLT 140-3 which consists of 3 layers was selected for testing - the outer layers (40 mm thick) are laid in the longitudinal direction, the middle layer (60 mm thick) is laid in the transverse direction. The geometrical specification of the panel and the test arrangement are shown in Fig. 1.

Fig. 1: Test arrangement of the experimental laboratory test.

The CLT panel is supported and loaded in a similar way as in the four-point bending test given in (EN 408+A1, 2012). The load force value is 2×20 kN = 40 kN, which


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corresponds to approximately 40 % of the estimated maximum load capacity of the panel, where linear flexible material can still be considered. The maximum deflection in the middle of the span is calculated and compared.

The load speed is constant up to the maximum applied load corresponding to 40 % of the estimated maximum load capacity. Deformation w is considered as the mean of the measurements on both sides at the neutral axis. The measured values of deflections corresponding to the individual loading steps are used to create the load-deformation curve. The part of the graph between 10 % and 40 % of the estimated maximum load capacity is used for regression analysis, with a correlation coefficient of 0.99 and better being required.

3. Bending stiffness of CLT panels

The calculation of the bending stiffness (3) of cross-laminated timber is based on the theory of linear elasticity. It is only considered with layers in the loading direction (longitudinal layers); the stiffness of the transverse layers is neglected in the calculation. An effective bending stiffness can be obtained on the basis of the formulas from Annex B of Eurocode 5, which describes the procedure for the stiffness calculation of mechanically connected beams. Steiner's theorem is applied in the calculation, considering a certain degree of compliance between the glued layers (coefficients of shear compliance γ). (𝐸𝐼)𝑒𝑓 = ∑ (𝐸𝑖 ∙ 𝐼𝑖 + 𝛾𝑖 ∙ 𝐸𝑖 ∙ 𝐴𝑖 ∙ 𝑎𝑖2)𝑛𝑖=1

Where

Ei are moduli of elasticity of the individual layers (determined according [4]) [mm2]; Ii are moments of inertia of the individual layers [mm4]; Ai are cross-sectional areas of the individual layers [mm2]; ai are the distances between the center of mass of the individual layers and the center of mass of the panel [mm].

4. Deflection based on calculated bending stiffness

Using the average value of effective bending stiffness (global modulus of elasticity) obtained on the basis of the test data, the maximum deflection according to the linear formula is:

𝑤𝑀𝐴𝑋 = 𝐹24∙𝐸𝐼𝑒𝑓,𝑔 ∙ (3 ∙ 𝑎 ∙ 𝑙2 − 4 ∙ 𝑎3)

5. Numerical model in FEM software ANSYS

Wood is an anisotropic material. Using numerical methods, it is possible to simplify the orthotropic behavior, using cylindrical orthotropy (considering the curvature of annular rings) or rectangular ortotropy (without considering the curvature of annular rings). For this paper, the influence of annular rings, differences between spring and summer wood, local wood faults such as knots and cracks, variable wood structure were neglected in the numerical model.

There are 3 mutually perpendicular directions for wood (see Figure 2) These are defined by the longitudinal direction L (along the grain), the tangential direction T (perpendicular to the grain and tangentially to the annular rings) and the radial direction R (perpendicular to the grain and perpendicular to the annular rings).

Fig. 2: Definition of orthotropic material for wood.

The numerical model in ANSYS Workbench 18.0 simulates the real arrangement of the experiment. The outer load-bearing layers of the CLT panel are modelled as individual planks, the middle non-load-bearing layer is simplistically modelled as one continuous layer. A thin layer of epoxy resin is situated between the individual planks of the outer layers and between the outer and middle layers. This layer represents the bonding together. The CLT panel is supported by two steel I-beams with a flange of width 150 mm. The load is distributed using two steel plates of width 100 mm and thickness 10 mm. The contacts are set as "bonded" between the wooden elements and the epoxy resin. The contacts are set as "frictional" between the steel plates and the panel, and between the left steel I-beam and the panel. The contact is set as "rough" between the right steel I-beam and the panel to prevent horizontal shifting of the CLT panel. The numerical model was created using 3D finite elements. The finite element mesh was automatically generated by the software. The size of the finite element mesh is set to 40 mm with respect to the license constraints of the ANSYS Workbench software. The finite element shape is generated automatically.

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6. Results

The maximal values of global deflections obtained from laboratory tests, an analytical calculation and numerical models from SCIA Engineer and ANSYS are 25.4 mm from experimental laboratory testing, 26.0 mm calculated from the analytical calculation, 27.3 mm from the numerical model and SCIA Engineer and 26.3 mm from the ANSYS model. The Figure 3 shows comparison of the deformation curves gained from the laboratory test of all tested samples and from the analytical and numerical methods.

Fig. 3: Load-deformation curves of CLT 140-3.

7. Conclusion

The paper shows the determination of the bending stiffness of the CLT panels based on test data. The paper also describes how to model CLT panels using orthotropic material in FEM software SCIA Engineer and ANSYS Workbench.

The deflections in the middle of the span were compared. The maximum deflection of the numerical model in SCIA Engineer is 5% higher than the calculation according to the analytical formula with the determined average bending stiffness and 7% higher than the average measured

deflection of the real specimens. The maximum deflection of the numerical model in ANSYS Workbench is 1% higher than the calculation according to the analytical formula with the determined average bending stiffness and 4% higher than the average measured deflection of the real specimens. The small difference is due to the fact that it is not possible to accurately determine the wood strength class of the real specimens and to implement their real material inhomogeneities in the numerical model.

Acknowledgements

This paper has been achieved with the financial support of the Ministry of Education, specifically by the Student Research Grant Competition of the Technical University of Ostrava under identification number SP2018/111.

References

[1] BRANDNER, R., FLATCHER, G., RINGHOFER, A., SCHICKHOFER, G. and A. THIEL. Cross laminated timber (CLT): overview and development. European Journal of Wood and Wood Products. 2016, vol. 74, iss. 3, pp. 331–351. ISSN 0018-3768.

[2] JELEČ, M., VAREVAC, D., AND V. RAJČIĆ, Cross-laminated timber (CLT) – A state of the art report. Gradjevinar. 2018, vol. 70, iss. 2, pp. 75-95. ISSN 0350-2465. DOI: 10.14256/JCE.2071.2017

[3] SCHMIDT, E., RIGGIO, M., BARBOSA, A., MUGABO, I. and F. LALEICKE, Moisture response of a full-scale cross laminated timber panel during environmental simulation: Key factors in design and management, In World Conference on Timber Engineering, WCTE 2018, Center Seoul, South Korea, 2018.

[4] TRAN, T. T., KHELIFA, M., NADJAI, A., OUDJENE, M. and Y. ROGAUME. Modelling of fire performance of Cross Laminated Timber (CLT) panels. Journal of Physics: Conference Series. 2018, vol. 1107, iss. 3.

[5] SHAHNEWAZ, M., TANNERT, T., POPOVSKI, M. and M.S. ALAM. Strength and stiffness of CLT shear walls in platform construction. In World Conference on Timber Engineering, WCTE 2018, Center Seoul, South Korea, 2018.

[6] KATONA, O., KLAS, T., DUCHON, V., BRODNIANSKY, J., BALCIERAK, L. and J. SANDANUS. Experimental study of a four-point bending test on CLT deep beams. Advances and Trends in Engineering Sciences and Technologies II, 2nd International Conference on Engineering Sciences and technologies. 2017. CRC Press/Balkema. Vysoke Tatry, Slovakia. pp. 147-152. ISBN: 978-131539382-7.

0

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0 10 20 30 40 50 60 70 80 90 100 110 120

Loa

d [

kN

]

Deflection [mm]

LOAD-DEFORMATION CURVE FOR CLT 140-3

Specimen 1

Specimen 2

Specimen 3

Specimen 4

Specimen 5

Analytical formula

Numerical model SCIA (linear)

Numerical model ANSYS (linear)

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COMPARISON OF STRESS FIELD AND STRUT-AND-TIE ANALYSES

Dang Bao Tran 1,2

1 Department of Structures, Faculty of Civil Engineering, VSB–Technical University of Ostrava, Ludvíka Podéště 1875/17, Ostrava, Czech Republic

2Department of Civil Engineering, Faculty of Architecture, Thu Dau Mot University, Tran Van On 06, Binh Duong Province, Viet Nam


Abstract. Reinforced concrete deep beams are widely used structural elements in building construction. The Strut and Tie Method, which is recommended by the Eurocode and by the code of American Concrete Institute, is used to calculate the internal forces and to design the deep beams for the ultimate limit state. Stress Field Method can provide more visualized results of deep beams, walls and details for both ultimate and serviceability limit sates. To demonstrate the potential of Stress Field Method, the assessment of well-known example of deep beam with a large opening was performed using both methods in Eurocode context. The results of both analyses were compared. The study has shown (i) wider possibilities to proof structural safety and reliability than the Strut-and-Tie Method would allow, ii) an excellent agreement of the results in the checks viable by both methods, (iii) ability of SFM to perform SLS verifications.

Keywords

Concrete, Deep Beam, Wall, Discontinuity Region, Strut, Tie, Stress Field.

1. Introduction

Strut-and-Tie (STM) [1] and Stress Field Methods (SFM) [2] can be used for the design of discontinuity regions of reinforced concrete members such as deep beams, diaphragms, walls, brackets, areas around opening, anchorage zones, etc. STM is widely used in today’s practice for hand calculations or it is frequently implemented in single-purpose programs or Excel design sheets. It is simple to use with clear link-up with contemporary national standards, but it is limited to the verification of Ultimate Limit State (ULS). Above that, the author’s experience is that even professionals have inadequate knowledge of the main principles for the creation of the models in cases of atypical details. Simplified assumptions of SFM are similar to the ones used in hand calculations, but the method is improved to

allow ductility and Serviceability Limit State (SLS) verifications. SFM can be seen as a generalized Strut-and-Tie Method, in which 2D members with stresses instead of force resultants are considered. The method is based on clear material properties and strength criteria corresponding with the ones used in national codes and regulations, [2]. Despite the obvious benefits, the method is not as widely used in common practice as STM.

2. Objectives

To demonstrate the potential of SFM, the assessment of well-known example of deep beam with a large opening [4] was performed using both methods in Eurocode context [1]. The results of both analyses were compared. The influence of (i) detailing - impact of anchorage, transverse reinforcement in concrete strut, and (ii) model parameters was investigated with respect to ultimate load and mode of failure. SLS verifications were performed by SFM in order to examine to which extend the ULS assessment by STM is sufficient for deep beam design.

3. Specification of analysed Structures

A deep beam with an opening is chosen that had been designed earlier using STM and published by Schlaich et al [4]. The dimensions of deep beam are shown in Figure 1, the factored load Fu=F=3MN, concrete design strength in compression fcd= 17MPa, reinforcement design yield strength fyd= 434MPa.

Schlaich coped the problem of ULS design by splitting the model into left and right part, and by considering two completely different truss models in left part, assuming that each of them would carry a half of the load. Figure 2



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Fig 1: Dimensions and reinforcement layout of deep beam.

(a)

(b)

Fig 2: Strut-and-Tie Model according to [4].

shows the STM of deep beam. One of truss model in left part consists of ties T2 and T9 and corresponding struts, the other truss model in left part contains ties T1, T3 to T8. Using these models for ULS design, Schlaich arrived at the reinforcement layout shown in Figure 1.

The model of deep beam with opening and with the dimensions, materials and the reinforcement according to [4] was analysed by Stress Field method [2]. Deep beam is modelled as a plane stress problem using non-linear finite element method (FEM). The model is composed of (i) 2D concrete elements, (ii) 1D reinforcement elements, (iii) special 2D bond elements, a (iv) rigid body and interpolation constraints between elements. Detail description of components of FEM model including modelling of rebars, loads, interface to Bernouli region, anchorage and bond model can be found in [3]. The topology and the reinforcement layout are shown in Figure 3.

4. Conclusions

The study has shown (i) wider possibilities to proof

structural safety and reliability by SFM than the STM would allow, (ii) an excellent agreement of the results in ULS checks viable by both methods, (iii) ability of SFM to perform SLS verifications.

Fig 3: Structural topology and the reinforcement layout.

0,50 1,50

4,50 2,50

7,00

0,50

1,50

0,70

3MN

0,50

2x2#7 2x2#7

2x5#4

2x7#5

2x7#52x5#4

0,535MN

T1=0,5T

T8

T7

T6T5T3

T4

0,535MN

C1=0,5C

45°

0,535MN

0,535MN

45° T2=0,5T

C2=0,5C

T9

z

0,00 1,00 2,00 3,00 4,00 5,00 6,00 7,00

x0,00

1,00

2,00

3,00

4,00

5,005,00

4,00

3,00

2,00

1,00

0,00

7,006,005,004,003,002,001,000,00

x

z

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Acknowledgements

This outcome has been achieved with the financial support of the project GACR No. 16-08937S “State of stress and strain of fibre reinforced composites in interaction with the soil environment”.

References

[1] EN 1992-1-1 Eurocode 2, Design of Concrete

Structures – Part 1: General rules and rules for

buildings, European Committee for

Standardization, 2015.

[2] MATA-FALCÓN, J., TRAN, D., T.,

KAUFMANN, W., NAVRÁTIL, J. Computer-

aided stress field analysis of discontinuity concrete

regions, In: Proceedings of EURO-C 2018

Computational Modelling of Concrete Structures,

CRC Press, Austria, 2018, pp. 641-650.

[3] NAVRÁTIL, J., ŠEVČÍK, P., KABELÁČ, J., Design, calculation and assessment of walls and

details of concrete structures, Building materials,

Vol. 24, no. 3 (2018), p. 24-28. ISSN 1213-0311.

[4] Schlaich, J; Schaefer, K, Jennewein, M Towards a

Consistent Design of Structural Concrete, PCI

Journal, V.32, No.3, 1987, pp. 74-150.

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PRELIMINARY STUDY ON BENDING STRENGTH OF RECYCLED AGGREGATE CONCRETE BEAMS

Duc-Hien LE1*, Khanh-Hung NGUYEN2, and Quoc-Dung TRUONG2

1Sustainable Developments in Civil Engineering Research Group, Faculty of Civil Engineering, Ton Duc Thang

University, Ho Chi Minh city, Vietnam 2Faculty of Civil Engineering, Lac Hong University, Dong Nai Province, Vietnam

*Corresponding author: [email protected]

Abstract. This study is aimed at investigating the flexural behaviour of reinforced concrete beams incorporating with various levels of recycled concrete aggregate (RCA). Mixing proportion of recycled aggregate concrete (RAC), achieving the target of B15 grade (characteristic compressive strength of 15 MPa) was employed. Three percentages of RCA substituting natural coarse aggregate in mixtures (i.e., 0% -control, 50%, and 75%) were provided for the experiment. First, development of compressive strength of the proposed concrete was estimated and showed that an increase in RCA content resulted in reduction of compressive strength, especially when RCA percentage beyond 50%. Second, the two-point flexural reinforced beam made of RCA was established to examine its flexural behaviour. Obtaining results indicated that shearing failure mode was occurred prior the flexural failure mode. Moreover, there were insignificant reduction of ultimate load (about 1.8%) as increasing RCA replacement.

Keywords

Recycled concrete aggregate, recycled aggregate concrete, shearing, flexural strength.

1. Introduction

Nowadays, many developing countries are facing with serious problems of waste disposals. In fact, there are a number of scholars are highly paying attention on recycling these wastes for sustainable construction materials. Keep in line with this, recycling construction and demolishing wastes to make aggregate for concrete instead of natural one has bring huge benefits in viewpoints of economic and environment [1-3]. It is

recognized that properties of father concrete such as strength, water absorption, shape, and particle’s size are closely related to the performance of RAC. In addition, attached mortar with large content had negative effects on the major properties of RAC such as higher water absorption, lower Los Angeles abrasion coefficient which in turn made concrete be poor in quality [4]. Reduction of attached mortar could be achieved by increasing number of crushing process. The higher water absorption of

recycled aggregate was widely found on higher recycled

aggregate developed from parent concrete having higher

compressive strength and with smaller maximum size of

aggregate [5]. To control the amount of mixing water,

recycling aggregate should be kept in wet surface

condition before use [6, 7]. Generally, the more RCA

presented in mixture, the lower compressive strength of

concrete is [7].

The objective of this study is aimed at investigation

strength development and flexural behaviour of structural

recycled aggregate concrete through two-point loading

beams on simply supports.

2. Experimental program

2.1 Preparation of recycled concrete aggregate; mix proportion; and flexural testing methods

Coarse recycled concrete aggregate collected from disposal of demolishing wastes. These wastes were initially classified and crushed into the particle size of 10-20 mm, which was adequate for the concrete making. The concrete compositions were shown in Table 1, expected achieving the B15 grade concrete (fck = 15 MPa, according TCVN 5574 -Vietnamese standard), consisted of three mix-groups, named at RCA-00, RCA-50, and RCA-75, associated with three level of RCA substitutions (i.e., 0% -control, 50%, and 75%). To control the mixing water, the


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crushed RCA was kept in saturated surface dry (SSD) condition before weighting its dosage. The local river sand with fineness modulus of 2.2 satisfying the ASTM C33 [8] was used as fine aggregate; and the tap water was used for mixing. Tab. 1: Mixing proportion for recycled aggregate concrete used in this

study.

ID. RCA/ NCA w/c OPC

River sand

28-day CS (MPa)

RCA-00 0.0 0.6 293 662 20.2

RCA-50 0.5 0.6 293 662 19.6

RCA-75 0.75 0.6 293 662 14.5

Notes: Aggregates ratio (coarse/fine = 1.77:1); RAC/NCA= ratio of recycled and natural coarse aggregate; w/c = water-cement ratio; CS –compressive strength.

The slump of fresh concrete was measured in range of 80-120 mm, before filling up the 150-mm cubic moulds. After 24 hours of casting, the specimens were demoulded and kept to a saturated-curing apparatus until testing ages (7-, 14-, 21-, 28 days). Each testing result was averaged from three measurements on compressive strength.

2.2 Arrangement of two-point loading test

Fig. 1: Detail of reinforced concrete beam used in this study.

The detail of two-point loading specimen for flexural strength casting from RAC was presented in Fig. 1. The testing beams have its section of 80 mm in width and 150 mm in height; longitudinal reinforcement steel of 410 (reinforcement ratio of 0.75%), located at the corners; and 6-mm stirrup reinforcement with spacing of 150 mm. The specimens were simply supported on rollers, located at 150 mm from each end of the beam.

The beam deflection was measured at mid-beam after each loading increment. Measurement of strain was accessed at two points: stirrup near the support (SG-1) and tensile reinforced steel (SG-2). The concentrated load (P) was applied in a displacement-control procedure at a constant rate of 50 mm/min [9]. Each RAC mixture was replicated on three beams.

Fig. 2: Establishment of two-point testing beam.


3.1 Compressive strength development of recycled aggregate concrete

Fig. 3 shows the compressive strength (CS) development of concrete incorporating with 0% (control), 50%, and 75% as coarse RCA. It can be seen that the 50% RCA concrete had CS to be comparable with the control after 28 days of curing (only 3.5% lower than that of control). However, RCA increased to 75% the CS was 28.6% lower than that of the control.

Fig. 3: Compressive strength development of RAC with changing in RCA percentages.

3.2 Flexural behaviour

3.2.1 Load-displacement measurement

Fig. 4: Load-deflection plots of beams with changing in RCA percentages.

SG1 SG2

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Fig. 4 illustrates typical plots of load-deflection for a RCA-based concrete beam and the detail results were summarised in Table 2 and Fig. 5, indicated that the average ultimate load beams associated with 0%, 50%, and 75% RCA content were minor reduction with 37.32 kN, 37.02 kN, and 36.63 kN, respectively. The ultimate strength of the 75% RCA beam was 1.8% lower than that of the control. High content of RCA had almost no negative effect on the ultimate strength in beam.

Fig. 5: Variations of ultimate load with different RCA percentages.

3.2.2 Load-strain measurement

Figs. 6 and 7 present the load-strain of the longitudinal steel and stirrup respectively. It can be seen that shear reinforcement was yielded (at the strain of 0.2%) at a lower load as the RCA content increased. However, for longitudinal steel was yielded at a similar load for beam made of different RCA substitution.

Fig. 6: Load-strain for tension steel.

Fig. 7: Load-strain for stirrup.

3.3 Cracked patterns

Fig. 8 shows the photos of cracks occurred in beams with changing in RCA content. The shearing cracks were found to develop faster than the flexural cracks, resulted shearing failure mode happened

Fig. 8: Photos of cracked patterns of beams with changing in RCA percentages: (a) RCA-0%; (b) RCA-50%; (c) RCA-75%.

Tab. 2: Results of ultimate load (kN) and associated deflection.

Beam ID %RCA Ultimate load (kN)

Deflection (mm)

M0-1

0%

35.36 5.6

M0-2 37.95 6.8

M0-3 38.64 6.4

M50-1

50%

36.09 5.32

M50-2 39.88 9.17

M50-3 35.08 9.6

M75-1

75%

37.82 6.3

M75-2 35.92 5.4

M75-3 36.15 10.4

4. Conclusion

Several conclusions were drawn from the research work. (1) The higher RCA content the lower compressive strength of recycled aggregate concrete is. However, compressive strength of RAC with 50% RCA was comparable with that of the control (without RCA);

(2) The shearing failure mode was observed for all the

(a)

(b)

(c)

Crack

Crack

Crack

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testing beams;

(3) The ultimate load acting on the testing beams are similar and almost insignificantly affected by RCA content.

References

[1] A.E.B. Cabral, V. Schalch, D.C.C.D. Molin, J.L.D. Ribeiro, Mechanical properties modeling of recycled aggregate concrete, Construction and Building Materials 24(4) (2010) 421-430. [2] F. Afsarian, A. Saber, A. Pourzangbar, A.G. Olabi, M.A. Khanmohammadi, Analysis of recycled aggregates effect on energy conservation using M5′ model tree algorithm, Energy 156 (2018) 264-277. [3] C. Hoffmann, S. Schubert, A. Leemann, M. Motavalli, Recycled concrete and mixed rubble as aggregates: Influence of variations in composition on the concrete properties and their use as structural material, Construction and Building Materials 35 (2012) 701-709. [4] M.S. de Juan, P.A. Gutiérrez, Study on the influence of attached mortar content on the properties of recycled concrete aggregate, Construction and Building Materials 23(2) (2009) 872-877. [5] A.K. Padmini, K. Ramamurthy, M.S. Mathews, Influence of parent concrete on the properties of recycled aggregate concrete, Construction and Building Materials 23(2) (2009) 829-836. [6] J. Yang, Q. Du, Y. Bao, Concrete with recycled concrete aggregate and crushed clay bricks, Construction and Building Materials 25(4) (2011) 1935-1945. [7] M. Etxeberria, E. Vázquez, A. Marí, M. Barra, Influence of amount of recycled coarse aggregates and production process on properties of recycled aggregate concrete, Cement and Concrete Research 37(5) (2007) 735-742. [8] ASTM:C33, Standard Specification for Concrete Aggregates, 2003. [9] M. Arezoumandi, A. Smith, J.S. Volz, K.H. Khayat, An experimental study on flexural strength of reinforced concrete beams with 100% recycled concrete aggregate, Engineering Structures 88 (2015) 154-162.

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WALL CAVITIES BY WET MASONRY REHABILITATION

Jaroslav SOLAŘ1

1Katedra pozemního stavitelství, Fakulta stavební, VŠB-Technická univerzita Ostrava, Ludvíka Podéště 1875/17, 708 33 Ostrava – Poruba, Czech republic

[email protected]

1. Introduction

All Air cavities rank among methods used in rehabilitation of wet masonry. The air cavities can be vertical (in walls) or horizontal (in floors). For detailed description of rehabilitation of wet masonry by means of air cavities see 1, 2 and 3. The wall (vertical) cavities can be on external or internal sides of enclosure walls. Wall cavities which are located on the enclosure wall insides can be located, from the point of view of height: a) Above the floor level. b) Under the floor level. Because this topic is rather complex, only air cavities which are located on the inside of the enclosure masonry above the floor level will be discussed here.

2. Air cavities with ventilation and air flowing out of exterior

The designation and description of images has to be in accord with the template for authors. Air cavities with ventilation and air flowing into/out of exterior

In this case, it is necessary to consider heat losses caused by the internal offsetting wall which is cooled down by the flow of the outdoor air. Heat losses will not be as big as in the air cavity where the air is taken from the interior (see Chapter 2.4), but heat overcladding is still needed for the internal offsetting wall. Because the interior climate is not influenced in this case, this method could be recommended.

In the wall which needs rehabilitation, masonry will be removed up to 800 mm above increased moisture and joints will be cleared down to 20 mm. If it is possible thanks to cohesion of the remaining mortar and load-carrying capacity of the masonry, it is recommended to keep the joints open in order to crease as big surface for evaporation as possible.

A heat and thermal assessment is needed for the designed air cavity. The assessment should cover following aspects:

a) Assessment of the heat transmission coefficient, U W.m-2.K-1 , for the inside wall b) Assessment of the heat factor of the internal surface,

fRsi, in risk places

c) Assessment of water condensation in the middle

of the inside wall d) Assessment of the air flow and condensation of water

vapours in the air gap

e) Assessment of condensation of water vapours on the inside surface of the enclosure wall (to be rehabilitated).

For detailed description of the heat and technical assessment mentioned in a) through c) above see Chapter 2.1. A suitable software such as MEZERA 2015 7 will be used to calculate the air flow and possible condensation of water vapours in the air gap and to assess condensation of the water vapours on the inside surface of the enclosure wall (which needs rehabilitation). Then, several alternatives can be analysed and the best thickness of the air gap can be proposed. It is also possible to design ventilation holes (the quantity, size and surface) which would prevent condensation and which would create sufficient air flow in the gap that is needed for withdrawal of the water vapours. The bottom of the air gap should be properly insulated (for instance, using EPS Perimeter or extruded polystyrene). This will reduce negative impacts of the ambient air on the footing bottom in the moist wall and floor in the room during winter. It is also advisable to overclad a part of the wall in the air gap where the moisture has been removed (for instance, up to 200 mm).

A detailed analysis of the air flow in the air cavity could by performed using CFD (computational fluid dynamics), for instance, in ANSYS − FLUENT 8. The method should be similar to that which is described for horizontal air cavities (in floors) in 9.

Fig. 1 shows development of temperature in a vertical air

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cavity with ventilation with takes air from exterior and supplies air to exterior, and without heat overcladding on the air cavity bottom.

Fig. 2 shows examples of results of the assessment of the air flow and possible condensation of water vapours in an air gap and condensation of the water vapours on the inside surface of the enclosure wall.

3. 4 Air cavities with ventilation and air flowing out of interior into exterior

This method reduces air humidity in the interior. The problem is that much heat losses occur in winter. This means, ventilation flaps should be installed on suction holes which would prevent heat losses from occurring, to a certain extent at least. If the flaps are shut off for a long time, the system will fail. In summer that the temperature of the ambient air is higher than that inside the building, the air flow in the reverse direction – from the exterior into

the interior. This solution is applicable under certain conditions only. In the wall which needs rehabilitation, masonry will be removed up to 800 mm above increased moisture and joints will be cleared down to 20 mm. If it is possible thanks to cohesion of the remaining mortar and load-carrying capacity of the masonry, it is recommended to keep the joints open in order to crease as big surface for evaporation as possible.

Technical assessment should be carried out for the cavity. Items of the technical assessment are, in fact, same as in Chapter 2. 3 (the air cavity with the air taken from/supplied to the exterior):

a) Assessment of the heat factor of the internal surface, fRsi , in risk places

b) Assessment of condensation of water vapours on the inside surface of the enclosure wall (to be rehabilitated)

c) Assessment of the air flow and condensation of water vapours in the air gap

For detailed description of individual parts of the heat and technical assessment see above.

References

1 Balík, M. a kol.: Odvlhčování staveb. 2. přepracované vydání. Grada Publishing, a. s., Praha, 2008. 307 stran. ISBN 978-80-247-2693-9.

2 Solař, J.: Odtrańování vlhkosti. Sanace vlhkého zdiva. Grada Publishing, a. s., Praha, 2013. 112 stran. ISBN 978-80-247-4708-8.

3 Solař, J.: Calculating the air flow velocity in air cavities iv walls. Conference 20th International Conference on Engineering Mechanics (EM) Location Svratka. Czech Republic. May 12. – 15. 2014.

4 ČSN 73 0540 − 2 Tepelná ochrana budov – Část 2: Požadavky (2011).

5 Svoboda, Z.: TEPLO 2015. Výpočtový program pro PC.

6 Svoboda, Z.: AREA 2015. Výpočtový program pro PC.

7 Svoboda, Z.: MEZERA 2015. Výpočtový program pro PC.

8 ANSYS − FLUENT. Výpočtový program pro PC.

9 Solař, J., Kalousek, M.: Posouzení proudění vzduchu v podlahové vzduchové mezeře metodou CFD. Tepelná ochrana budov č. 2/2008. ISSN 1213-0907.

Fig. 1: An example of temperature behavior in structures forming a vertical ventilated cavity with air inlet and outlet to the exterior, without thermal insulation of the bottom

of the cavity. Output from AREA 2015 [6].

Fig. 2: Demonstration of results of assessment of air cavity ventilated with air inlet and outlet to exterior. Output from the MEZERA 2015 program [7].

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ADVANCED MODELLING OF THE INTERACTION BETWEEN THE FOUNDATION STRUCTURE AND THE SUBSOIL

Lukas DURIS1, Eva Hrubesova1

1Department of Geotechnics and Underground Engineering, Faculty of Civil Engineering, VSB Technical University

of Ostrava, L. Podeste 1875/17, Ostrava, Czech Republic

[email protected], [email protected],

Abstract. The interaction of the subsoil with the structure is a complex problem involving both the design of the structure and the assessment of its foundation. This paper is focused on the evaluation and numerical simulation of the experimental loading of a concrete slab which is in contact with ground subsoil. The loading of the slab was done by axial force over a steel distribution plate. In total, three concrete slabs of reinforced concrete with different amounts of fibres were assessed. During the experiment, the deformations of the slab and the stresses in the ground were measured. A spatial numerical model was constructed on the basis of experimental measurements. The specialized Midas NX GTS program was used for modelling geotechnical problems. The aim was to build a model that would best characterize the measured results with respect to the use of contact elements and material models.

Keywords

Concrete, deformation, interface, Midas GTS NX, numerical model, subsoil.

1. Introduction

Each building structure is usually divided into basic building parts such as the foundation, load-bearing structure, roofing, cladding, etc. One of the most important parts is the foundation structure, which has the task of transferring loads from the upper structure to the subsoil. Two different materials are in contact with each other and there is interaction between the soil and the structure. To ensure the correct functioning of the foundation of the building, specific characteristics of the structure are necessary such as the quality of the rock massif. In cases of more complex or vast structures, quality is examined through a geotechnical survey. In order to create a

foundation, it is necessary to determine the load-bearing capacity of the foundation soil, which is determined primarily by the strength characteristics of the subsoil. However, the deformation characteristics of the bedrock are also important for the evaluation of the limit state of capacity.

In connection with the research of the interaction of the structure with the subsoil, experiments were carried out on a test stand at the Faculty of Civil Engineering of the Technical University of Ostrava. The aim of the tests was to observe the behaviour under loading of various concrete slabs in contact with the ground. During ongoing research, concrete slabs of plain and reinforced concrete were tested. Some selected parts of the experiment have been presented before. For example, the stress analysis in the subsoil of the slab was presented by Hrubesova [1], Lahuta [2]. A similar topic is addressed, for example, in a paper by Hegger at al [3]. In this paper, they focus on punching behaviour of reinforced concrete slabs. This slab had dimensions of 0.9x0.9x0.2m and part of the slab was a concrete column 0.15x0.15m. The whole experiment was carried out on a subsoil of sand in a test box. It was an experimental model of five types of slabs.

The aim of the paper is to analyze the possibilities of the numerical modeling by geotechnical software an interaction of the concrete structure with the subsoil based on measurements performed on a test stand.

2. Concrete slab testing

The aim of the experiment was to determine the limit load-bearing capacity of a 2.0 m x 2.0 m square concrete slab with 0.15 m thickness. It was a thin concrete slab with a locally-placed load at the centre of the slab. The loading force was transmitted to the slab by means of a steel plate with dimensions of 0.4 x 0.4 m. The aim of the experimental measurements was not only to verify the ultimate load-bearing capacity, but also to verify the effect


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of individual concrete mixtures or reinforcement. The concrete used was class C20/25 with 25 kg of fibre per cubic of concrete. Laboratory tests verified the basic parameters of the unreinforced fibre concrete mixture.

The average cube strength with 25 kg/m3 of added fibre was measured at 30.9 MPa. The tensile strength was not evaluated for the slab material. The slab was loaded centrically. A total of 8 load cycles were initiated until the complete failure of the slab. The maximum load force achieved was 593 kN. During loading, deformations were measured on the surface and stress under the slab.

3. Modelling of the slab – subsoil interaction

The numerical solution of complex problems using the finite element method is a common practice today. On the basis of the data obtained from measurements on the experimental slab, a backward numerical analysis was performed. The Midas GTS NX computing system was used for this analysis.

The elastic-ideally plastic Mohr-Coulomb material model was used to describe the soil behaviour in the numerical model, considering the increase of the stiffness of the subsoil towards the depth below the slab. Several special models have been developed for nonlinear concrete behaviour. Midas offers a variety of material models, but not all are suitable for modelling structures.

The elastic (Elastic) and elastic-plastic (Mohr-Coulomb (M/C) and Drucker-Prager (D/P)) variants were considered for the slab material. The input strength parameters of the slab material for the constitutive models taking into account plastic deformation were determined based on the Coulomb’s law. Vertical deformation on the top surface of the slab were considered as the main evaluation criterion of the inverse numerical calculation.

The comparison of the measured values with the calculated values of vertical displacements of the slab is shown in Figure no. 1. The model results show that extreme settling values almost match the measured values in all analyzed load steps. The perimeter of the slab was released (lifted) from the subsoil during the experiment, with the maximum lift values at the corners of the slab. This phenomenon was not achieved in the model calculation.

Contact elements are used in numerical models to assess the mutual behaviour of the structure-soil contact. These elements simulate the transition between two materials (e.g. concrete-soil) and take into account the fact that the contact of the soil with the concrete slab will cause shear failure much sooner than in the soil itself. A contact element is a zero-thickness element. Contact elements are most often defined by their virtual thickness tv and a reduction coefficient R. The reduction coefficient R reduces the normal stiffness, shear stiffness and shear parameters of the contact.

Fig. 1: Vertical deformation on slab surface - comparison with model.

4. Conclusion

The topic of the article is the numerical modelling of the interaction of the concrete structure with the subsoil. On the basis of experiments a retrospective analysis of the interaction of the structure-subsoil was calculated with the use of geotechnical software. Three variant constitutive concrete slab models were tested. The subsoil parameters were calibrated to the maximum measured plate settling values. The effect of the contact elements between the concrete slab and the soil was analysed on this model. In this case, a significant influence of the use of contact elements was not confirmed in quantitative comparison with the measured values.

Acknowledgements

This article was prepared with the support of a research project at VSB TU of Ostrava for the year 2019 guaranteed by the Ministry of Education, Sports and Sport of the Czech Republic

References

[1] HRUBESOVA, E., M. MOHYLA, H. LAHUTA, et al. Experimental Analysis of Stresses in Subsoil below a Rectangular Fiber Concrete Slab †. Sustainability 2018, 10, 2216.

[2] LAHUTA, H, et al. Assessment of Fiber Reinforced Concrete Slab and Subsoil Interaction-Experiment. Key Engineering Materials. Vol. 761. Trans Tech Publications, 2018.

[3] HEGGER, J., M. RICKER, B. ULKE, M. ZIEGLER. Investigations on the Punching Behaviour of Reinforced Concrete Footings. Engineering Structures, Volume 29, Issue 9, 2007, Pages 2233-2241, ISSN 0141-0296, DOI: 10.1016/j.engstruct.2006.11.012.

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ANALYSIS OF THE TIMBER FRAME CONNECTION WITH DOWEL TYPE MECHANICAL METAL FASTENERS

Marek JOHANIDES1, Lenka KUBÍNCOVÁ1, Antonín LOKAJ1, David MIKOLÁŠEK1

1VŠB – TU Ostrava, Faculty of Civil Engineering, Ludvíka Podéště, Ostrava – Poruba, Czech Republic

[email protected]

Abstract. Timber as a material in the construction industry gets more and more into the foreground for the construction of various structures. To improve the properties of timber, new composite materials or new joints, which ensure better bearing capacity and stiffness of the structure, are developed. One of the uses of timber is, among other things, the construction of hall buildings, where are interesting frame connections, which are joints of the diaphragm beam and frame column. The timber frame connections can be solved in several ways, for example by means of glued rods, toothed - plate joints, by means of pinned joints and a frame connection made by a V-shaped frame column. In common practice, these are the types of joints between the diaphragm beam and the frame column. However, the object of this contribution is a frame connection where the connection of the frame column and the diaphragm beam is created by means of the Rothoblaas VGS11400 screws, which are not normally used as fasteners for this type of joint. The reason for choosing this fastener is to find out how it behaves in this type of construction and to compare it with normative documents, taking into account the use of this type of joint in practice.

Keywords

Timber, timber frame, numerical analysis, experimental test,

screws, joints, FEM model.

1. Description of the issue

As mentioned in the previous chapter, the subject of this article is the timber frame connection of a supporting timber frame of a single nave hall. The solved frame connection (Fig. 1:) is designed as a joint of a pair of frame columns and diaphragm beam from glued laminated timber GL24h. The frame columns are 120/700 mm at the frame connection and the diaphragm beam is 180/700 mm. The joint of the two-part frame column and the diaphragm

beam is designed as a bending rigid joint; the beam is inserted between the parts of the frame column. Assembly connection is realized using Rothoblaas VGS11400 screws with a diameter of 11 mm and a length of 400 mm. The screw arrangement is made in two concentric circles with a radius r1 = 273 mm in the number of 24 screws for the outer circle and with a radius r2 = 218 mm in the number of 20 screws.

Fig. 1: Timber frame connection.

1.1. Numerical analysis of the timber frame connection

The aim of the numerical analysis was to elucidate the behavior of the frame connection caused by the load from the bending moment. The analysis was performed by manual calculation and using numerical FEM models created in Scia Engineer 17.1 and ANSYS 18.1.


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1.2. Evaluation of the experimental test During the experimental testing of the frame connection structure, the frame column was damaged during the third load cycle, with the occurrence of a crack (Fig. 2:). The cause of this disturbance was imperfect boundary conditions where the increased vertical (load) force increased the horizontal forces. These horizontal forces were caused by the friction between the timber frame column and the steel structure simulating boundary conditions. The loading of the structure continued further until the joint was broken, because the crack had no significant effect on the load bearing capacity of the joint.

Fig. 2: Crack in the bearing of column frame during loading.

Fig. 3: View of broken diaphragm bam.

Fig. 4: View of broken diaphragm bam and column frame.

1.3. Loading process

In the graph 1: the red curve is linear abscissa using the rotational stiffness Kr,ser = 19,50 MNm/rad (calculated as the characteristic value according to the standard ČSN EN 1995-1-1) at the point of contact of the diaphragm beam and the frame column. Depending on the interleaved linear abscissa indicating the inclination (red curve) over the loading and relieving cycle, it was possible to estimate the stiffness of the entire frame connection system, including the steel structure and the frame connection.

When separating the displacements, associated stiffnesses, and mathematically converting the displacement and forces into rotation and moment, its inclination indicates the searched stiffness, which will be used to determine the rotational and translational stiffness to compare stiffnesses used in the case of beam models. When comparing the results from the numerical FEM model that was just loaded and the physical test, it is confirmed that the consistency in the resulting stiffness is good. On the Graph 1 it is the same inclination of the grey curve (solid line, experimental test) orange (dashed) and blue (long dashed) curves (numerical values).

Graph 1: Strain stress curves for frame connection.

1.4. Comparing the results

Individual ways of carrying out the timber frame connection (manual calculation, numerical FEM models and experimental testing) was compared to each other through some parameters, such as the collapse force of the timber frame connection construction and the deformation.

Testing of the frame connection was also focused on the way of its failure and the force causing the collapse of the structure. The assumption was that, depending on numerical calculations, the disturbance would occur in the tension perpendicular to the fiber, and this was confirmed during the experiment. In the fourth phase, the examined joint was broken.

The disturbance occurred in the tension perpendicular to the fiber at the top of the diaphragm beam and it confirmed the assumptions from the numerical analysis. The joint failure occurred at a force of F = 233,30 kN.

The maximum force that the timber frame connection can withstand was determined in several ways. The individual

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values of the collapse force and the approaches by which the forces were determined are given in the (Tab. 1:). The most resistant is the timber frame connection in the case of the numerical model with a material-linear approach from ANSYS 18.1. However, during the experiment, it was shown that the failure occurred at a measured load force of F = 233,30 kN, which is approximately 1,56 times the design load bearing capacity determined according to the standard ČSN EN 1995-1-1. Tab. 1: Comparing of the load forced causing the collapse of the

structure.

Calculation method

Force caused the collapse F

[kN]

Bending moment caused the collapse

M

[kNm]

Multiplier of M

Standard approach EC5

149,10 223,65 -

Ansys – linear calculation

308,89 469,51 2,09

Ansys – nonlinear calculation

157,94 240,07 1,07

Physical test 230,30 349,95 1,56

2. Conclusion

The article was focused on the problems of joint of the diaphragm beam and the frame column using mechanical fasteners. In this case, the diaphragm beam and the frame column are connected using the Rothoblaas VGS11400 screws. The thesis required the creation of numerical models, which were the basis for experimental testing and subsequently were used for comparison. Through experimental testing it has been shown that Rothoblaas VGS11400 screws, which are not normally used for timber frame connections, have

sufficient bearing capacity for this use. In this case, the higher bearing capacity was demonstrated than the bearing capacity determined by normative documents ČSN EN 1995-1-1. This assumption is expected because the standards assume, in addition to the maximum given bearing capacity, a certain reserve to break the joint or element. The frame connection was disturbed during the experiment by tension perpendicular to the fiber in the upper corner of the diaphragm beam, which only supported the correctness of the numerical model. The test structure was without any reinforcement of the diaphragm beam, with its reinforcement the bearing capacity would increase. To confirm this theory, however, it is necessary to carry out further experimental measurements with and without the reinforcement of the diaphragm beam. In the framework of cooperation with the practice and research activity at the VŠB - Technical University of Ostrava, Faculty of Civil Engineering, it is expected to continue with this study by other physical experiments. These tests would be aimed at comparing the efficiency of timber frame connections created by screws and pins.

Acknowledgements

Experimental measurement and research were realized thanks to the Department of Structures of the VSB - Technical University of Ostrava, Faculty of Civil Engineering, and financial support of companies EXTEN CZ spol. s.r.o, ROTHOBLAAS and INGENIA. Acknowledgments include the Laboratory of Building Materials, the Department of Structural Mechanics of the VSB - Technical University of Ostrava, Faculty of Civil Building Engineering, and colleagues working in the Experimental Center of the VSB - Technical University of Ostrava. Acknowledgments also include the AVC Promotion Center and namely doc. Ing. Radim Halama, Ph.D. from the VSB - Technical University of Ostrava, Faculty of Mechanical Engineering for realization of measurements IDC image data correlations.

The project was supported by the Student Grant

Competition VSB - TUO. The project registration number is SP2020/158.

References

[1] GONZA´LEZ FUEYO, J. L., M. DOMINGUEZ, J. A CABEZAS a M. P. RUBIO. Design of connections with metal dowel-type fasteners in double shear. RILEM. 2009, 14. DOI: 10.1617/s11527-008-9389-3.

[2] BOUCHAI R, A., P. RACHER a J. F. BOCQUETRECEIVED. Analysis of dowelled timber to timber moment-resisting joints. RILEM. 2007, 16. DOI: 40(10):1127-1141.

[3] Danielsson, H., Crocetti, R., Gustafsson, P.J.&Serrano, E., Brittle failure modes in nailed steelplateconnections, WCTE 2016 - World Conference onTimber Engineering.

[4] Piazza, M., Polastri, A., Tomasi, R., Ductility of timber joints under static and cyclic loads, Proceedings of the Institution of Civil Engineers - Structures and Buildings (2011), vol. 164(2), pp. 79–90, ISSN 0965-0911.

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EXPERIMENTAL TESTING OF MASONRY SUBJECTED TO

CONCENTRATED LOAD IN THE DIRECTION OF BED JOINTS

Marie KOZIELOVA1, Lucie MYNARZOVA1, Petr MYNARCIK2

1Department of Structures, Faculty of Civil Engineering, VŠB – Technical University Ostrava, Ludvíka Podéště 1875/17, 708 00 Ostrava-Poruba, Czech Republic

2Centre of Building Experiments, Faculty of Civil Engineering, VŠB – Technical University Ostrava, Ludvíka Podéště 1875/17, 708 00 Ostrava-Poruba, Czech Republic


Abstract. The article specializes in experimental research of masonry restoration using additional reinforcement by prestressing. It is an effective method to eliminate cracks incurred due to changing terrain. This may happen for example due to undermining of the area after coal mining activities or nearby underground collectors in municipalities, tunnels, etc. Experimental measuring was carried out in laboratory facilities designed specifically for testing the triaxial state of stress of the masonry. Within these experimental tests, laboratory measuring of mechanical masonry properties was made, and deformation characteristics were defined based on calculations. The data obtained were then used for numerical models that are part of the masonry examination in the course of its restoration. In conclusion, measuring results were summarized and input values for masonry modelling were suggested.

Keywords

Masonry, brick, mortar, compressive strength of masonry, flexural strength of masonry, testing, prestressing, numerical model.

1. Introduction

Experimental masonry samples were processed in the prepared laboratory facility designed to test the triaxial state of stress of a prestressed masonry corner (Fig. 1), with a plane view of 900 x 900 mm, total height of the laboratory facility was 1,550 mm. The walling material was a solid clay brick with the production size of 290 x 140 x 65 mm and lime mortar. Masonry thickness was 440 mm. Masonry samples were three, samples MS_1, MS_2 and MS_3. Masonry surface was not plastered. Actual

height of samples after the brickwork was 850 and the length 850 mm.

Fig. 1: Laboratory facility for triaxial state of stress testing.

Anchoring plates of 300 x 300 mm were laid on a mortar layer to transfer pressures to masonry from the prestressing bar. Values of prestressing forces were selected safely with respect to the quality of mortar filled in joints from 10 to 50 %, or 70 % from the overall masonry compression strength. The aim of this testing was not only to measure deformations, but also to monitor masonry behaviour at the point of local stress due to gradually increasing prestress. The testing performed simulated behaviour of reinforced masonry by prestressing rope at the moment of tensioning, so these were short-term tests.



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Fig. 2: Deformations from prestressing force.

The comparison of resulting deformations for individual test samples in the middle of the anchoring plate and on its edge is shown in Fig. 2. Values are stated for the load corresponding to 50 % of the masonry compressive strength only (Fig.3).

Fig. 3: Numerical model of masonry deformation.

2. Conclusion

This article presents the research focused on the option to utilize masonry restoration using sufficient reinforcement by prestressing. Experiments included three tests of the masonry under concentrated stress due to prestressing force, including laboratory tests defining selected mechanical and deformation characteristics. Results of laboratory testing were then used for input data of material

models for advanced analyses of prestressed masonry. Numerical simulations made grasped the experiments carried out. Differences between experiments and numerical calculations may be considered small in case that effective modulus of elasticity and composite modulus of elasticity are used.

Acknowledgements

Works have been supported by funds of the conceptual development of science, research and innovations granted to VŠB-TUO by the Ministry of Education, Youth and Sports of the CR.

References

[1] SHIH, Y.-F., Y.-R. WANG, K.-L. LIN and C.-W. Chen. Improving non-destructive concrete strength tests using support vector machines. Materials. 2015, vol. 8, pp.7169-7178. DOI: 10.3390/ma8105368.

[2] ŁATKA, D. and P. MATYSEK. The estimation of compressive stress level in brick masonry using the flat-jack method. Proceedings of the 9th International Conference on Analytical Models and New Concepts in Concrete and Masonry Structures (AMCM). Gliwice: Poland. DOI: 10.1016/j.proeng.2017.06.213.

[3] LIN, K., Y. Z. TOTOEY, H. J. LIU and C. L. WEI. Experimental characteristics of dry stack masonry under compression and shear loading. Materials. 2015, vol. 8, pp. 8731-8744. DOI: 10.3390/ma8125489.

[4] CSN EN 1996-1-1, Eurocode 6: Design of masonry structures – Part 1-1: General rules for reinforced and unreinforced masonry structures, 2013.

[5] LOURENCO, P. B., D. V. OLIVEIRA, P. ROCAAND and A. ORDUNA. Dry Joint Stone Masonry Walls Subjected to In-Plane Combined Loading. Journal of Structural Engineering. 2005, vol. 131, pp. 1665-1673. DOI: 10.1061/(ASCE)0733-9445(2005)131:11(1665)

[6] LOURENCO P. B., G. MILANI, A. TRALLI and A. ZUCCHINI. Analysis of masonry structures: review of and recent trends in homogenization techniques. Canadian Journal of Civil Engineering. 2007, vol. 34, pp. 1443-1457. DOI: 10.1139/L07-097

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ELASTIC POST-BUCKLING BEHAVIOR OF PLATES WITH AN INTERMEDIATE STIFFENER – TWO-STRIP MODEL SOLUTION

Miroslav ROSMANIT1

1Department of Structures, Faculty of Civil Engineering, University, VSB – TU Ostrava, L. Podeste 1875, Ostrava, Czech Republic

[email protected]

Abstract. The two-strip model can be used to derive simple, parametric expressions describing the distortional post buckling behavior of uniformly compressed simply supported square plates with one central intermediate stiffener. The initial imperfections in the shape of the distortional buckling mode is considered. The load-deformation characteristic is studied. The other limitation is to ideal stiffeners in which the centroid corresponds to the mid-surface of the plate. The post-buckling to pre-buckling in-plane stiffness ratio of the ideal flat plate with stiffener must be known. It is shown how this ratio can be determined. The finite element simulations of plates with imperfections is used. It turns out that the post-buckling behavior is more sensitive to inaccuracies in the assumed deflection shape than the buckling stress. The analytical approximation of the deflection shape which is sufficient for description of post-buckling load-deformation behavior is presented. Analytical solution is corresponding to the results obtained by the finite element simulations.

Keywords

Post-buckling, compressed plates, intermediate stiffener, analytical and numerical solutions.

1. Introduction

The elastic post-buckling behavior of simply supported rectangular plates (without intermediate stiffeners) can be described by simple parametric formulas [1]. Such formulas are not available for plates with intermediate stiffeners. This paper shows how a simple two-strip model, which was developed for plates without intermediate stiffeners [2] can be modified to derive parametric formulas predicting the distortional post-buckling behavior of plates with intermediate stiffeners and initial imperfections in the shape of the distortional buckling

mode (see Figure 1). The paper is limited to the prediction of the elastic load-deformation behavior of square, simply supported plates subjected to uniaxial compression, with one central ideal stiffener, whose centroid corresponds to the mid-surface of the plates.

Fig. 1: Model of simply supported square plate with one (ideal, central) intermediate stiffener.

The shape of the stiffeners is undetermined since the stiffeners are characterized by their area Ast and their moment of inertia Ist. Local buckling of the stiffeners is not considered. The loaded edges of the plate are forced to remain straight. The unloaded edges are stress free, that is, free to wave in plane. The sign convention used is that tension stresses and strains are positive, compression stresses and strains negative.

In the two-strip model [2] there are two edge strips and one central strip. The load carried by the plate is the sum of the load carried by the separate strips. The central strip behaves like a classical Euler column. The two edge strips always remain straight and together constitute a single element of the system. The only compatibility requirement taken into account is that the central and edge strips experience the same in-plane shortening. The width of the edge strip can be determined from the ratio of post-buckling to pre-buckling stiffness of the perfectly flat plate. This paper is motivated as a first step in getting a better understanding in the behavior of stiffened compression flanges in cold-formed steel deck sections.

Fwmax

a

umax

xz

y

b

a)


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2. Analytic calculation and FEM simulations

2.1. Calculation of the buckling stress

An approximate value of the buckling stress of a plate with a central stiffener can be determined using the energy method [3]. In this method the deflection shape of the buckled plate is approximated by a trial function in which the work done by the applied loads equals to the strain energy due to bending. Using the two-strip model approach, the critical stress can be derived.

Combining the new derived results with the previously obtained formulas [2] and knowing the post-buckling to pre-buckling in-plane stiffness ratio (E*/E) of the ideal flat plate with stiffener a special parameter Cw relating the maximum out-of-plane deflection wmax and the maximum out-of-plane imperfection w0;max of the real plate to those of the central strip can be derived.

2.2. Finite element model and parameter study

A numerical parameter study has been carried out with the finite element program ANSYS. Eigenvalue calculations have been carried out to determine the buckling stress and shape, geometrical non-linear calculations to determine the elastic load-deflection behavior. For the geometrical non-linear load-deflection calculations imperfections in the shape of the distortional buckling mode were included, scaled to set the maximum initial imperfection w0;max, with the amplitudes w0;max = 0.005t and 0.25t mm. The plate width and length, plate thickness, Young’s modulus and Poisson’s coefficient were kept constant in the study: a = b = 100 mm, t = 1 mm, E = 210 000 N/mm2, ν = 0.3.

Fig. 2: Schematic view of FEM model: a) boundary conditions; b) initial imperfection in shape of distortional buckling mode.

The stiffener has been modelled as a beam. Cross-sectional properties of the stiffener have been varied Ast = 0, 5, 10, 20, 50 and 100 mm2 and Ist = 0, 5, 10, 20, 50 and 100 mm4. For all these stiffeners the first buckling

mode of the plate is distortional. In the model Mindlin shell elements SHELL43 and Euler beam elements BEAM4 were used. Both element types have six degrees of freedom at each node: translations in the nodal x-, y- and z-directions and rotations along the nodal axes. The mesh density for each plate was 40 x 40 elements. All boundary conditions and axis conventions are presented in Figure 2. Other information about the model is given in [3].

Using finite element simulations, for a given umax;FEM and w0;max, the corresponding FFEM and wmax;FEM can be determined directly. In this paper the values for Au;FEM and AF;FEM have been calculated for (rather arbitrarily chosen) values of w0;max = 0.005t and umax = 1.2ucr;FEM. From the thus determined Au;FEM and AF;FEM values the values for (E*/E)FEM and Cw;FEM can be determined.

It was found that (E*/E)FEM decreases with increasing Ast and Ist ,varying between 0.401 for a plate without stiffener and 0.2452 for a plate with Ast = 100 mm2 and Ist = 100 mm4 (see also Table 1). Based on curve fitting of FEM results the following empirical expression is proposed to calculate E*/E as a function of Ast and Ist.

3. Conclusion

The analytically determined value for σcr, is slightly higher than the values σcr;FEM found with ANSYS. The largest error, occurring for plates with Ast = 0 mm2 and Ist = 100 mm4, was less than 2%, confirming the statement by Timoshenko and Gere [4] that a two term approximation of the buckled shape is accurate enough for the calculating of the buckling stress. It was found that the buckling stress increases with increasing Ist and decreases with increasing Ast. Tab. 1: Ratio E*/E /(E*/E)FEM depending on Ast and Ist.

Ast

Ist

→

0

[mm4]

5

[mm4]

10

[mm4]

20

[mm4]

50

[mm4]

100

[mm4]

0 [mm2] 1.000 1.003 1.006 1.014 1.034 1.055

5 [mm2] 1.001 1.003 1.006 1.013 1.031 1.052

10 [mm2] 1.002 1.004 1.006 1.011 1.028 1.049

20 [mm2] 1.005 1.006 1.007 1.011 1.024 1.043

50 [mm2] 1.018 1.017 1.016 1.016 1.017 1.029

100 [mm2] 1.038 1.034 1.031 1.026 1.014 1.009

Fig. 3: Variation of (E*/E)FEM depending on Ist.

a)

x

y

z identical

uz= 0

uz= 0

uz= 0

ux u= = 0z

uy= 0ux

beam elements

shell elements

Fw0

b

a = b

ents

nts

b)

x

y

z

w0;max

0.0

0.1

0.2

0.3

0.4

0.5

0 20 40 60 80 100I st [mm4]

(E*

/ E) FEM

A st = 100 mm2

A st = 0 mm2

A st = 20 mm2

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Table 1 shows the determined ratios of E*/E to (E*/E)FEM. It can be seen that the (E*/E)FEM values are slightly overestimated. Table 2 shows the ratios of determined Cw to Cw;FEM. It can be seen a slight under-estimation of the Cw;FEM values.

Tab. 2: Ratio Cw /Cw;FEM depending on Ast and Ist.

Ast

Ist

→

0

[mm4]

5

[mm4]

10

[mm4]

20

[mm4]

50

[mm4]

100

[mm4]

0 [mm2] 0.984 0.986 0.986 0.985 0.981 0.969

5 [mm2] 0.986 0.988 0.988 0.987 0.982 0.970

10 [mm2] 0.988 0.989 0.989 0.988 0.983 0.972

20 [mm2] 0.992 0.993 0.993 0.991 0.985 0.975

50 [mm2] 1.003 1.003 1.001 0.999 0.991 0.981

100 [mm2] 1.012 1.011 1.010 1.006 0.997 0.986

Fig. 4: Variation of Cw;FEM depending on Ist.

It can also be concluded that the calculation of the post-buckling behavior is more sensitive to inaccuracies in the assumed deflection shape than that of the buckling stress and that a two term approximation of the buckled shape is needed.

Figure 5 shows a comparison of the analytically and numerically determined load-deflection curves for plates with various stiffener properties. It can be seen that the two-strip model gives good results, also for plates with imperfections different from 0.005t, for which E*/E was determined. More research is needed to see if the model may be extended to determine failure loads of rectangular plates with one or more stiffeners.

Fig. 5: Load-deflection curves (analytically) determined by theory (T) and by ANSYS simulations (FEM).

Acknowledgements

Works were supported by funds of the conceptual development of science, research and innovations granted to VŠB-TUO by the Ministry of Education, Youth and Sports of the CR.

References

[1] Rhodes, J. Effective widths in plate buckling. In: Rhodes J., Walker AC., editors. Developments in Thin-Walled Structures-1, London, England: Applied Science Publishers, p. 119-158. 1982.

[2] Bakker, M.C.M., Rosmanit, M. and Hofmeyer, H. Elastic post-buckling analysis of compressed plates using a two-strip model. Thin Walled Structures, Vol. 45, Issue 5, p. 502-516, 2007.

[3] Rosmanit, M. and Bakker, M.C.M. Report on two-strip model for elastic post-buckling behaviour of plates with one central intermediate stiffener, Research Report O-2007.14, TUE, Department of Architecture, Building and Planning, Structural Design Group, The Netherlands, 2007.

[4] Timoshenko, S.P. and Gere, J.M. Theory of elastic stability, 2nd ed. New York: McGraw-Hill, 1963.

0.80

0.85

0.90

0.95

1.00

0 20 40 60 80 100I st [mm4]

C w;FEM

A st = 100 mm2

A st = 20 mm2

A st = 0 mm2

0.0

0.4

0.8

1.2

1.6

0.0 0.5 1.0 1.5 2.0 2.5w max/t

A st = 100 mm2

I st = 0 mm4

I st = 20 mm4

I st = 100 mm4

I st = 0 mm4

I st = 20 mm4

I st = 100 mm4

w 0 = 0.005t

w 0 = 0.25t

F /F cr

T

FEM

T

FEM

T

FEM

T

FEMT

FEM

T

FEM

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REAL BEHAVIOR OF END-PLATE BOLT CONNECTIONS OF TENSIONED PROFILES

Miroslav ROSMANIT1, Anežka MACHALOVÁ2

1Department of Structures, Faculty of Civil Engineering, University, VSB – TU Ostrava, L. Podeste 1875, Ostrava, Czech Republic

2Computer Technology Unit, Faculty of Civil Engineering, University, VSB – TU Ostrava, L. Podeste 1875, Ostrava, Czech Republic


Abstract. Real behavior of end-plate connections of angle profiles and of CHS (Circular Hollow Section) in tension was studied experimentally and numerically. Two different end-plate thicknesses and consequently different failure modes were researched. Comparison of results, in the form of load-deformation curves, showed that advanced numerical models describe the basic behavior of those joints. This study was also extended by testing of steel samples for creating the real material models in the form of multilinear stress-strain diagrams. Final diagrams were then used in numerical models of researched joints. The results obtained from numerical models were compared with the experimental results and also with the analytical solution of such joints. Used procedures are similar to principles mentioned in EN 1993-1-8. This paper contains recommendations for creation of the FEM models using real material properties, for their comparison with real laboratory tests and for calculation of load-bearing capacity of these joints.

Keywords

End-plate connection, bolts in tension, prying forces, numerical solution, FEM, real material properties.

1. Introduction

The lattice girders or truss frames made of either hollow or open cross sections are often used for large span structures. However, it is necessary to ensure proper assembling connection of individual components, for which the end-plate bolt joints are often used. Proper design of joints is an integral part of the designing of structures and is important for economy and service life of buildings. Therefore, the development of design methods

of joints is important for sustainable development in the construction industry.

End-plate bolt connections, if under tensile stress, should be designed taking into account also the possible influence of prying. Design methods given by Eurocode3 procedure are complicated and for some types of joints are not even exactly described. Behavior of connections using equivalent T-stub flange in tension theory which allows predicting the influence of prying is still actual and many of the world research teams are dealing with that [1 – 4].

Fig. 1: Scheme of the specimen of angle profile joints and geometry [mm] of the specimen.

Fig. 2: Scheme of the specimen of CHS joints and geometry [mm] of the specimen.


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2. Laboratory tests and FEM

During the laboratory tests the values of applied axial force and the overall vertical displacement were recorded from the test press. Two different thicknesses of the end-plate (10 and 15 mm) were tested in both connections. For the connection with 15 mm end-plates the rupture of bolts should have been the decisive failure mode. For joint with 10 mm end-plate the development of significant deformations of the plates (prying) was expected as the effect of plastification, hence the measurement using strain gauges at selected locations was also performed. The achievement of plastic deformations in the end-plates was confirmed inter alia by the fact that the measuring capacity of strain gauges had been exceeded.

2.1. Determination of real material properties

From each material (10 mm plate, 15 mm plate and profile L 90x10) three pieces of material samples were manufactured (Figure 3). The tensile tests were then performed with these samples from which load-deformation curves of each sample were obtained. Based on the comparison of the load-deformation curves from the press and those from numerical models, suitable stress-strain diagrams of the individual materials were searched. These material models were then used for numerical modelling of the entire joints.

Numerical models of material samples were created in the FEM software ANSYS 12.0. CP algorithm was used for boundary conditions to simulate the fastening of the sample in the press (Figure 3). Afterwards the load was applied on one of the main nodes in the form of prescribed axial deformation uy (according to Figure 3). Behavior of materials was expressed by multilinear stress-strain diagrams, which were gradually modified to achieve the best possible conformity between the load-deformation curves obtained from FEM and from the tensile tests.

Fig. 3: a) Boundary conditions of the numerical model (including the coordinate axes). b) Detail of the real sample with noticeable notches caused by the jaws of the press.

2.2. Connection of the angle profiles

The researched assembling joints connected two angle profiles L 90x10 and consisted of two rectangular end-plates (185x130 mm) with thicknesses tf,1 = 10 mm and tf,2 = 15 mm, fastened together by M16 bolts grade 8.8. These thicknesses of the end-plates have been chosen so as to achieve different failure modes of the joints.

The geometry of tested connections was significantly influenced by parameters of an available trial press machine. Figure 1 shows the scheme of prepared specimens which were tested. The end-plates were made of the S355 steel and the L-profile was made of the S235 steel.

Numerical models of researched joint (Figure 4a) were created in the FEM software ANSYS 12.0 using the finite elements enabling non-linear calculations (both plastic behavior of materials and large displacement static). The end-plates have been modeled at a distance of 1 mm (as a simplification of the initial imperfections). The load was transmitted into the joint through the beam element which simulated welded threaded rod (similarly to the real experimental set-up) in the form of prescribed axial deformation. For the mutual connection of this beam elements and elements representing the L-profiles the MPC algorithm was used (as in [4]).

Fig. 4: Numerical model of researched joints with FE mesh and boundary conditions: a) angle profiles; b) CHS profiles.

Typical material properties were assigned to the finite elements - Young’s modulus of elasticity E = 210 GPa and Poisson’s ratio ν = 0.3. Both physical and geometrical non-linear aspects were considered within the calculation (plastic behavior considering the large deformations), while the elasto-plastic behavior of materials was expressed by multilinear material models. Newton-Raphson method was used for solution of nonlinear equations of system.

Stress-strain diagrams of material properties of steel plates and L-profiles were based on performed tensile tests of material samples. The tensile tests of used bolts were not performed, therefore the material properties of bolts were taken from available literature, concretely recommenda-tions according to Swanson’s labour [5] were used.

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2.3. Connection of the CHS profiles

The researched assembling joints connected two CHS profiles TR 89x8 and consisted of two circular end-plates with diameter of 230 mm, with thicknesses tf,1 = 10 mm and tf,2 = 15 mm, fastened together by M16 bolts grade 8.8. These thicknesses of the end-plates have been chosen so as to achieve different failure modes of the joints.

The geometry of tested connections was significantly influenced by parameters of an available trial press machine. Figure 2 shows the scheme of prepared specimens which were tested. Both the end-plates were and the CHS profile were made of the steel S235.

For the connection with 15 mm end-plates significant plastification of plates was not expected, therefore the rupture of bolts should be the decisive failure mode. The main objective of this test was to indicate the overall behavior of tested joint and suitability of the proposed fastening in the press. During this test, an unexpected rupture of the threaded rod (element used for transmission of the load into the joint) had occurred, but results from the beginning of the test (up to the axial force 320 kN) could have been used.

For joint with 10 mm end-plate the development of significant deformations of the plates (prying) was expected as the effect of plastification, hence the measurement using strain gauges at selected locations was also performed. The achievement of plastic deformations in the end-plates was confirmed inter alia by the fact that the measuring capacity of strain gauges had been exceeded.

Numerical models of researched joint (Figure 4b) were created in the FEM software ANSYS 12.0. Similar methods were used while creating the model. Both numerical models were simplified in many ways, for example the connections between the bolts and nuts and then between the nuts and plates were modelled as a rigid, which does not exactly match the real situation, but is sufficient for capturing the behavior of the joint.

3. Conclusion

The numerical models of end-plate assembling bolt connections of angle and CHS profiles with the end-plate thicknesses of 10 mm and 15 mm were created in FEM program ANSYS 12.0. These joints were also tested in the laboratory of the Faculty of Civil Engineering, VSB - TUO. The comparison of experimental and numerical load-deformation curves or the comparison of deformed shapes of particular joints showed that the numerical models describe the basic behavior of these joints.

The original numerical model outputs were modified with respect to real laboratory conditions by taking into account the slip stiffness of the trial press machine and the initial slip. The comparison of experimental curve with both modified numerical model outputs (curve "ANSYS with

the slip stiffness"), and not modified results (curve "ANSYS without the slip stiffness") expressing the stiffness of joints themselves was made. These original outputs were compared with the part of the experimental curve during unloading and reloading, which presents the real stiffness of the specimen itself, without the influence of test press stiffness. From the comparison it is evident that the stiffness of the numerical model and the real sample coincide. It can be concluded that designing of the nonsymmetrical connections is inappropriate, due to the uncertain distribution of internal forces in the individual components of joint. The specific distribution of internal forces depends partly on the geometry of the connection and especially on the stiffness of each component of the joint, which is not easy to express analytically.

Performing other experiments with a higher number of specimens is assumed for further research. The aim of the entire research is a suggestion of possible modifications of existing analytical relations that are listed in the Eurocode3 and are not generally applicable.

Acknowledgements


References

[1] Cao J. J. and Bell A. J.: Determination of bolt forces in a circular flange joint under tension force International Journal of Pressure Vessels and Piping 68 (1) p. 63-71 DOI: 10.1016/0308-0161(95) 00040-2. ISSN 03080161, 1996.

[2] Hantouche E. G., Rassati G. A., Kukreti A. R. and Swanson J. A.: Built-up T-stub connections for moment resisting frames: Experimental and finite element investigation for prequalification Engineering Structures 43 p. 139-148 ISSN 0141-0296, 2012.

[3] Jaspart J. P., Pietrapertosa C., Weynand K., Busse E. and Klinkhammer R.: Development of a full consistent design approach for bolted and welded joints in building frames and trusses between steel members made of hollow and/or open sections: application of the component method. Volume 1: practical guidelines. CIDECT Report 5BP – 4/05, 2005.

[4] Jurčíková A. and Rosmanit M.: Recommendations for numerical modeling and analytical assessment of a planar steel CHS joint Transactions of the VŠB - Technical University of Ostrava, Civil Engineering Series Versita XIII (2) p. 10 ISSN 1804-4824, 2013.

[5] Swanson J. A., Kokan D. S. and Leon R. T.: Advanced finite element modeling of bolted T-stub connection components Journal of Constructional Steel Research 58 p. 1015-1031, ISSN 0143-974X., 2012.

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LOAD-CARRYING CAPACITY OF BOLTED CONNECTIONS OF ROUND TIMBER WITH DIFFERENT DISTANCES BETWEEN THE

FASTENER AND THE LOADED END

Pavel DOBEŠ1, Antonín LOKAJ1

1Department of Structures, Faculty of Civil Engineering, VSB Technical University of Ostrava, Ludvíka Podéště 1875/17, Ostrava, Czech Republic


Abstract. The paper deals with the results of static tests of bolted connections of round timber with inserted steel plates. Fifteen specimens of three different distances between the fastener and the loaded end were subjected to tension parallel to the grain and the load-deformation diagram of the connections was recorded. The test results were statistically evaluated, complemented with records of the load-deformation curves and compared with the calculation according to the valid standard for design of timber structures.

Keywords

Bolt, connection, round timber, steel plate, structure, test.

1. Introduction

When designing timber structures, the key issue is the design of their connections as they have a major influence on the serviceability and durability of the whole structure. The most common types of connections used in timber structures are connections with metal mechanical fasteners and steel plates inserted into cutouts of timber members (for more see [5], [6], [7], [8], [9], [10], [11], [12]).

The European standard for the design of timber structures [1] deals with timber-to-timber or steel-to-timber connections using mechanical fasteners (bolts, dowels, nails, screws, etc.). The calculation of the load-carrying capacity of connections does not take into account the edge and end distances and spacings for fasteners, which are only given as the minimum recommended values. Therefore, static tests of bolted connections of round timber with inserted steel plates were carried out. Three variants of connections with different distances between the fastener and the loaded end were

loaded by tension parallel to the grain (until failure) in order to prove if the real load-carrying capacity is influenced by the distance.

2. Methods of Testing

2.1. Description of Materials for Test Specimens

Specimens for tension tests parallel to the grain were made of twice half-round of 60 mm diameter. They were made of spruce timber of C24 strength class. Specimens of three different lengths were tested (see Fig. 1) - 400 mm (designation K1), 480 mm (designation K2), 560 mm (designation K3). The circular holes in the timber members for placement of fasteners had a diameter of 20 mm.

High tensile bolts grade 8.8 (fy = 640 MPa, fu = 800 MPa) with a diameter of 20 mm were used as fasteners. The bolts were placed at three different distances from the loaded end – 140 mm (= 7x bolt diameter), 180 mm (= 9x bolt diameter), 220 mm (= 11x bolt diameter). The axial spacing between two bolts in one specimen was 120 mm.

The steel plates were made of structural steel grade S235J0 with thickness of 10 mm. Dimensions of the steel plates also varied depending on the distance between the fastener and the loaded end. The protruding part of the plates for clamping the plates into the jaws of the testing machine was 180 mm long. The plates had circular holes with a diameter of 22 mm for placing bolts (a clearance of 2 mm was left).



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Fig. 1: Types of specimens for parallel to the grain tension test.

2.2. Description of the Course of the Testing

Several non-destructive tests were carried out before the main testing to determine the density [2] and the moisture content [3] of used timber. The test specimens were then clamped into the jaws of the testing machine so that the tested connection was subjected to an axial tensile load with possible additional effects from imperfections (see Fig 2).

During the test, continuous recording of the time, the tensile force and the deformation of the connection in the longitudinal direction was performed. The course of loading was carried out according to the standard for the testing of connections of timber structures with mechanical fasteners [4], that states this procedure:

1. Estimation of the maximum force Fest for the tested connection based on experience, calculation or pre-tests.

2. Loading of the specimen to the level of 40% of the estimated maximum force 0.4·Fest, then waiting on that level of the load for 30 seconds.

3. Decrease of the loading to the level of 10% of the estimated maximum force 0.1·Fest, then waiting on that level of the load for 30 seconds.

4. Continuous loading to failure of the specimen (see Fig. 3).

The loading speed was chosen constant in mm/min or kN/min. The total testing time of one specimen was about 10 to 15 minutes.

Fig. 2: A specimen clamped into the jaws of the testing machine.

Fig. 3: A specimen after failure.

3. Results

Three types of bolt connections of round timber with inserted steel plates were tested for this paper (five specimens for each type). Tab. 1, 2, 3 show statistically evaluated values of bulk density and moisture content of used timber and maximum failure forces for all the types (K1, K2, K3). Fig. 4 shows the load-deformation curves of the K2 specimens.

According to Eurocode 5 [1], it is considered a double shear steel-to-timber connection (for a steel plate of any thickness as a central member). The characteristic load-carrying capacity without the contribution from the rope effect of the given types of the connections is

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Fv,Rk = 46528 N (input values for timber of C24 strength class and bolt M20 grade 8.8 were used in the calculation). Tab. 1: Values of bulk density, moisture content a maximum force at

failure for K1.

K1

ρ [kg/m3] w [%] Fmax [N]

Bulk density Moisture content

Maximum force at failure

Average 458 13.2 69979

Sample standard deviation

74.7 0.6 8042

Coefficient of variation

16.30% 4.25% 11.49%

5% quantile value 274 - 50196

Tab. 2: Values of bulk density, moisture content a maximum force at failure for K2.

K2




Average 455 12.8 85808


61.2 0.8 10738


13.47% 5.89% 12.51%


Tab. 3: Values of bulk density, moisture content a maximum force at failure for K3.

K3




Average 431 12.8 81622


35.2 0.5 5275


8.15% 3.69% 6.46%


Fig. 4: Load-deformation curves for K2 specimens

4. Discussion of the Results

From the beginning of loading, plastic deformation of holes in timber members increased until the failure of the tested specimens caused by tension perpendicular to the grain (splitting of individual fibers in timber under the bolt). This is due to the fact that the timber in tension has little plasticity and is broken by a brittle fracture.

As can be seen in Fig. 4, the specimens with the most significant initial slip were broken at the lowest force (specimens K2-3 and K2-5). Probably, the timber had exhausted all its plasticity in the compression during the initial phase of loading, and in the final phase a brittle tensile failure soon occurred. Whereas, the specimen with the least significant initial slip shows a considerable plasticity in the final phase of loading (specimen K2-1).

Tab. 1, 2, 3 show that the average value of maximum force at failure is lowest for the shortest distance between the fastener and the loaded end (ie 7d). For specimens with higher distances (ie 9d and 11d), the average values of load-carrying capacity are higher, with the highest value for the middle length specimens (K2 specimens).

For construction practice, the decisive values are the characteristic values (5% quantile values). The characteristic load-carrying capacity values for all types of specimens are higher than the standard value for the double shear steel-to-timber connection (for a steel plate of any thickness as the central member of a double shear connection). The highest characteristic value was evaluated for K3 specimens (the longest distance between the fastener and the loaded end). However, it is not possible to draw a definitive conclusion that there is a significant influence of the distance between the fastener and the loaded end on the characteristic load-carrying capacity of real connections. This is complicated by the small amount of tested specimens, which considerably affects the statistical evaluation of specimens with higher coefficient of variation.

5. Conclusion

Experimental tests of bolted connections of round timber with inserted steel plates of different distances between the fastener and the loaded end were performed. For a more objective, more comprehensive conclusion about the behavior of these connections and the verification of the tests already done, it is necessary to carry out another series of tests in the coming period.

Connections with inserted steel plates are also widely used in exterior timber structures that are subjected to significant temperature and moisture content changes and which are predominantly loaded by wind having the characteristics of an alternating dynamic load. The future research of this issue should focus on cyclic, dynamic tests and tests using specimens with different moisture content of timber members.

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Acknowledgements

This paper has been achieved with the financial support of the Ministry of Education, specifically by the Student Research Grant Competition of the Technical University of Ostrava in 2020.

References

[1] EN 1995-1-1. Eurocode 5: Design of timber structures – Part 1-1: General – Common rules and rules for buildings. Praha: Czech Standards Institute, 2006.

[2] EN 384+A1. Structural timber - Determination of characteristic values of mechanical properties and density. Praha: Czech Office for Standards, Metrology and Testing, 2019.

[3] EN 13183-2. Moisture content of a piece of sawn timber - Part 2: Estimation by electrical resistance method. Praha: Czech Standards Institute, 2002.

[4] EN 26891. Timber structures. Joints made with mechanical fasteners. General principles for the determination of strength and deformation characteristics. Praha: Czech Standards Institute, 1994.

[5] BLA, H. J. and C. SANDHAAS. Timber engineering – Principles for desing. Karlsruhe: Karlsruher Institut für Technologie, 2017. ISBN 978-3-7315-0673-7.

[6] THELANDERSSON, S. and H. J. LARSEN, ed. Timber engineering. Chichester: Wiley, 2003. ISBN 0-470-84469-8.

[7] FOJTÍK, R., A. LOKAJ and J. GABRIEL. Timber bridges and footbridges. Praha: CKAIT Information center, 2017. ISBN 978-80-88265-04-7.

[8] JOHANSEN, K. W. Theory of timber connections. International Association of Bridge and Structural Engineering. Bern, 1949.

[9] BLA, H. J. and P. SCHÄDLE, P. Ductility aspects of reinforced and non-reinforced joints. Engineering Structures. 2011, vol. 33, iss. 11, pp. 3018-3026. ISSN 0141-0296.

[10] JORISSEN, A. J. M. Double shear timber connections with dowel type fasteners. PhD thesis. Delft: TU Delft, 1998. ISBN 90-407-1783-4.

[11] SANDHAAS, C. Mechanical Behaviour of Timber Joints with Slotted-in Steel Plates. PhD thesis. Delft: TU Delft, 2012. ISBN 978-90-8570-837-7.

[12] LOKAJ, A., K. KLAJMONOVÁ, D. MIKOLÁŠEK and K. VAVRUŠOVÁ. Round timber bolted joints exposed to static and dynamic loading. Wood Research. 2014, vol. 59, iss. 3, pp. 439-448, ISSN 13364561.

[13] DOBEŠ, P., A. LOKAJ, L. PONIŠTOVÁ and R. PAPESCH. Bending stiffness of selected types of glued I-beams made of wood based materials. ARPN Journal of Engineering and Applied Sciences. 2019, vol. 14, iss. 7, pp. 1357-1361. ISSN 18196608.

[14] DOBEŠ, P., A. LOKAJ and Oldřich SUCHARDA. Test results of connections of timber structures. In: Proceedings of 204th IASTEM International Conference. Amsterdam, 2019, vol. 204, pp. 1-4.

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DESIGN OF STRUCTURAL ELEMENTS MADE OF NEW VARIANTS OF CONCRETE WITH REGARD TO SUSTAINABILITY

Pavlina MATECKOVA1, Oldrich SUCHARDA2, Vlastimil BÍLEK2, Lucie MYNARZOVA1

1Department of Structures, Faculty of Civil Engineering, VSB – TU Ostrava, L. Podeste 1875, Ostrava, Czech Republic

2Department of Building Materials and Diagnostics of Structures, Faculty of Civil Engineering, VSB – TU Ostrava, L. Podeste 1875, Ostrava, Czech Republic


Abstract. Current actual criteria in structural design is also decreasing of CO2 emission together with increasing durability and service life. The paper deals with design of structural elements made of newly developed variants of concrete/composite mixture, specifically high strength concrete for pre-tensioned beams, high performance concrete with increased durability and chlorides penetration resistance, alkali activated composite and fibre high strength concrete. Listed materials are based on common and available raw materials and production of structural elements is verified in specific industrial conditions in the company which produces precast concrete. Utilization of newly developed materials variants in structural design bring forth issues connected with safety and reliability when compared with traditional concrete. Precast elements made of newly developed concrete were tested in experimental centre. Loading test results were compared with the load capacity calculated according to current codes and load capacity determined on the basis of non-linear numerical model of structural element exposed to mechanical load.

Keywords

Load bearing test, high strength concrete, alkali activated composite, fibre concrete.

1. Introduction

Sustainability in civil engineering is connected closely with utilization of new materials or innovation and improvement of traditional materials. Concrete as a traditional material for load bearing structures abounds with innovative variant, such as fibre concrete, self compacting concrete and also high strength concrete with the strength over 100 MPa [1]. New variants of concrete were analysed from the point of view of convenient concrete mixture and technology of fresh concrete, as well

as increased load capacity, durability and fatigue parameters [2].

2. Material Variants

2.1. High Strength Concrete for Pre-tensioned Beams

High strength concrete mixture is designed primarily for modular series of pre-tensioned concrete bridge beams, Fig. 1. Particular important design criteria was optimization of concrete technology in specific industrial conditions. i.e. requirements for consistency and transport of fresh concrete, treatment, required strength for removing formwork and time of pre-stressing activation. It is also necessary to take into consideration shrinkage and creep. It was proved that new variant of high strength concrete possess increased chlorides penetration resistance, which is important especially for bridge structures [3].

Fig. 1: Pre-tensioned beam after load bearing test.

2.2. High performance concrete High performance concrete is designed primarily for reinforced concrete beams and girders, Fig.2, in industrial but also in common civil engineering where there are



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requirements for aggressive environment resistivity. Designed concrete mixture respects availability of raw materials and its utilization was proved in specific industrial conditions where speeding up of precast concrete technology is possible due to fact that design mixture fulfils criteria for self-compacting concrete.

Fig. 2: High performance reinforced concrete beam after load bearing test.

2.3. High Strength Fibre Concrete Beams with I shaped cross-section were made from high strength concrete with fibres, Fig. 3. Two types of fibres were used in concrete mixture, short straight fibres together with 3D fibres. The aim was to decrease amount of shear reinforcement and thus save steel material and overall weight. Increased durability and aggressive environment resistivity as well as increased ductility were obvious design criteria.

Fig. 3: I beam made of high strength fibre concrete after load bearing test.

2.4. Alcali Activated Composite

In this variant of concrete cement is replaced with milled slag. Chemical reaction is activated with potassium hydroxide. Energy consumption and CO2 emission for produce of this composite variant is lower when compared with commonly used concrete mixture and utilization of this variant of composite could contribute to environment protection and sustainability in civil engineering. Series of reinforced concrete composite beams was made in industrial conditions, Fig. 4, and utilization of this type of composite in structural elements is still unique.

Fig. 4: Reinforced beam made of alkali activated composite during load bearing test.

3. Conclusion

In the paper four new variants of concrete and composite are presented. Material variants were developed with the aim to increase load capacity and serviceability of designed structural elements and decrease effect on the environment at the same time. Emphasis was laid on the availability of raw materials and verification of utilization in industrial conditions. A few of reinforced or pre-stressed concrete beams elements were made of all four variants of concrete and exposed to load capacity test in experimental centre. Appropriate material variant choice depends on type of structural beam, expected load and its emplacement.

Acknowledgements


References

[1] PONIKIEWSKI, T. and J. KATZER. Mechanical properties and fibre density of steel fibre reinforced self-compacting concrete slabs by DIA and XCT approaches, Journal of Civil Engineering and Management. 2017, vol. 23, iss. 5. ISSN 604-612. doi.org/10.3846/13923730.2016.1217922

[2] MIARKA, P., S. SEITL and V. BILEK. Mixed-mode fracture analysis in high-performance concrete using a brazilian disc test, Materiali in Tehnologije. 2019, vol. 53, iss 2. ISSN 15802949 doi:10.17222/mit.2018.161

[3] KONEČNÝ, P., P. LEHNER and D. PUSTKA. Reinforced concrete bridge deck model considering delayed exposure to chlorides, Periodica Polytechnica Civil Engineering. 2019, vol. 63, iss. 3. ISSN 05536626 doi:10.3311/PPci.13780

https://doi.org/10.3846/13923730.2016.1217922

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EXPERIMENTAL TESTING OF POST-TENSIONED INDUSTRIAL FLOOR MODELS

Petr MYNARCIK1, Jiri KOKTAN1, Ondrej MILLER2,

1Centre of Building Experiments, Faculty of Civil Engineering, VSB Technical University of Ostrava, LudvikaPodeste 1875/17, Ostrava, Czech Republic

2Department of Structures, Faculty of Civil Engineering, VSB Technical University of Ostrava, LudvikaPodeste 1875/17, Ostrava, Czech Republic


Abstract. The article presents comparison between three different models of post-tensioned industrial floors. Models were realised in large scale dimensions and tested with centric static load device. The experimental models were designed with different content of steel fiber reinforcement. Presented static load tests were part of a series of experiments focused on problematic of interaction between concrete structures and subsoil and was realized at the Faculty of Civil Engineering, VŠB –Technical university of Ostrava.

Keywords

Post-tensioned concrete, Industrial floor, fiber-reinforced concrete, interaction between foundation slab and subsoil.

1. Introduction

Experimental tests were designed like a model situation of interaction between concrete column, concrete slab-on-ground and subsoil. The experimental models were designed with different contents of steel fiber reinforcement. Sample overview with real content of fibres is displayed in Tab.1.

Tab. 1: Sample overview.

Code Description

PTS01 – WF Post-tensioned slab – without fibers

PTS02 – F40 Post-tensioned slab – steel fiber 40kg/m3

PTS03 – F60 Post-tensioned slab – steel fiber 60kg/m3

2. Experimental testing

Main part of experimental test was concrete slab model in large scale. This model had square plane shape with the basic dimension 2,0 x 2,0 m and with slab thickness 0,15 m. The fresh concrete with class of concrete C25/30 XF1 was delivered by commercial supplier of concrete. Six fully threaded prestressing threadbars were used for post-tensioning of experimental concrete slab model. The material of threadbars was from low relaxation steel with designation Y 1050 and diameters of these threadbars were 18 mm. The size of post-tensioning force for each threadbar was 100kN. Threadbars were prestressed with use of hydraulic hollow cylinder. Threadbars were anchored by domed nuts and recessed anchor plates. The experimental slab was based on homogeneous sand subsoil and situated in outdoor testing device STAND. The vertical load was caused by the high tonnage hydraulic cylinder. The loaded equipment was placed between the experimental model and the steel extension fixed on the testing device for experimental measurements of foundation slabs on the subsoil “STAND” The hydraulic system was equipped with the pressure sensor. The vertical load was caused by the high tonnage hydraulic cylinder ENERPAC CLRG. Potentiometric position sensors were installed on the surface of concrete floor model [1,2,3].

Vertical deformations were measured by the set of 16 potentiometers. Potentiometers were connected to the recording sensor station. The station was programmed to automatic scanning and recording measured values. Time interval for record of deformation measurement was 10 seconds. Schematic plan of sensors is displayed on Fig.2.




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Fig. 1: Post-tensioned industrial floor model - measurement and testing devices.

Fig. 2: Schematic plan of potentiometers.

Fig. 3: Subsidence line A-A´.

Fig. 4: Subsidence line B-B´.

3. Conclusion

Example of subsidence of experimental post-tensioned slab-on-ground model in line A-A´ is displayed in Fig.3. and subsidence of experimental post-tensioned slab-on-ground model in line B-B´ is displayed in Fig.4. This graphical investigation was realized for every tested model and compared.

Acknowledgements

This article has been achieved with the financial support of the Ministry of Education, specifically by the Student Research Grant Competition of the Technical University of Ostrava.

References

[1] SUCHARDA, O., SMIRAKOVA, M., VASKOVA, J., MATECKOVA, P., KUBOSEK, J., CAJKA, R. Punching Shear Failure of Concrete Ground Supported Slab. International Journal of Concrete Structures and Materials. 2018, vol. 12, art. no. 36. DOI: 10.1186/s40069-018-0263-6.

[2] CAJKA, R., MARCALIKOVA, Z., NEUWIRTHOVA, Z., MYNARCIK, P. Testing of FRC Foundation Slab Under Eccentric Load. Proceedings of the fib Symposium 2019: Concrete – Innovations in Materials, Design and Structures, 2019, pp.380-386.

[3] HRUBESOVA, E., MOHYLA, M., LAHUTA, H., BUI, T.Q., NGUYEN, P.D. Experimental analysis of stresses in subsoil below a rectangular fiber concrete slab. Sustainability. 2018, vol. 10, art. no. 2216. DOI: 10.3390/su10072216.

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ANALYSIS AND EXPERIMENTAL TESTING OF FIBRE REINFORCEMENT CONCRETE SLABS IN INTERACTION WITH

SUBSOIL

Radim CAJKA1, Marie KOZIELOVA1, Zuzana MARCALIKOVA1, Pavlina MATECKOVA1, Oldrich SUCHARDA2

1Department of Structures, Faculty of Civil Engineering, VSB-Technical University Ostrava, Ludvíka Podéště 1875/17, 708 00 Ostrava - Poruba, Czech Republic

2Department of Building Materials and Diagnostics of Structures, Faculty of Civil Engineering, VSB-Technical University Ostrava, Ludvíka Podéště 1875/17, 708 00 Ostrava - Poruba, Czech Republic

[email protected], [email protected], [email protected], [email protected], [email protected]

Abstract. The article is focused on composite material which can contribute to sustainability by its suitable design application. The research is specifically focused on reinforced concrete and its application at the slab near the subsoil. The experimental series deals in details fibre use at the rate from 0 to 75 kg/m3. The research is based on a comparison of a comprehensive experimental program and advanced numerical modelling taking into account real behaviour. The main experimental program tests four reinforced concrete slabs on a specialized device. Part of the experiment was to perform laboratory tests and to identify the mechanical properties of concrete for nonlinear analysis. The tests were compressive tests, modulus of elasticity, transverse tensile strength, flexural tensile strength, and specialized tests determining fracture energy. The information about the mechanical properties of concrete and subsoil were then used for numerical simulation of a 3D computational model, where the results were compared with experimental measuring. Among the main benefits brought by the results is the fact that we managed to computationally create a realistic simulation of slab behaviour, which was supplemented with a complex description of mechanical properties of the material.

Keywords

Fibres, reinforced concrete, slab, subsoil, experiment, numerical modelling, mechanical properties, analysis, nonlinear calculation.

1. Introduction

Four slabs of the dimensions 2000x2000x150 mm were experimentally tested on a specialized device, see fig. 1. The slabs were from concrete and contained scattered fibre reinforcement 0, 25, 50, 75 kg/m3.

Fig. 1: Loading test.

All slabs were poured onto the same subsoil, which was modified before the cementing process itself and before experimental measuring. The subsoil was categorized on the basis of geotechnical research as CI - clay with medium plasticity. The experimental measuring was based on the gradual loading of the concrete slab using a hydraulic press. The load took place in steps. For plain concrete slab (0 kg/m3 fibre) load steps were set at 25 kN/30 min. Fibre admixture slab (25, 50, 75 kg/m3) had a load step of 75 kN/ 30 min. All slabs were loaded until their load-bearing capacity was reached. The time course of loading is shown on fig. 2. Part of the experimental tests of concrete slabs





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was the performing of laboratory tests for determining mechanical properties of concrete, where these properties are necessary for numerical modelling as input parameters

Fig. 2: Time course of load in experimental testing.

A comparison with the numerical 3D model, which assumes nonlinear behaviour of material is also included in the paper. Fig. 3 shows displacement for the numerical model of the slab with fibre admixture. The deformations correspond to a load of 150 kN (min. 0.2 mm crack).

Fig. 3: 3D Numerical analysis output, crack and displacement, slab G01, load 150 kN (min. crack 0.2 mm).

2. Conclusion

The article presents an integrated research program which focused on the option to use fibre concrete for the specific task of foundation slab. Experimental program included the complete series of four in situ tests – slabs in interaction with the subsoil on a special testing facility, and a laboratory program defining mechanical properties of concrete and fibre concrete. Fibre concrete was gauged specifically in the ratio of 25, 50, 75 kg/m3. The extensive set of results of laboratory tests was then used for input data of material models in nonlinear analysis of slabs in interaction with the subsoil. The results of the numerical simulations are very close to the results of performed experiments; differences between experiments and numerical calculations may be considered small.

Acknowledgements

Works have been supported by funds of the conceptual development of science, research and innovations granted to VŠB-TUO by the Ministry of Education, Youth and Sports of the CR.

References

[1] ABOUTALEBI, M. ALANI, A. RIZZUTO, J. and D. BECKETT. Structural behaviour and deformation patterns in loaded plain concrete ground-supported slabs. Structural Concrete. 2014, vol. 15, iss. 1, pp. 81-93. DOI:10.1002/suco.201300043.

[2] SIBURG C. and J. HEGGER. Experimental investigations on the punching behaviour of reinforced concrete footings with structural dimensions, Structural Concrete. 2014, vol. 15, iss. 3. DOI: 10.1002/suco.201300083

[3] HALVONIK, J. HANZEL, J. and L. MAJTANOVA. Punching Resistance of Column Basis. Advances and Trends in Engineering Sciences and Technologies II. In: 2nd International Conference on Engineering Sciences and Technologies (ESaT), pp. 93-98, 2017.

[4] HEGGER, J. SHERIF, G., A. and M. RICKER. Experimental Investigations on Punching Behaviour of Reinforced Concrete Footings. ACI Structural Journal, 2006, pp. 604-613.

[5] CSN EN 1992-1-1, Eurocode 2: Design of concrete structures - Part 1-1: General rules and rules for buildings, 2006.

[6] CAJKA, R. Comparison of the calculated and experimentally measured values of settlement and stress state of concrete slab on subsoil. Applied Mechanics and Materials, vol. 501-504, pp. 867-876. Trans Tech Publications, Switzerland, DOI:10.4028/www.scientific.net/AMM.501-504.867.

[7] Dramix® steel fiber concrete reinforcement - Bekaert.com, https://www.bekaert.com.

http://www.scientific.net/AMM.501-504.867#_blank

http://www.scientific.net/AMM.501-504.867#_blank

https://www.bekaert.com/

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USING 3D SCAN FOR STEEL STRUCTURE SURVEYS

Tomas NOVOTNY1

1Department of Structures, Faculty of Civil Engineering, VSB-Technical University of Ostrava,

17. listopadu 2172/15, Ostrava, Czech Republic

[email protected]

Abstract. Laser 3D scan is a longer time known

technology, however its massive spreading happened just

recently due to decreasing prices of necessary equipment.

The practical use of the 3D laser scan needs to face

problems of tremendous amount of generated data that

must be further processed. Wide variety of commercial

software exists for processing of scans of buildings, statues

etc. However, steel structures are specific due to their

complex shapes and the commercial potential is limited to

the smaller amount specialists who deal with them

specifically. Therefore, the commercial software is not

suitable for usage and it was decided to develop specific

tools for the processing of 3D scans of steel structures. The

paper presents especially the evaluation of chimney

inclination among other tasks.

Keywords

3D scan, brownfield, laser scan, least square method,

steel structure.

1. Brownfield

The Czech Republic is a traditional industrial country

which has both positive and negative effects. The positive

ones are mainly rich industrial history with many

extremely interesting industrial plants, many of them being

changed into tourist attractions, e. g. famous “Lower Area Vitkovice” in Ostrava. However, the negative effects are also present: due to long lasting history and traditions,

many of the industrial technologies became obsolete,

enterprises bankrupted and former workshops are

deserted. The pace of change increased especially recently

due to rapid technological evolution, so called Industry 4.0

[1]. Many old plants are being closed down while many

new ones are arising. Most of the new plants are built in

the fields outside towns (greenfield), which is

understandable as the land prices are lower outside towns

and it is difficult to meet nowadays strict legal

requirements on noise, pollution and traffic within towns.

However, this causes not only the agricultural land area

decrease, but also the towns to be surrounded by gradually

collapsing deserted “old” industry, outside of which is the circle of the new one. The answer is to recycle the old

plants for new purposes whenever it is possible –

especially in industrial centres like Ostrava [2] is, so called

brownfield.

2. Mapping the Existing Buildings

and Structures

In some cases the old buildings including their structures

are completely dismantled and replaced by new buildings.

However, whenever possible it is preferred to preserve at

least partially the old buildings and structures, not only

from the economical reasons, but also in order to protect

our history, genius loci. Preserving the old is a hard task as

it requires many compromises and modifications. The first

step in preserving is always the survey how the original

building or structure looks like and how well it is

preserved.

In theory, each building and structure owner has duty

to preserve the original documentation, drawings and static

calculations. However, especially in industrial sphere, due

to the Czech wild economical transforms in nineties, the

documentation is lost quite often. The last hit was caused

by floods, as factory archives are often placed in cellars

and other low places. So in reality, many plants have lost

their documentation completely or partially. Before any

reconstruction starts, it is in each case necessary to search

at least fragments of original documentation in archives

and other places, however, it is necessary to be prepared to

measure the building or structure to obtain direct

information how does it look like.

Besides classical measurement, it is also necessary to

obtain information about the state of building or structure,

in the case of steel structures it is prescribed by Czech code


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CSN 73 2604 [3]. The most common way to obtain

required information is the classical measurement, besides

it is possible to use more sophisticated ways. One of them

is the 3D laser scan discussed in this paper.

3. 3D Laser Scan of Steel Structures

Laser scan can be used to map the steel structure. The

advantages are clear, it is possible to make a very fast and

very detailed survey resulting in many millions of

measured points within several minutes. The principal

disadvantage is the amount of measured data. Classical

“hand” measurement leads to few measured data, however

the measured data are usually the exactly required output.

On the other hand, 3D scan leads to millions of unwanted

data points and it is necessary to spend long time in office

to find out the few required correct values among a heap

of points. So it is possible to say that the 3D scan shifts the

difficult (and time consuming) part of the measurement

from outside to the office.

Fig. 1: 3D scan (cloud of points) of a power plant boiler.

Fig. 2: 3D virtual model of power plant boiler steel structure.

There are several common tasks to be solved by 3D

scan [4]. One of them is to measure the existing buildings

or structures as a plain surrounding that should be avoided

during the design of new parts. This is equivalent to

modified collision check. Other task is to check

correspondence of virtual 3D model to the reality. And

finally, most complex of these tasks is to create a virtual

model of existing building, for illustration see figures 1

and 2. Especially in the case of steel structures the data

processing still requires big amount of manual work.

Moreover, the resulting 3D scan is so exact that it reveals

effects like beam deflection as the real structure is

deflected due to gravity, while drawing-modelled virtual

structure is typically straight without deflections. This lead

the author to an idea to employ the 3D scan to measure

beam deflection as another task, or to evaluate the

inclinations of chimneys and similar structures using 3D

scans.

4. The Chimney Inclination

Evaluation

A specialized software [5] (see also figure 3) has been

developed as a tool for semi-automatic evaluation of

inclination of vertical structures with circular cross-

section, like chimneys, silos, poles, towers and similar

structures. The measured data are horizontally sliced into

several groups. Each of them is fitted a circle using the

least square method [6], the centres of circles are plotted

to represent measured inclination.

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Fig. 3: Software tool for evaluation of circular cross-section structure

inclination.

The first version of software employed the classical

penalty function in the form

Σi (di – R)2 → minimum, (1)

where R is the radius of fitter circle and di is the distance

of measured point “i” from the circle centre. This however doesn’t have closed-form analytical solution and must be

solved by non-linear optimization. The software employed

a robust combination of Newton-Rhapson method with

simulated annealing [7], however still the optimization

sometimes got caught in the wrong valley leading to quasi-

optimal solution if the primary original estimate is too far

from the final solution.

The second version works with modified penalty

function in the form

Σi (di2 – R2)2 → minimum, (2)

which is analytically solvable therefore its solution is

much faster and more reliable without need to provide the

primary estimate values.

However, the higher power in penalty function has

drawbacks as well. It must be evaluated with higher

precision as values power four to be summed may result in

quite big values.

Besides, from the same reason the optimization is more

sensitive even to a small amount of false measurement

with large errors. The cure to this problem is to iterate by

gradual elimination of erratic measurement, e.g. if data

point error is bigger than certain multiple of standard

deviation.

Here the author would like to make a brief excursion.

The classical recommendations say to clean carefully the

3D scan measured data in order to separate just the object

of interest from all other objects and only after this

procedure to proceed to further data processing. However,

this process is very lengthy and sensitive to human

mistakes.

The employed software tools is able to handle roughly

cleaned data and to perform neat cleaning automatically.

The procedure mentioned in previous paragraphs is

capable of doing so especially if it is realized that in the

case of chimneys and similar structures, nearly all

unwanted data points are in reality objects are ladders,

technological equipment, platforms etc. that are located

outside the chimney body itself. Therefore the

modification of the above algorithm to eliminate point if

data point error is bigger than certain multiple of standard

deviation and data point is outside fitted circle. The result

of such optimization is a least square fit circle inscribed in

measured data points.

Other breaking the classical rules is the usage of

incomplete scan. The method described is so robust it

enables usage of partial 3D scan, typically just one-sided

single station scan. The advantages of this approach are

shorter time to prepare scanning as there is no need to

prepare several scans connecting objects, shorter time

perform the scan itself and finally shorter time for data

processing as the process is simplified.

5. Conclusion

The author introduced 3D scan and its usage to measure

the steel structures. More in detail is discussed the problem

of employing 3D scan to evaluate inclination of chimneys

and similar structures and he developed software tool.

Acknowledgements

This work has been part of NOVING OK development

financially supported by OP PIK

CZ.01.4.04/0.0/0.0/16_076/0008881 – project registration

number.

References

[1] KHAN A., TUROWSKI K. A Survey of Current

Challenges in Manufacturing Industry and Preparation

for Industry 4.0. Proceedings of the First International

Scientific Conference “Intelligent Information Technologies for Industry” (IITI’16). Advances in Intelligent Systems and Computing, vol 450. Springer,

Cham, 2016, pp. 15–26, IBSN 978-3-319-33608-4.

[2] DUZI B., JAKUBINSKY J. Brownfield dilemmas in

the transformation of post-communist cities: a case

study of Ostrava, Czech Republic, HUMAN

GEOGRAPHIES – Journal of Studies and Research in

Human Geography, 2013, pp. 53–64, ISSN: 1843–6587.

[3] CSN 73 2604, Steel Structures – Inspections and

maintenance of steel structures of buildings and civil

engineering works, 2012, UNMZ, Praha.

[4] BOSCHE F., Automated recognition of 3D CAD

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model objects in laser scans and calculation of as-built

dimensions for dimensional compliance control in

construction, Advanced Engineering Informatics,

Volume 24, Issue 1, 2010, pp. 10 –118, ISSN 1474-

0346.

[5] NOVOTNY T., FONIOK M., Využití 3D laser scanneru pro mapování existujících konstrukcí, 10.

odborná konference Konstrukce 2019, Nesuchyně, 2019, pp. 61–66, IBSN 978-80-905356-6-4.

[6] CHUAN X., Research on Improved DV-HOP

Localization Algorithm Based on Weighted Least

Square Method, 2008 IEEE International Symposium

on Knowledge Acquisition and Modeling Workshop,

Wuhan, 2008, pp. 773–776, ISBN: 978-1-4244-3530-

2, DOI: 10.1109/KAMW.2008.4810605.

[7] NOVOTNY T., MATSUMOTO E. and SHIBATA T.,

Nondestructive Reconstruction of Layered Acoustic

Medium, Proceedings of the 9-th Computational

Mechanics Conference, Fukuoka, Japan, pp. 271–272,

1996.

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DISTRIBUTED FIBRE OPTIC SENSORS IN CIVIL ENGINEERING APPLICATIONS – SELECTED CASE STUDIES IN POLAND

Tomasz HOWIACKI1

1Faculty of Civil Engineering, Cracow University of Technology,

Warszawska 24, Krakow, Poland

[email protected]

Abstract. Structural health monitoring is a process which allows to obtain information about structural behaviour of the object in its real operation conditions. This information is a base for decision making to improve safety of the structure and is useful to support failure risk management, the benefits of which are expressed in money terms. Thus, it is very important to put attention to the quality and reliability of the information which is directly related to the measuring technique and kind of sensors applied. One of the most promising and breakthrough technologies is distributed fibre optic sensing DFOS, enabling to measure selected physical quantities in geometrically continuous manner over entire measuring length. This brings unprecedented possibilities in the assessment of technical condition. The article presents a brief look for a pilot application within different type of structures during last few years in Poland.

Keywords

Optical sensors, distributed measurements, structural health monitoring, case studies.

1. Introduction

1.1. Structural health monitoring

The information on the behaviour of structures in service conditions is particularly useful to support failure risk management, the benefits of which are expressed in money terms. In the case of the existing, often technically advanced and geometrically complex structures, such additional measurement data will lead to minimising the risk and uncertainties related to the model adopted at the engineering phase of the project. In the case of new technologies, such as state of art materials (composites, lightweight concrete, fibre reinforced soil-cement and

other) this technology is employed to measure pilot structures with the purpose to optimise the design parameters while maintaining the risk at the acceptable level.

1.2. Distributed measurements

In the engineering practice, physical quantities are usually measured by means of spot sensors, so the location of these sensors should be chosen very carefully as it has crucial meaning during data interpretation. Data analysis from spot sensors is particularly difficult for geotechnical and concrete structures because their heterogeneity and the influence of very local phenomena such us discontinuities, cracks or the presence of the larger aggregate grain.

The accuracy and reliability of findings depends on the quality of the gathered data. This results in an on-going lookout for new technologies - economic and enabling a more comprehensive assessment of the structural behaviour. The distributed fibre optic sensors (DFOS) [1] which measure the parameters continuously over the entire measuring length is one of the most promising technologies. Thanks to the phenomena such as Rayleigh scattering, a single optical fibre can replace thousands of traditional point-type strain gauges [2].

Fig. 1: The idea of spot, quasi-continuous and fully-continuous (distributed) measurements.

This approach offers so far unavailable capabilities of analysing the behaviour of structures with taking into account such local effects like e.g. crack in concrete [3].


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That is why during last few years a significant increase in the use of this technique in the world is observed [4]. Practical examples (case studies) within different types of engineering structures in Poland are presents hereafter.

2. Footbridge with hybrid deck

The first example shows smart structure of pedestrian-cyclist footbridge, equipped with linear, optical fibre strain sensors EpsilonRebar produced by SHM System [5]. These sensors, in the form of composite rods being simultaneously the structural reinforcement for the platform slab, were placed along the entire span over the length nearly 80 m – Fig. 2. Thanks to the application of distributed optical fibre sensing technique DFOS it is possible to measure strains, displacements (deflections) and temperature changes in a geometrically continuous manner along the entire length of the footbridge. The sensors integrated with the platform were used to measure selected physical quantities during the hydration of early-age concrete (thermal-shrinkage strains), during activation of dead weight of the slab as well as during the load tests.

Strains distribution measured by selected EpsilonSensor after activation of the dead weight of the deck, which was supported by traverses every 5 m, are presented in Fig. 3 over entire span length of 80 m.

Readings can be performed at any time of the structure operation in order to assess its technical condition (e.g. crack appearing) and to analyse the impact of environmental conditions and other factors, e.g. rheological phenomena.

Fig. 2: The view of the composite reinforcement (including smart EpsilonRebar sensors) before concreting.

Fig. 3: Strain distributions from the deck dead weight measured by EpsilonRebar sensors over entire 80m length, compared with FEM analysis.

3. Steel and composite bridges

Next example relates to steel T. Mazowiecki bridge in Rzeszów, Poland, were distributed optical fibre sensors were installed over entire 150 m long river span [6]. Sensors were glued within the lower and upper part of the steel girder – see Fig. 4.

Fig. 4: Location of distributed fibre optic sensors within the steel girder of T. Mazowiecki bridge in Rzeszów, Poland.

Measurements of strains were performed during normal operation conditions i.e. including uneven loading by temperature changes. Exemplary plot of strains from the lower optical fibre are presented in Fig. 5. They were caused only by temperature and local irregularities results from the presence of the perpendicular ribs and cable anchors.

Fig. 5: Strain distributions in lower part of the girder caused by temperature changes, measured over 150 m span of the bridge.

Knowing the strain distributions in selected heights of girder cross section, as well as boundary conditions within supports, it is possible to calculate vertical displacements with spatial resolution starting from as fine as 5 mm.

Fig. 6: Displacement profile caused by temperature changes, calculated over 150 m span of the bridge.

EpsilonRebars

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Structural health monitoring of bridges based on DFOS technology is becoming more and more popular, especially for the purposes of the load tests. Few other bridges in Poland are equipped with such kind of system, including the first Polish composite beam bridge [7].

4. Concrete columns

The quality of measuring information is especially important for geotechnical applications because there are many uncertainties regarding the theoretical model describing cooperation between the foundations and the substrate as well as including the values of physical parameters. Moreover, the geometry of structural members (e.g. the diameter of the column) can be very different from design assumptions and vary along the depth depending on technology of execution. In presented case study the strain and temperature measurements performed continuously over the entire depth of continuous flight auger (CFA) column are analysed [8]. The measurements were done during the load tests, but also in the early-age concrete, when thermal-shrinkage strains appeared. The EpsilonRebars sensors were used for this purposed, installed in the axis of the CFA columns.

Fig. 7 shows exemplary strain distributions over column depth during its load tests. Local extremes within compression side correspond to the weakest areas with the lowest axial stiffness. Assuming that the elasticity modulus of concrete is constant over the depth, these peaks indicates reduction of the column cross section. It could be also related to the cracks which appeared during concrete hydration and now being closed under compression force. Such kind of information could be crucial for the designers and contractors.

Fig. 7: Strain distributions over the depth of CFA concrete column during its load test.

5. Roads and other line structures

Another group of structures being equipped with DFOS monitoring systems are linear structures like roads, highways, embankments, pipelines, tunnels [9], dams or hydrotechnical structures [10].

In Poland such systems were installed e.g. within concrete sewage collector during its renewal, experimental section of the highway reinforced only with composite rebars, asphalt layers (composite sensors like EpsilonRebar are able to withstand extreme temperature conditions), and within few road embankments.

Fig. 8 shows the spatial visualization of one of the Polish installations within embankment, which was equipped with linear composite sensors by SHM System for strain (EpsilonRebars) and displacements (3DSensor) measurements. Data obtained in geometrically continuous way allowed for the detailed analysis of the structural behaviour of the transmission layer taking into account the cooperation with the substrate strengthened by concrete columns.

Fig. 8: Spatial visualization of road embankment equipped with composite distributed fibre optic sensors: EpsilonSensor for axial strain measurements and 3DSensor for vertical displacement (shape) measurements.

6. Conclusion

The article shows only a brief look for selected installations of distributed fibre optic sensors for structural health monitoring of real structures in Poland. Of course, the presented examples do not cover all DFOS-based systems, which include also:

• CFA piles, CMC piles, SDM piles,

• fibre reinforced soil-cement slurry walls,

• foundation barrettes under three new built tower skyscrapers in Warsaw,

• roads and highways,

• reinforced concrete, prestressed concrete, steel

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and composite bridges and footbridges,

• concrete collectors during their strengthening,

• many other examples.

Practical case studies show the great possibilities of distributed fibre optic technology for structural analysis and assessment of technical condition. They are very durable, reliable, easy to install and what is important, they could be integrated with new structural members during the construction (e.g. embedding into the concrete).

It is also worth noticing that DFOS sensors nowadays are the best and the most versatile for laboratory tests. In Polish technical universities we can find tens of unique examples. Fig. 9 shows the strain distributions within the tension zone of some prestressed concrete slab [11] during its 4-point bending test. Application of EpsilonRebar sensors inside the concrete allowed for detailed analysis of the crack morphology, including their precise location as well as the estimation of their widths.

Fig. 9: Strain distributions within the tension zone of concrete slab, showing the exact crack morphology.

Acknowledgements

Author would like to show gratitude to the SHM System company (Cracow, Poland) which completed the research project called “Development of the new fibre optic sensor allowing for the determination of the vertical and horizontal displacements of the studied objects at the distances of up to 120 km”. This project was funded by the grant won at the National Centre for Research and Development within the framework of Intelligent Development Operational Program 2014-2020 (POIR. 01.01.01-00-0550/15).

References

[1] GLISIĆ, B. and D. INAUDI. Fibre Optic Methods for Structural Health Monitoring. Wiley. 2007.

[2] LI, W. and X. BAO. High spatial resolution distributed fiber optic technique for strain and temperature measurements in concrete structures. International Workshop on Smart Materials &

Structures, SHM and NDT for the Energy Industry. Calgary, Alberta, Canada, October 7-10 2013.

[3] SIEŃKO R., M. ZYCH, Ł. BEDNARSKI and T. HOWIACKI. Strain and crack analysis within concrete members using distributed fibre optic sensors. Structural Health Monitoring, October 8, 2018, DOI: 10.1177/1475921718804466.

[4] Barrias, A., J. R. Casas and S. Villalba. A Review of Distributed Optical Fiber Sensors for Civil Engineering Applications. Sensors. 2016, 16, 748

[5] SIWOWSKI T., R. SIEŃKO, Ł. BEDNARSKI, M. RAJCHEL, T. HOWIACKI and L. WŁASAK. Application of Smart Optical Fibre Reinforcement Bars ‘Epsilonrebar’ for Deformation Measurements of Pedestrian-Cyclist Footbridge in Nowy Sącz, Poland. International Bridge Conference InfraMOST 2019 Bridges in Road and Railway Infrastructure. Wisła, Poland, 16-17 May 2019.

[6] SIEŃKO R., Ł. BEDNARSKI, T. HOWIACKI and KORYCIŃSKI J. Suspension Bridge Deformation Measurements with Distributed Fiber Optic Sensors DFOS. Seminarium Wrocławskie Dni Mostowe WDM2018. Wrocław, Poland 2018.

[7] SIWOWSKI T., R. SIEŃKO, Ł. BEDNARSKI, M. RAJCHEL and T. HOWIACKI. Optical Fiber Strain Measurements of Composite Bridge Members Based on Selected Tests. Seminarium Wrocławskie Dni Mostowe WDM2017. Wrocław, Poland 2017.

[8] SIEŃKO, R., Ł. BEDNARSKI, P. KANTY and T. HOWIACKI. Application of Distributed Optical Fibre Sensor for Strain and Temperature Monitoring within Continuous Flight Auger Columns. 4th World Multidisciplinary Earth Sciences Symposium WMESS. Prague, Czech Republic, 03-07 September 2018.

[9] MONSBERGER, CH. M., W. LIENHART, A. KLUCKNER, L. WAGNER and W. SCHUBERT. Continuous strain measurements in a shotcrete tunnel lining using distributed fibre optic sensing. 9th European Workshop on Structural Health Monitoring. July 10-13, 2018, Manchester, United Kingdom.

[10] SIEŃKO, R., Ł. BEDNARSKI and T. HOWIACKI. Application of optical fiber sensors for structural health monitoring of hydrotechnical structures. In: Budowle Piętrzące - eksploatacja i monitoring. Instytut Meteorologii i Gospodarki Wodnej, Państwowy Instytut Badawczy, Warszawa, Poland 2017, ISBN: 978-83-64979-23-1.

[11] SIEŃKO, R., Ł. BEDNARSKI and T. HOWIACKI. About Distributed Internal and Surface Strain Measurements Within Prestressed Concrete Truck Scale Platforms. 3rd World Multidisciplinary Civil Engineering - Architecture - Urban Plan- ning Symposium WMCAUS. Prague, Czech Republic, 1822 June 2018.

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FREE VIBRATION ANALYSIS OF FUNCTIONALLY GRADED

MATERIAL PLATES USING MK MESHFREE METHOD WITH A

SIMPLE KIRCHHOFF PLATE THEORY

Vuong Nguyen Van Do1

1Applied Computational Civil and Structural Engineering Research Group, Faculty of Civil Engineering, Ton Duc

Thang University, Ho Chi Minh City, Vietnam

[email protected]

Abstract. In this paper, a simple modified Kirchhoff theory is captured for analysis of free vibration analyses of functionally graded material (FGM) plate based on modified Moving Kriging method (MK). The locking phenomenon of thin plates is ignored due to taking account the shear deformation effects into modified theory. Regarding to the proposed refined plate theory, the independent unknowns reduce one variable and exist with four degrees of freedom per node. The simulated free vibration results employed by the MK interpolation are compared with the other analytical reported in the literature reviews to verify the effectiveness and the accuracy of the modified mesh-free method. Results demonstrated that the modified mesh-free of Moving Kriging interpolation can effectively predict the numerical calculation as compared to the exact solutions. The obtained numerical results indicate that the present method is stable and well accurate prediction to estimate with other published analyses.

Keywords

Functionally graded material (FGM) plate, Mesh-free, Moving Kriging interpolation (MK), locking free.

1. Introduction

Conventional laminated composite plate of the functionally graded materials (FGM) proposed by Bever and Duwez [1] have been applied in a variety of engineering industries because of their distinctive material properties, which vary continuously through the thickness. Their characteristics can be tailored in many applications and various working environments. In the plates and shell

structures, the smoothness and continuously changing in microstructure from the top to the bottom layer can make the materials displayed in distinct phases regarding to ceramic and metal. Therefore, the analyses of displacement, stress, dynamic problems of natural frequencies and buckling responses are really crucial for FG material responses.

Besides the number merits of material properties of FGM plates, then many plate theories have been researched. The typical method such as the classical plate theory (CPT) [2] with Kirchhoff-Love assumptions for thin plate gave acceptable results. Nevertheless, the effects of shear deformations were not incorporated into the model, then it leads to totally unsuitable numerical calculations in thick plates. The large number of significant theories had been written in FEM [3] including the shear deformation to overcome the shortcomings of classical plate theory. However, these methods are over-stiffness when the plates become too thin. It is also known that the HSDTs with FEM are complicated and increased the higher variables in numerical analysis due to the use of linear shape function.

Due to the disadvantages of FE analysis, the mesh-free method developed by Ted. Belytschko [5] could be available to attain the better accuracy results. In the present study, the cubic form taken account into the Moving Kriging shape function is the target to ignore the dependence of coordinate meshes as well as disappearance of any coefficients in the chosen form. The high accuracy in analysing FGM plates of the dynamic vibrations is employed by a simple Kirchhoff theory. The verified numerical examples have shown a good validation between the proposed method and the other various published reported literatures. Results illustrated that the mesh-free Moving Kriging can effectively predict the dynamic vibration of the FGM isotropic plates.


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2. FGM plate on The Kirchhoff theory for

2.1. The Kirchhoff theory

Considering the Kirchhoff plate theory with the domain given for the mid-plane of the plate, the displacement variables of u0, v0, and bending displacement b

w belong to three x; y; z directions. To improve this model for analysis both moderately thick and thin plates, a modified transverse displacement can be separated into bending and shear parts. A modified formulation of Kirchhoff theory is described by

( ) ( )

( ) ( )

( ) ( ) ( )

0

0

, , ,

, , ,

, , , ,

b

b

b s

wu x y z u x y z

x

wv x y z v x y z

y

w x y z w x y w x y

= −

= −

= +

,2 2

h hz

−

(1)

The displacement field is given in Eq. (1) included four unknown variables of 0 0, , ,b s

u v w w . The number of independent unknowns of the present theory are reduced one variable as comparison with the Reissner-Mindlin FSDT theory.

The relationship of strains and displacement equations is described by

0 1[ ]T

p xx yy xy z = + =

T

xz yz s = γ ε=

The dynamic equation of simple Kirchhoff theory based on Ref.[6] can be obtained by

1 20 0 0 0

2 31 1 1 1

d d d 0

T T

T s

s s

I I

I I

+ + =

u uA BD

u uB D

where

( ) ( )/2

2

1 2 3

/2

, , ( ) 1, , d

h

h

z z z z−

= I I I , 0 [ ]T

b su v w w= +u ,

1 [ ]Tb bw w

x y

=

u

and

/2 /22

ij ij ij/2 /2

A ,B ,D (1, , )Q d ; D G dh h

s

ij ij s ijh h

z z z k z− −

= =

2.2. Formulation for isotropic FGM plates

The isotropic homogeneous plate is separated into two different material phases in which ceramic and metal are distributed at the top and bottom layers, respectively. In this paper, the homogenized formulation of the rule of mixture is used to homogenize the material parameters.

The volume fraction of ceramic phase is described as [4].

( ) 0.5

n

c

zV z

h

= +

, ,2 2

h hz

− and 1m cV V= − (2)

where m and c are expressed to the metal and ceramic. The scale parameter n is representative to the gradation of material properties varying through the thickness

3. A Moving Kriging (MK) interpolation function

The MK interpolation is used to build the shape functions and its derivatives through a set of nodal points. The estimation of the arbitrary distribution point (x )iu can be defined in the subdomain

x andx . The

interpolation domain is based on all nodal values, whereix ( [1, ])i n , n is a set of nodes in the support domain

x.The MK distribution interpolation can be applied to

( )hu x for every x in the support domain

x and is expressed as

( ) [ ( ) ( ) ]h T Tu x p x A r x B u= +

(3) The matrices A and B can be derived by the following equations

1 1 1( )T TA P R P P R

− − −= ; 1( )B R I PA−= − (4)

In the Eq. (4), P is the matrix of size n m , which contains the values of all polynomial basis functions at n nodes inx ,

1 1 2 1 1

1 2 2 2 2

1 2

( ) ( ) ... ( )

( ) ( ) ( )

( ) ( ) ( )

m

m

n n m n

=

p x p x p x

Pp x p x p x

p x p x p x

and ( )r x vector is defined by

1 2( ) { ( , ) ( , ) ( , )}T

nR R Rr x x x x x x x= (5) where ( , )i jR x x is the covariance basis function regarding

an arbitrary pair of n nodes ( , )i jx x . In this paper, we propose a polynomial function which uses the cubic polynomial function, normalized as

2 3

2 32 13 2

2 3

2 34 13 2

4 4 0

( ) 4 4 4 1

0

ij

ij ij

s s s

ij

i ij ij ij

s s s s

rr r for

r r r

rR r r r r for

r r r r

otherwise

− +

= − + −

(6) where sr is the scale factor used to normalize the distance.

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Here sr is taken to be the maximum distance between a pair

of nodes in the support domainx.

The covariance matrix n nR R is expressed following as

1 2 1

2 1 2

1 2

1 ( , ) ... ( , )

( , ) 1 ... ( , )[ ( , )]

( , ) ( , ) 1

n

n

i j

n n

R R

R RR

R R

=

x x x x

x x x xR x x

x x x x

(7)

4. Numerical results and discussion

This section presents several non-dimensional fundamental frequencies = /m mh E of (SSSS) simply supported plates to verify the effectiveness of the present simple Kirchhoff theory using MK meshfree method. The material for the first set is of Aluminum-Ziconia (Al/ZrO2), while the second one is of aluminum and alumina (Al/Al2O3) can be tabulated in Table 1. The effective characteristics of functional graded materials are assumed to homogenize by the rule of mixture. In the computational calculations, FGM plate was discretized by 23×23 regular nodes with 23×23 quadrilateral background mesh for the integration and the scaling factor ( ) of 2.4 was used to capture the size of the influence domain. The free vibration analyses for the isotropic Al/AL2O3 FG thin plate of length to thickness ratio, a/h= 100 tabulated in Table 2 have proved the comparison between the proposed theory and the conventional Kirchhoff plate theory. Furthermore, considering the numerical results for the moderately thick FG Al/ZrO2 plate of a/h=5 displayed in Table 3, the computed frequencies from suggested theory are well matched to the exact 3D solutions [7] and slightly higher than others reported by SSDT[9] and Quasi-3D [8]. It is noted that the accuracy of the numerical results for the thin to moderately thick plates is dependent on the modified Kirchhoff theory irrespective of different FG material constituents, meanwhile, almost results from CPT theory are always over-estimated due to the shear part not be taken account into the calculation.

Tab. 1: Material properties.

Al ZrO2 Al2O3

E (GPa) 70 200 380

0.3 0.3 0.3

(kg/m3) 2707 5700 3800

Table 2. The natural frequency = /m mh E of

SSSS Al/Al2O3 square plate with a/h=100.

Model a/b=1 a/b=2

n

0 0.5 1 2 0 0.5 1 2

Analytical [7]

115.86

98.01

88.30

80.35

72.39

61.33

55.12

50.07

Present 115.83

98.09

88.39

80.37

72.46

61.36

55.29

50.27

CPT 116.03

98.25

88.54

80.50

72.50

61.39

55.32

50.29

Table 3. The natural frequency = /m mh E of

SSSS Al/ZrO2 square plate with a/h=5.

Model z n

0 0.5 1 2 3 5 10

Exact [7] - - 0.21

92

0.2197

0.2211

0.2225

-

Quasi-3D [8]

0

- - 0.2152

0.2153

0.2172

0.2194

-

SSDT [9] 0 - - 0.21

84

0.2189

0.2202

0.2215

-

SSDT [9]

0

- - 0.2193

0.2198

0.2212

0.2225

-

Present 0 0.2462

0.2223

0.2190

0.2202

0.2220

0.2234

0.2223

CPT 0 0.2462

0.2542

0.2483

0.2477

0.2500

0.2529

0.2523

5. Conclusion

In this paper, A Moving Kriging in Meshfree method for FGM isotropic plates has been proposed for a simple improved Kirchhoff plate theory. Based on those obtained in this study, the following conclusions can be given:

The Moving Kriging interpolation method is chosen in the present method could give the stable solutions in the numerical analysis and better than the conventional Kirchhoff theory.

The simple Kirchhoff theory of which the transverse deflection w separates into bending ( b

w ) and shear ( sw ) components effectively predicts the FG plate from

the moderately thick to thin plates. It is worth concluding that the simple present theory is highly reliable to assess the results for many types of FGM plates.

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Acknowledgements

This research is funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 107.02-2018.28.

References

[1] Bever M B, Duwez P E 1972 Gradients in composite materials. Mater Sci Eng 10 1–8.

[2] Dawe D J, LAM S S E, Azizian Z G 1992 Nonlinear finite strip analysis of rectangular laminates under end shortening, using classical plate theory. Int. J. Num. Meth. Eng 35 1087-1110.

[3] Talha M, Singh B N 2010 Static response and free vibration analysis of FGM plates using higher order shear deformation theory. Applied Mathematical Modelling 2010; 34 (12): 3991–4011.

[4] Reddy J N 1984 A simple higher-order theory for laminated composite plates. J. Appl. Mech 51 745–752.

[5] Belytschko T, Black T 1999 Elastic crack growth in finite elements with minimal re-meshing. International Journal for Numerical Methods in Engineering 45 601–620.

[6] Matsunaga H 2008 Free vibration and stability of functionally graded plates according to a 2D higher-order deformation theory. Compos Struct 82 499–512.

[7] Vel S S, Batra R C 2002 Exact solution for thermoelastic deformations of functionally graded thick rectangular plates. AIAA Journal 40 1021–1033.

[8] Qian L F, Batra R C and Chen L M 2004 Static and dynamic deformations of thick functionally graded elastic plate by using higher-order shear and normal deformable plate theory and meshless local Petrov-Galerkin method. Compos Part B: Eng 35 685–697.

[9] Neves A M A, Ferreira A J M, Carrera E, Roque C M C, Cinefra M and Jorge R M N 2012 A quasi-3D sinusoidal shear deformation theory for the static and free vibration analysis of functionally graded plates. Compos Part B: Eng 43 711–725.

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FINITE ELEMENT APPROACH ON DYNAMIC RESPONSE OF EULER-BERNOULLI BEAM SUBJECTED TO MOVING VEHICLES

Vuong Nguyen Van Do1, Le Dang Minh Tu1

1Applied Computational Civil and Structural Engineering Research Group, Faculty of Civil Engineering, Ton Duc

Thang University, Ho Chi Minh City, Vietnam

[email protected]

Abstract. Dynamic analysis of beam structures subjected to moving vehicles using a finite element Euler-Bernoulli formulation is presented in this paper. The method utilizes finite element method using the basic cubic functions for analysis implementation. The Dalambert‘s principle is used to set up the moving differential equations system contacting between vehicle and beam and the Newmark’s modified average acceleration method is utilized to solve the differential equations. The validations of the proposed method included a complicated moving vehicle and rough pavement effects are compared to the precisely analytical results. Compared with most existing methods of finite element method (FEM) and readily analytical solutions, the present technique indicated the effectiveness of present FEM method and its well accurate prediction for suitable simulating the interaction model of the bridge structures and complicated vehicles. Through these results, the thesis gives recommendations and proper measures to minimize the impact of vehicle on complicated long structures such as stayed cable bridge or suspension bridge.

Keywords

Euler-Bernoulli beam, dynamic behavior, moving vehicles, cubic function, Finite element.

1. Introduction

The behavior of beam structures under a moving vehicle system has been proposed and implemented continuously over a century. The first analytical problem of a single beam where its mass was negligible by imposing a constant speed moving force was introduced by Timoshenko [1]. The relating problems were considered the effects of elastic foundations, moving mass and deflection dependent moving load [2, 3]. Several types of railway bridges traversed by steam locomotives were

presented by Inglis [4] using harmonic analysis. The exact solution of the dynamic response of bridges under moving loads was reviewed in detail by Timoshenko [1]. An analytical solution with a succession of massless point loads for an Euler-Bernoulli beam had been produced by Savin [5]. Yeong et al. [6] had investigated the dynamic vibration of simple beams due to the high speed trains and also identified the various factors for making an optimal design. Subsequent were the parametric studies which consisted of moving mass and mass of the girder for the dynamic responses based on investigations of Mechaltsos [7-9]. Wang and Chou [10] employ the large deflection theory to derive the equations of motion of the Timoshenko beam due to the coupling effect of an external force with the weight of the beam. Through all above researches, it is realized that the dynamic responses of moving vehicle on beam generated from finite element analysis have some exposed difficulties. It is found in the simulation which interacts between moving mass and beam, the mass acceleration and velocity of vehicle at the contact point require the derivatives of the shape function could make the unsymmetrical stiffness matrix and difficulties in numerical analysis. In this work, a theory with a frame work of the finite method is developed for a single-foot dynamic system moving on an elastic beam. The resonant vibration is also explained when the multiple discrete moving concentrated loads traversed over the supported beam. Finally, the FEM method is applied to a realistic smooth surface for a complicated vehicle system to evidence the utility of the present FEM method. In view of the above results, FEM is clearly to suggest itself as efficient implementation and a viable of the main FEM basic concepts to an improved accuracy and thus a promising approach. A discussion in numerical examples is shown to validate high performance of the proposed method.


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2. A beam formulation based on FEM cubic function

2.1. The Euler–Bernoulli beam formulation

The displacement field u of the Euler-Bernoulli beam is approximated as

1

( ) ( )n

h

i i

i

u R q =

= (1)

where n is the number of basis functions,iR is rational

basis function, iP is node and

i iq w= is the nodal degree

of freedom regarding to the control point i . 2

2

T

p

w

x

=

(2)

By substituting Eq.

(2) into Eq.(1), the in-plane strains can be rewritten as

,

1 1

( )n n

T T T

p i xx i i i

i i

R q B q= =

= =

(3)

The dynamic equation considered the free vibration analysis can be obtained by a weak form as

T

p pEI d d

= u Au (4)

2.2. Elastic beam subjected to a moving concentrated force.

For the dynamic response of an elastic beam subjected to a moving concentrated force, the governing decretization equation of motion is normally given as:

M d C d K d f+ + = (5)

where M is the structural mass matrix, C is the

structural damping matrix, K is the structural stiffness

matrix, f is the interaction force vector and d , d ,

d are denoted as the acceleration, velocity and displacement vectors, respectively.

2.3. Elastic beam subjected to a moving one-axle dynamic system

The moving system is assumed to be without losing contact on the beam surface. The beam has a constant cross-section A , a length Land a second moment of inertia I . The material characteristics of the beam are Young’s modulus E , and the mass density .

The governing equation systems for the interaction model

between beam and single axle vehicle using FEM analysis formulations can be obtained as following

1 1 1 1 2 1 1 2(w ) (w ) 0m w c w k w+ − + − = (6)

and

2 2 1 1 2 1 1 2 2 2 3(w ) (w ) (w ) 0m w c w k w k w− − − − + − = (7)

where 1w ,

2w ,3w are the vertical motions of the masses

measured from the static position,1k ,

2k are the springs connecting two masses and

1c is a damping coefficient of viscous dampers of vehicle.

The deformation between the contact point 3w and the

elastic beam may be neglected, therefore the displacement ( , )w x t of beam at the contact point is equal together.

3. Discussion

3.1. Analysis of one moving foot for elastic beam

The first example is employed here to study a dynamic behaviors of an elastic beam imposed by a concentrated moving load in which the influence of the inertia of the vehicle mass is negligible. The beam characteristics are of length 34L m= , stiffness 10 29.92 10EI Nm= and weight for unit length 11400m kg m= . The force is set

by 347000N and the critical velocity crv L EI m= .

The consistent mass and stiffness matrices are derived from the cubic interpolation function. The support beam structure is discretized into m nodes regarding to the number of control points connected by m p− beam elements.

The verification for a concentrated moving load is evidenced by FEM to evaluate the dynamic response of thin beam under various constant velocities. Such obtained solutions from above methods are compared to the other FEM derived by Lin and Trethewey [11] and exact results examined by Warburton [12]. The different values of

fT are evaluated at the central deflection of elastic

beam. The symbol fT designates the fundamental period of beam and denotes the whole of travel time for the moving load from left end to right end position. In Fig. 1, when the speed of moving force is sufficiently low, i.e. the dynamic behavior at the central position is small and approximated to the static displacement. This is apparent as the curve regarding to the speed parameter at

0.1fT = . When the speed becomes further decreased, the dynamic behavior closely approaches to the static deflection. Tab. 1 also displays the results of dynamic deflection factor which is defined as the ratio of the maximum dynamic displacement dividing to the

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maximum static displacement at the central elastic beam. A very good agreement is compared between the analytical results [12] and those achieved from developed FE model. This work illustrates that the computational implementation has been successful in simulations of present finite element methods. Tab. 1: Comparison of impact factors for different theories.

fT Impact factor

Exact [12] FEM [11] FEM 0.1 1.050 1.053 1.05216

0.5 1.250 1.252 1.25857

1.0 1.707 1.705 1.70503

1.234 1.743 1.730 1.73250

1.5 1.710 1.704 1.70143

2.0 1.550 1.550 1.54792

Fig. 1: Central dynamic displacement of a simply supported beam subjected to a concentrated load moving with various constant speeds.

For the next computation, the dynamic interaction between a one-foot dynamic system and Euler-Bernoulli beam is considered. The moving system is of spring mass

1m in which its stiffness k and damping c are presented. The spring of tie 2k and mass 2m are not included in the vehicle model. All of these matrices are dependent on time, and changed within the system matrix when the moving sprung mass travels from starting point to end point of the beam. Tab. 2 presents the obtained numerical results of FEM to the FE solutions derived by Lin and Trethewey [11]. The dynamic impact comparisons of fixed-fixed beam are very good agreement between FEM and those published in Refs. [11]. Considerable savings are concluded that the proposed method is completely reasonable to reduce the computational time and stable solutions in requiring for implementation.

Tab. 2: The impact factors of middle displacement for fixed-fixed beam subjected to one-foot moving mass.

fT Lin et al. [11] FEM Error (%) 0.1 1.028 1.0303 0.22

0.5 1.206 1.2182 1.01

1.0 1.533 1.5372 0.27

1.5 1.460 1.4589 -0.08

2.0 1.307 1.3062 -0.06

4. Conclusion

The dynamic behaviors of an Euler-Bernoulli beam under moving vehicle are developed by present finite element method can be drawn as following:

The comparison results of analytical formulation, finite element method and published approach proved that the present FEM method is suggested itself as the effective tool in computational dynamic behaviors of solid structures as Euler-Bernoulli beam.

The Euler-Bernoulli beam has existed drawbacks in analyzing the high-frequency vibration, therefore dealing with Timoshenko beam is a solution to solve the existing shortcomings of Euler-Bernoulli beam. Moreover, this study also developed the beam element in two dimension, however vehicles or trains are responded into three-dimensional schemes, then the extensively exploiting for these models in the three dimensional beam is crucial to assess the dynamic responses of the beams under the complicated moving loads as a next study.

Acknowledgements

This research is funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED) under grant number 107.02-2018.28.

References

[1] S.P. Timoshenko, On the forced vibration of bridges, Philosophical Magazine 43 (257) (1922) 1018-1019.

[2] J.T. Kenny, Steady state vibrations of beam on elastic foundation for moving load, Journal of Applied Mechanics 21 (1954) 359-364.

[3] Rao N.S.V Kameswara, One set of separation between a beam and a tensionless foundation due to moving loads, Journal of Applied Mechanics 41 (1974) 303-305.

[4] C.E. Inglis, A mathematical treatise on vibration in railway bridges. Cambridge: Cambridge University Press 1934.

[5] E. Savin, Dynamic amplification factor and response

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spectrum for the evaluation of vibration of beams under successive moving loads. Journal of Sound and Vibration 248 (2) (2001) 267-288.

[6] Y.B. Yang, J.D Yau, L.C. Hsu, Vibration of simple beams due to trains moving at high speeds, Engineering Structures 19 (1997) 936-944.

[7] G.T. Michaltsos, Dynamic behavior of a single-span beam subjected to loads moving with variable speeds, Journal of Sound and Vibration 258 (2) (2002) 359–372.

[8] G. Michaltsos, D. Sophianopoulos, A.N. Kounadis, The effect of a moving mass and other parameters on the dynamic response of a simply supported beam, Journal of Sound and Vibration 191 (3) (1996) 357-362.

[9] G.T. Michaltsos, A.N. Kounadis, The Effects of Centripetal and Coriolis Forces on the Dynamic Response of Light Bridges Under Moving Loads, Journal of vibration and control 7(2001) 315-326.

[10] R.T. Wang, T.H. Chou, Non-linear vibration of Timoshenko beam due to a moving force and the weight of the beam, Journal of Sound and Vibration 218(1) (1998) 117-131.

[11] Y.H. Lin, M.W. Trethewey, Finite element analysis of elastic beams subjected to moving dynamic loads, Journal of Sound and Vibration 136(1990) 323–342.

[12] G.B. Warburton, The dynamic behavior of structures. Oxford: Pergamon Press (1976).

http://www.sciencedirect.com/science/article/pii/S0022460X96901273



http://jvc.sagepub.com/search?author1=G.T.+Michaltsos&sortspec=date&submit=Submit

http://jvc.sagepub.com/search?author1=A.N.+Kounadis&sortspec=date&submit=Submit

http://www.sciencedirect.com/science/journal/0022460X

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NONLINEAR MODEL OF SOIL-SLAB INTERACTION

Zdenka NEUWIRTHOVA1, Radim CAJKA1

1 Department of Structures, Faculty of Civil Engineering, VSB - Technical University of Ostrava, 17. listopadu, Ostrava, Czech Republic


Abstract. Concerning numerical modelling of nonlinear materials, it is important to use appropriate material model in order to obtain reliable results. This article focuses on soil-slab interaction. The numerical model of soil and slab is made in Ansys. Both parts are connected by contact. The soil model is assumed as half-space; therefore, half-sphere model was selected. For the soil model Mohr-Coulomb theory was used. The nonlinear concrete model uses Drucker–Prager yield criterion. Deformation in the middle of the slab was computed in this article. The deformation was consequently compared to the approximated value got from experimental testing.

Keywords

Ansys, Concrete, Contact task, Finite Element Method.

1. Introduction

There are different approaches in the soil-structure interaction and the scientists are still trying to figure out new, more effective, simpler or faster and more accurate way of modelling.

The scientists of India made large summarization of the problematics [1], defining all different approaches and their area of application. From the comparison of analytic approaches, the finite element method seems to be the most actual with the largest area of application these days.

Depending on the size of the numerical model, the whole upper structure with the subsoil can be modelled or the model can be divided into upper structure and the subsoil with the foundations [2].

Some material models are very precious [3] but their use is limited by the demands on computers and computing time. Therefore, finding way how to include them into standard calculations needs to be considered.

2. Numerical model

The numerical model was done in Ansys Workbench 18.0. The model consists of two parts, the subsoil and the concrete slab. Both parts are connected by frictional contact with the friction coefficient of 0.05. All input parameters are based on the slab D14_G05 that was tested in 2017 using special testing equipment named Stand in the Faculty of Civil Engineering in Ostrava (Czech Republic). Solid 65 was used for both model parts.

Values from laboratory test as input to numerical model

Variable Amount

Uniaxial tensile strength 2.72 MPa

Uniaxial compressive strength 30.91 MPa

Elastic modulus 19.67 GPa

Poisson´s ratio 0.3

Biaxial Compressive strength 37.09 MPa

Tab. 1: Soil model input parameters

Variable Amount

Elastic modulus 12.5 MPa

Poisson´s ratio 0.35

Initial Inner Friction Angle 19.3 °

Initial Cohesion 9.0 MPa

Dilatancy Angle 0 °

Residual Inner Friction Angle 10 °

Residual Cohesion 6.96 MPa

Initial Tensile Strength 3.0 MPa

Residual Tensile Strength 2.4 MPa

The concrete slab has dimension 2 x 2 x 0.15 m and is located in the middle of the subsoil. The slab is loaded in the centre through the area 0.4 x 0.4 m by the pressure of

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350 kN. The nonlinear material model was selected using Drucker–Prager yield criterion. In the Table 1 laboratory data as well as numerical model input characteristics can be found.

The subsoil model is based on half-space theory and has a shape of half-sphere supported as pinned through the whole curved area (Fig.1). The diameter of the subsoil was set to tenfold the slab space, therefore radius of the sphere is 10 m. The nonlinear material model was selected as Mohr-Coulomb. In the Table 2 there are input characteristics.


The model was solved using Newton Rapson method. The model has 39913 nodes and the solution took 3 min and 41s. The maximum resulted deformation in the middle of the slab is 26.86 mm (Fig. 1).

The real deformation cannot be measured in the middle of the slab because the loading piston was here. Therefore, the maximum deformation in the middle of the slab was approximated from other potentiometers. Approximated deformation is 31.78 mm. This value can be compared to the result of numerical solution.

Fig. 1: Final deformation on the concrete slab in the centre cross-section of the model.

We can see that the numerical solution results in smaller deformation than approximated value. This may be caused by several factors. First one is approximation method. There were only four potentiometers in the middle cross-section of the slab. Therefore, 3rd order polynomial curve has been used for interpolation. The deformation curve of the beam on the elastic subsoil is described by 4th order differential equation, therefore the polynomial curve at least fourth order should be used for interpolation.

Another factor to consider is the size of the modelled area. The diameter was set to tenth time slab dimension. But it is only assumption. We expect different deformation results upon changing that input parameter based on this study [4].

4. Conclusion

The approximated experimental value differs from numerical solution result by 15%. This is caused by the inaccurate approximation and by the size selection of the modelled area.

Acknowledgements

This paper was supported by the Student Grant Competition held at Faculty of Civil Engineering, Technical University of Ostrava within the project No. SP2020/82 “Nonlinear model of concrete slab-soil interaction using the supercomputer” and by the Moravian-Silesian Region under the program “Support of Science and Research in the Moravia-Silesia Region 2017” (RRC/10/2017).

References

[1] Wahkhade, R. a Yuwaraj G. Study on Soil-Structure Interaction: A Review. International Journal of Engineering Research. 2016, 5. 737-741. 10.17950/ijer/v5i3/047

[2] Králik, J. a Králik, J. jr. Analysis of Soil-Structure Interaction Effects of NPP Structures on Nonhomogeneous Subsoil. Sborník vědeckých prací Vysoké školy báňské - Technické univerzity Ostrava. Řada stavební, 2019, 19(1), 15-21. DOI: 10.35181/tces-2019-0003. ISSN 1213-1962.

[3] Shahbazi, S. a Rasoolan, I. Meso-scale finite element modeling of non-homogeneous three-phase concrete, Case Studies in Construction Materials, Volume 6, 2017, Pages 29-42, ISSN 2214-5095, https://doi.org/10.1016/j.cscm.2016.10.002

[4] NEUWIRTHOVÁ, Z. a ČAJKA, R. Parametric study of input parameters of soil-structure interaction based on elastic halfspace theory. WSEAS Transactions on Applied and Theoretical Mechanics, 2018, 13(21), 167-174. ISSN 1991-8747. E-ISSN: 2224-3429.

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AIR QUALITY AND MORPHOLOGICAL CHARACTERISTICS FOR

HEALTHY LIVING COMMUNITY IN SHENZHEN

Beisi JIA1, Sibei LIU1, Michelle NG1

1Department of Architecture, Faculty of Architecture, the University of Hong Kong,

Pokfulam Road, Hong Kong, P.R China


Abstract. This paper investigates the relationship of

urban morphology and air quality of living estates for 3

cases selected from high dense Pingshan district in

Shenzhen. It utilized a monitoring equipment, a long-term

satellite-based vegetation index, and computer modelling

to estimate the spatial-temporal variability of negative

(Oxygen) Ion, PM2.5, SO2 and NO2. The study reveals

the influences of urban design, land use and landscape

pattern on concentration of negative (Oxygen) Ion, and

pollutants in spatial variation, including the

identification of influential landscape classes.

Keywords

Air quality, urban morphology, negative (Oxygen) Ion

concentration, landscape

1. Introduction

In 2015, the UN re-emphasized the interconnected nature

of global development efforts by setting 17 Sustainable

Development Goals (SDGs). Health promotion efforts,

grounded in a health cities approach, can contribute to

achieving these goals, including SDG 11: “make cities and human settlements inclusive, safe, resilient and

sustainable”.

Shenzhen, a fast growing city in the south of China is

promoting livable and sustainable community. A

sustainable community attempts to increase public transit

ridership, mixed-use, high density, pedestrian-friendly

development can be integrated around public transits. It is

characterized by high living density, safe, mixed-use,

pedestrian-friendly developments. These new urban

types promote higher residential densities, with plot ratio

of 5-6 in Shenzhen) than typical suburbs. In mixed land

uses, it suggests a mix of residential, commercial, and

civic uses. It promotes a street pattern that allows drivers

and pedestrians a variety of path options with distinct

high rise architectural characters with public open spaces.

However, high density of mix-use raises concerns about

air quality. The concept of green urbanism takes nature as

integral to the city itself and brings nature and better air

quality into the life of city dwellers. It contributes to

amelioration of the physical urban environment by

reducing pollution, moderating the extremes of the urban

climate, and contributing to cost-effective sustainable

urban drainage systems. It also improves the urban image

and quality of life; and (5) increasing the economic

attractiveness of a city and fostering community pride.

Greening also has health benefits and an educational

function as a symbol or representation of nature. Finally,

greening aims also to preserve and enhance the ecological

diversity of the environment of urban places.

This research based on literature review, computer

modelling, morphological analysis and site survey

equipped with air quality monitoring investigated the

urban design of living communities in relation to the air

quality from November 2019 to January 2020.

2. Research Methods

A total of three types of evaluation methods are

conducted: computational simulation of urban typology,

on-site measurement and literature analysis.

Computational environment simulation includes Ecotect

and numerical simulation software such as ENVI-met for

calculation of site environmental patterns. The field

measurement requires selection of measurement points at

the site and the environmental parameters measurement

through instruments in three weeks from November 2019

to January 2020.

Three living estates were selected based on Urban land

use, i.e. land surface classification scheme – local climate



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zone (LCZ), both built-up areas and natural land and

Landscape pattern, three class-level landscape metrics

were selected to represents the spatial pattern of each type

of land use/landscape classes (percentage of landscape

types (PLAND), Largest Patch Index (LPI), Aggregation

Index (AI), Connectance Index (CONNECT)) .

The studied negative (Oxygen) Ion and pollutants were

measured at 26 monitoring stations of different

microenvironments using a mobile monitoring device in

the study area.

Two widely used landscape-level metric: contagion index

(CONTAG) and Shannon’s Evenness Index (SEI) was adopted to quantify the diversity of the land use. Each

street is analyzed as a set of slices to propose a couple of

morphology indices for quantitatively assessing the actual

street morphology.

Pollutant transport rate of mean flows and turbulent diffusion, net escape velocity and age of air are obtained

from computational fluid dynamics (CFD) simulations.

The symmetry ratios were studied: the street smoothness

ratio (RSmoothness); the opening ratio (R1+2); the no-

opening ratio (R0); street continuity ratio (RContinuity);

the street spatial closure ratio (RClosure);

Air quality was first examined against four kinds of environmental backgrounds, such as density of road line,

urban built areas, landscape coverage, and the proximity

(spatial distance) to the country park, Maluan Mountain

near the site (Fig.1). Urban land cover was correlated

with AQI to evaluate the urban land cover contribution on

air pollution, particularly then the relationship between

Air quality index (AQI) and visibility was analyzed.

Fig. 1: The site of case studies

3. Research findings and conclusion

The high levels negative (Oxygen) Ion, e.g. 1200- 2500

μg/cm3, accumulate in the approximate area of country

park, and decreasing dramatically towards the inner areas

of living district, to a level about 500 μg/cm3. The level

of shading and size of public landscape in the urban areas

has miner impact to the level of negative (Oxygen) Ion.

The morphological patterns of high density and mix-use

estates play an important role in the air quality. Air

quality has distinct spatial heterogeneity. In terms of the

street patterns, the oblique intersections can also greatly

improve the street ventilations. It is because the wind

speed is the main determinant of air quality in the city —when wind speed is greater than 4 m/sec, air quality can

be significantly improved.

Urban impervious surface makes a contribution to the

severity of air pollution — that is, with an increase in the

fraction of impervious surface in a given area, the air

pollution is more severe. The results show that the street

morphology characteristics, including the street width,

lateral openings and intersections, are closely related to

the air flows in street canyons.

The air quality improves with an increasing aspect ratio

of open spaces owing to a larger vertical exchange,

suggesting larger open spaces are of better air quality.

The lateral openings and intersections of open spaces

have important effects on the air flows in space canyons.

The octagon intersections are favorable for air flowing

through the lateral openings and improve the channel

flows.

Acknowledgements

The research was financed by Zhaobangji Properties

Holdings Limited and Graduate School of the University

of Hong Kong in a project “Evaluation on Housing of

Zhaobangji Property in Pingshan, Shenzhen” in 2019-

2020.

References

[1] HAN, L., ZHOU, W., LI, W., MESHESHA, D. T.,

LI, L., & ZHENG, M. Meteorological and urban

landscape factors on severe air pollution in Beijing.

Journal of the Air & Waste Management

Association. 2015, 65(7), 782-787.

[2] SHEN, J., GAO, Z., DING, W., & YU, Y. . An

investigation on the effect of street morphology to

ambient air quality using six real-world cases.

Atmospheric Environment. 2017, 164, 85-101.

[3] WU, C. D., CHEN, Y. C., PAN, W. C., ZENG, Y. T.,

CHEN, M. J., GUO, Y. L., & LUNG, S. C. C. Land-

use regression with long-term satellite-based

greenness index and culture-specific sources to

model PM2. 5 spatial-temporal variability.

Environmental pollution. 2017, 224, 148-157.

[4] SHI, Y., REN, C., LAU, K. K. L., & NG, E. .

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Investigating the influence of urban land use and

landscape pattern on PM2. 5 spatial variation using

mobile monitoring and WUDAPT. Landscape and

Urban Planning. 2019, 189, 15-26.

[5] Y., DOVLATABADI, A., EBRAHIMNEJAD, A., &

LÖWNER, M. O. (2019). Estimate annual and seasonal PM1, PM2. 5 and PM10 concentrations

using land use regression model. Ecotoxicology and

environmental safety. 2019, 174, 137-145.

[6] United Nation: The 2030 Agenda for Sustainable

Development

https://sustainabledevelopment.un.org/content/docu

ments/21252030%20Agenda%20for%20Sustainable

%20Development%20web.pdf

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“URBAN – SPRAWL” AS AN ASPECT DAMAGING SUSTAINABLE URBAN DEVELOPMENT - THE BACKGROUND OF THE

PHENOMENON ON THE EXAMPLE OF THE CZECH REPUBLIC

Dagmar KUTA1, Marek TEICHMANN1, Stanislav ENDEL1, Lucie HURDALKOVA2

1Department of Urban Engineering, Faculty of Civil Engineering, VSB - Technical University, Ostrava 2Department of investment and city development, Municipality, Nachod


Abstract. Urban development is a challenge for cities in terms of various complex social, environmental and economic impacts. "Urban - sprawl" has become commonplace due to the rate of population growth at the global level. The growing population places ever-

increasing demands on the spatial arrangement of cities and land use. Therefore, it is important to quantify the extent of urban growth in terms of demography at the metropolitan level and thus assess the dynamics of growth. The results thus provide evidence to help explain the process of urban development and also help urbanistically consider the potential risks of urban sprawl and development highlight inefficient. This paper deals with the evaluation of the centers of the Hradec Kralove - Pardubice agglomeration, a unique metropolitan area in the Czech Republic.

Keywords

Urban – sprawl, urban development, agglomeration,

1. Introduction

Since the middle of the 20th century, the dynamics of urban development has been gaining momentum on a global scale [1]. Economic activity, population growth and settlement patterns are phenomena that are associated with the process of spatial deconcentration, causing "urban-sprawl". These phenomena are particularly accelerating in the context of rapid social development and economic progress [2]. Nevertheless, "urban-sprawl" is an increasingly common phenomenon in most major cities around the world [3]. This fact is important because it contradicts the classification of the developmental stages of large cities, which were proposed in 1982 by

van den Berg, Drewett, Klassen, Russia and Vijverberg. According to this classification, it follows the suburbanization urbanization phase, then develops in the deurbanization phase and can achieve reurbanization. However, as the example of many cities proves, suburbanization, transitioning to "urban-sprawl" as a spatial phenomenon can be found in each of the phases defined in the model of van den Berg et al. [4]. Global urbanization research has been conducted in Europe and a suburbanization model in Central and Eastern Europe (CEE) has been observed. The result of that research is the importance of distinguishing the unique nature of suburbanisation in Central and Eastern Europe in terms of development, dynamism and spatial form [5 the Czech Republic belongs to this area of the Central Europe. This text can be taken into account as an example of showing the background of the phenomenon "Urban - sprawl" which acts as an aspect detrimental to sustainable urban development - the example of the Hradec - Pardubice agglomeration.

"Urban-sprawl" means uncoordinated and spontaneous suburban development without respecting the principles of proper management of the environment. Urban sprawl is characterized by the development of isolated areas with residential or commercial functions without links to technical, transport or social infrastructure and with serious impacts on the physical and social environment of metropolitan regions [6].

2. Data and methods

For the purposes of the research, a variety of spatial data were used, which had to be supplemented by demographic data. The basis for the analysis of demographic development was statistical data from the Czech Statistical Office, data from strategic documents, studies and other development documents relevant to the





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area, as well as public information on the cities of Pardubice and Hradec Kralove. The development of the population in the period of conducting the census in the Czech Republic, in the years 2001 to 2013, was evaluated. Further analyses will be carried out in the future in 2025.

As of 31 December 2013, a total of 335,118 inhabitants lived in the defined area. This is an area with a significant concentration of population, as the population density was 288 inhabitants / km2, which is twice the value compared to the average population density of the Czech Republic. The territory of the Hradec-Pardubice metropolitan area consists of 8 districts of municipalities with extended powers (ORP) and 13 districts of municipalities with an authorized municipal office (POÚ). There are 145 municipalities in the area, of which 14 municipalities with city status. The most populous settlements are the cores of the Hradec Kralove metropolitan area (92,904 inhabitants) and Pardubice (89,432 inhabitants), followed by the towns of Chrudim (22,996 inhabitants), Jaromer (12,594 inhabitants) and Přelouc (9,019 inhabitants). The population of the agglomeration can be characterized as growing in the period 2002 - 2013, in this period there was an increase by more than 7 thousand in the area. population, mainly due to migration [7]. Suburbanization tendencies in the territory are obvious. During the period under review, there was a decrease in the number of inhabitants in large settlements - Hradec Kralove, Jaromer and Chrudim. Pardubice shows a fluctuating development. On the contrary, there is an increase in the number of inhabitants in smaller municipalities in the hinterland of cities; a significant development of the population is recorded in the area between Hradec Kralove and Pardubice. The development of the population of the area and its cores is shown in Figure1 and Figure 2.

Fig. 1: Development of the population in the Hradec Kralove - Pardubice agglomeration in the years 2001-2013.

Fig. 2: Development of the population in Hradec Kralove and Pardubice agglomeration in the years 2001-2013.

The data were supplemented by detailed data from the Topographic Database of the Czech Republic (DATA2020), showing the state of spatial changes in eight thematic groups influencing the spatial development of cities (administrative boundaries, water supply, transport, settlements, buildings, geography, vegetation, elevation).

Data from the Spatial Planning Portal of the Czech Republic (UUR) and the Ministry of Regional Development (MRD) were used to determine spatial and functional changes in the Hradec Kralove-Pardubice agglomeration.

The paper also uses statistical data (demographic - see above, economic and spatial) derived from the Czech Statistical Office (CZSO) for the period 2000 - 2019. These data were used, inter alia, to determine the dynamics of change and construction activity in the Hradec - Pardubice agglomeration.

The typology of suburbanization was determined, which was based on the spatial relationships between the two nuclei of the agglomeration (Pardubice and Hradec Kralove). The Hradec Kralove - Pardubice settlement and industrial agglomeration formed an important industrial and agricultural area in the center of gravity of the East Bohemian Region. At present, the extensive development of the tertiary sphere and the importance of both regional cities set the pace for the development of logistics centers accompanied by the development of transport infrastructure, as well as the development of higher civic amenities. The whole organism of the agglomeration is complemented by recreational functions in the zones of biologically and landscape-valuable area. Due to their size, they become development poles due to their background, within which significant resources are created, which results in the development of not only the agglomeration itself. The specific position of both regional cities of Hradec Kralove and Pardubice and their metropolitan areas create a very strong bipolar settlement regional agglomeration within the Czech Republic. Based on the established typology, the hypothesis was

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established that, assuming sophisticated strategic planning not only in core cities, but also in the entire agglomeration, the negative impact of suburbanization processes such as "Urban-spray" can be significantly affected.

3. Conclusion

Spatial development of the territory can be recorded at all scales from states and continental regions to parts of cities or individual settlements within an agglomeration [8]. From the research it was found that disparities in the use of the Hradec - Pardubice agglomeration occur mainly because on the one hand some areas are overused (more than their carrying capacity) and other areas are not used, or are used insufficiently or in a different way than their potential. Some of them can be mentioned for clarity

Extensive construction of the area by residential buildings or logistics areas on a "green meadow" in the hinterland of the Hradec Kralove-Pardubice agglomeration has increased significantly in the last 19 years. Suburbanization and urban sprawl consumes parts of the landscape that could be used as agricultural land or forest. These effects destroy the natural environment, including its ecological function. Large built-up areas can cause a change in the microclimate, require connection to engineering networks with induced operating costs and change the character of the landscape (usually for the worse). A sustainable alternative to extensive landscape development is a more efficient use of the built-up area, especially localities or areas that have lost their function in the area (abandoned production or military areas).

Excessive intensity of use of the built-up area is recorded in attractive parts of cities, especially their centers, where indoor blocks are built, there is an effort to increase the level of development of new buildings or roofs by installing additional apartments and offices. The consequence of the pressure for excessive intensification of use in such cases is the deterioration of the microclimate by an increase in dust, dry air or the overheating of urban spaces in the summer months, mainly due to devastation or the absence of greenery. A frequent problem in excessively paved parts of cities is the flooding of sewers during torrential rains, due to the absence of retention areas. The increase in the number of users of such parts of cities further worsens the traffic situation, the problem with parking spaces is growing. Last but not least, the aesthetic quality of the place is disturbed [6,8]. Secondly, the attractiveness of the area, which was the primary cause of excessive land use, may deteriorate, especially this phenomenon can be observed in the historic centers of both core cities. A frequently cited sustainable alternative to excessive concentration in centers is polycentric development, i.e. development in other centers that will attract some investors and visitors.

Another evidence of ongoing suburbanization within the intermediate area of the agglomeration is the municipality

of Vysoka nad Labem. In this village, which is closely adjacent to the core town of Hradec Kralove, but is located in the Pardubice region, the number of inhabitants has increased by as much as 600 inhabitants since 2001, i.e. by half. Other municipalities with such a large increase in population are Byst, Opatovice nad Labem and Trebechovice pod Orebem. This increase is due to the existence of the agglomeration itself, which brings with it not only positives but also negatives.

The most loss-making localities in Hradec Kralove are historically the most populous districts - Moravske Předměsti, Slezske predmesti, Prazske predmesti and the city center itself, the most significant outflow of population is in these localities, they leave for surrounding municipalities or parts of Trebes, Malsovice, Svinary and Roudnicka. This trend is also recorded in Pardubice, which is facing an outflow of population from large housing estates such as Polabiny, Dukla, Karlovina and Dubina.

The influx of new population into the surrounding municipalities or suburban areas brings with it pitfalls in the form of a social environment in which old settlers encounter newcomers, often experiencing problems in newly built residential areas with dysfunctional public infrastructure (public lighting, public spaces or collection points for waste separation). The advantages of the agglomeration include cheaper services, quick access by car or public transport and often cheaper housing. The use of civic amenities is at a high level in both core cities, as there are about 110,000 people in core cities on week days. Based on this, the effort of both core cities to cover various requirements in the tertiary sphere, which leads to the attractiveness of the agglomeration as a whole, is obvious. For the purpose of outlining the problem of suburbanization processes, it is possible to use Fig. 3, recreational sites are highlighted here. Their situation is influenced not only by the strong position of the foci of development, which are the core cities, but also by the intermediate space itself, which is an economically very valuable area in this agglomeration.

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Fig. 3: Overview of the main development localities monitored for a long time in the zoning plans of towns and municipalities in the Hradec Kralove-Pardubice agglomeration.( red - development areas, housing; purple- development areas, civic amenities; yellow - development areas, sports, recreation and industry (dark yellow)).

In conclusion, future research hopes to find an acceptable solution that will allow the research process to be easy and re-created and can be applied to other urban agglomerations in Central and Eastern Europe.

Acknowledgements

This work was supported by funds for the Conceptual Development of Science of the VSB – Technical University of Ostrava, Research and Innovation for 2020.

References

[1] KNOX, P.l., MCCARTHY, l.M. (2012). Urbanization: An introduction to urban geography (3rd ed.) Harlow, Pearson.

[2] ANGEL, S., SHEPPARD, S. C., & CIVCO, D. L. (2005). The dynamics of global urban expansion. Washington D.C: Department of Transport and Urban Development, The World Bank.

[3] ANGEL, S., PARENT, J., CIVCO, D. L., BLEI, A., & POTERE, D. (2011). The dimensions of global urban

expansion: Estimates and projections for all countries, 2000–2050. Progress in Planning, 75(2), 53–107. https://doi.org/10.1016/j.progress.2011.04.001.

[4] KRZYSZTOFIK, R., KANTOR-PIETRAGA, I., RUNGE, A., & SPÓRNA, T. (2017). Is the suburbanisation stage always important in the transformation of large urban agglomerations? The case of the Katowice conurbation. Geographia Polonica, 90(2), 71–85. https://doi.org/ 10.7163/GPol.008.

[5] MANTEY, D., & SUDRA, P. (2018). Types of suburbs in post-socialist Poland and their potential for creating public spaces. Cities, 88, 209–221. https://doi.org/10.1016/j. cities.2018.11.001.

[6] HNILICKA, P. Settlement slurry: questions about the suburban construction of colonies of family houses. 2., add. Brno: Host, 2012, 207 pp. Urbanism to packet (Guest). ISBN 978-807-2945-924.

[7] B. BURCIN, Z CERMAK, T. KUCERA, Forecast of the development of the number and sexual and age structure of the population of the statutory city of Pardubice for the period 2013-2050, Prague 2014.

[8] MUSIL J., Sociology of the Contemporary City, Svoboda Publishing House, Prague, 1967.

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METHODOLOGY OF GREEN ACUPUNCTURE AS A TOOL FOR SUSTAINABLE STRATEGY IN URBAN PLANNING

Adéla BRÁZDOVÁ1,2, Barbara VOJVODÍKOVÁ1,2, Jiří KUPKA3

1IURS – Institute for Sustainable Development of Settlements

Bulharská 1424/25, Ostrava, Czech Republic 2Department of Building Materials and Diagnostics of Structures, Faculty of Civil engineering,

Technical University of Ostrava, 17. listopadu 2172/15, Ostrava, Czech Republic 3Department of Environmental Engineering, Faculty of Mining and Geology, Technical University of Ostrava,

17. listopadu 2172/15, Ostrava, Czech Republic


Abstract. This article deals with current problems of large European cities. Finding suitable spots for greenery planting in very dense urban areas is not only current problems, but also a challenge for the future sustainability of cities and urban climate resistance. This is the core of the international project SALUTE4CE - Integrated environmental management of small green spots in functional urban areas, following the idea of acupuncture (project index number: CE1472) within the Interreg CENTRAL EUROPE Programme. Greening principles of abandoned areas are based on the Green Acupuncture strategy. In each urbanized space it is possible to find sites which the proposed Green acupuncture method can be applied to. How to find areas or places where greenery planting can be realized? This article presents key criteria which are further assessed in the GACUM model. Methodology was verified in Liptovský Mikuláš which was chosen as one of the model towns within the project in 2019.

Keywords

Urban greenery, green acupuncture, sustainable city, urban climate resistance

1. Introduction

One of the current problems of larger European cities is the task of increasing of the proportion of green areas in their built-up areas as much as possible. Greenery in general is, among other things, a necessary condition for urban climate resistance and sustainability.

Urban areas with their high density of buildings and roads mostly no longer allows for introduction of the green areas in terms of parks, playgrounds, etc. (so-called urban greenery). How to find areas or places where greenery planting can be realized in such very dense urban areas?

2. Methods

This issue is solved within the international project SALUTE4CE - Integrated environmental management of small green spots in functional urban areas, following the idea of acupuncture (project index number: CE1472) within the Interreg CENTRAL EUROPE Programme.

Due to the expansiveness of contemporary cities, localities have appeared in urbanized area that have lost their importance and function, therefore they can be considered as a potential source of areas suitable for placing greenery - the so-called potential green acupuncture spots (PAS). The Green Acupuncture Model (GACUM) is a multi-criteria tool for the search for potential green acupuncture spots (PAS) and subsequent evaluation of green acupuncture spots (AS). PAS and AS are small localities (with an area of typically up to 0.6 ha). Green acupuncture is a method that allows the conversion of potential green acupuncture spots to green areas, which serve to reduce a number of adverse effects and thus have an impact on the microclimate of the environment and therefore also on residents of the settlement.


mailto:[email protected],


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3. Results

Due to solving the international project SALUTE4CE - Integrated environmental management of small green spots in functional urban areas, following the idea of acupuncture was specified key criteria. In each urbanized space it is possible to find sites in which the Green acupuncture method can be applied to and where suitable strategy can be selected in cooperation with stakeholders (investors, public, city authorities, etc.).

Here are some criteria which are further assessed in the GACUM model, and will be elaborated in bigger detail in the article:

• Location criteria – the size of the area, its location, attractiveness and the relation to the surroundings are significant.

- The size of the area (should not be over 0.6 ha)

- Location inside FUA (functional urban area) – The area needs to be located in FUA [3]

- Delimitation of assessment “borders“, whether this place (acupuncture spot – AS) is the main problem of the given area -> Is planting greenery here going to solve the problem? [1] [4]

• Perspective criteria – definition of broader relations of the given area in the viewpoint of future perspective.

- Assessment of the area in terms of the availability of public greenery [4]

- Determined (estimated) appropriate/minimal number of ASs to achieve improvement [3]

- Determined preliminary target number of ASs to be developed by the investor and placed into in the action plan

• Criteria of PAS/AS register existence

- Determined preliminary target number of ASs to be developed by the investor and placed into in the action [1]

- List of all available PASes in the city and FUA

- Selection of ASes based on previous assessment [3]

• Criteria of appropriate solution

- Suitability of the solution for the area

- Present (existing) state of the area

- Prediction of the changes in the state after application of tools [2] [5]

4. Conclusion

In 2019, Liptovský Mikuláš was chosen as one of the model towns within the project. To verify the proposed methodology for greening the city (GA), four model areas were selected in the territory of Liptovský Mikuláš (plots near the school, city centre, facades in the area with densified buildings and courtyard spaces). Different scenarios for green acupuncture were proposed for each of these locations.

The article is going to describe the application of the GACUM model criteria on the territory of Liptovský Mikuláš and the assessment of the selected model areas’ suitability.

Acknowledgements

This article was prepared thanks to support from Interreg CENTRAL EUROPE Programme for opportunity to participation in international project SALUTE4CE - Integrated environmental management of small green spots in functional urban areas, following the idea of acupuncture (project index number: CE1472).

References

[1] YOON, E. J.., B. KIM and D. K. LEE. Multi-

objective planning model for urban greening based

on optimization algorithms. In: Urban Forestry &

Urban Greening, 2019, vol. 40, pp. 183-194. ISSN

1618-8667. DOI: 10.1016/j.ufug.2019.01.004.

[2] ZHANG, L., D. ZHICHAO, L. LIANG, Y. ZHANG,

Q. MENG, J. WANG and S. MATTHEOS. Thermal

behavior of a vertical green facade and its impact on

the indoor and outdoor thermal environment. In:

Energy and Buldings, 2019, vol. 204, pp. 1-114.

ISSN 378-7788. DOI:

10.1016/j.enbuild.2019.109502.

[3] HAN, M.J.N, M.J. KIM. Green Environments and

Happiness level in Housing Areas toward a

Sustainable Life. In: Sustainability, 2019, vol. 11

(17), 4768, pp. 1-18, EISSN 271-1050. DOI:

10.3390/su11174768.

[4] ELSADEK, M., B. LIU and Z. LIAN. Green façades: Their contribution to stress recovery and well-being

in high-density cities. In: Urban Forestry & Urban

Greening, 2019, vol. 46, pp. 1-10. ISSN 618-8667.

DOI: 10.1016/j.ufug.2019.126446.

[5] DJEDJIG, R., R. BELARBI and E. BOZONNET.

Green wall impacts inside and outside buildings:

experimental study. In: Energy Procedia, 2017, vol.

139, pp. 578-583. ISSN 1876-6102. DOI:

10.1016/j.egypro.2017.11.256.

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OCCURRENCE OF VEHICLES BUNCHES IN TRAFFIC FLOW

Ivana MAHDALOVA1, Vaclav SKVAIN1

1Department of Transport Constructions, Faculty of Civil Engineering, VSB-Technical University of Ostrava, Ludvika Podeste 1875/17, Ostrava-Poruba, Czech Republic


Abstract. The paper deals with the occurrence of vehicles bunches in the traffic flow based on the monitoring of actual traffic on roads in the Czech Republic. The occurrence of vehicles bunches in the traffic flow, i.e. groups of vehicles travelling consecutively with minimal headways, has an impact on traffic safety and may affects the capacity of an intersection or weaving segment of a road. It has been demonstrated previously that this phenomenon is a natural feature of the traffic flow. Our research confirmed the basic hypothesis that even under relatively low traffic volumes, some of the drivers do not keep the desirable safe distance between following vehicles. The paper shows some of the details found during the observation of this phenomenon.

Keywords

Vehicles bunches, following vehicles, safety distance, time headway, traffic flow.

1. Introduction

It is assumed that drivers on low traffic volume road are not affected by other vehicles and may freely choose their speed by their selection. Nevertheless, vehicles bunches are formed on such roads. These bunches represent groups of following vehicles travelling in one direction with relatively small time headways. Based on observation of real traffic, the occurrence of vehicles bunches can be statistically expressed. Their presence in traffic flow may negatively affect the capacity of intersections on the route and the safety. Drivers travelling in the “follow - up” mode may feel raising nervousness and aggressiveness. That can be a cause of risky overtaking or source of traffic accidents.

The problems of vehicles bunches formation on roads have

already been discussed by other researchers [1], [2]. We can talk about the vehicles bunch when following vehicles come close to one another and the follower, due to impossibility of overtaking the leading vehicle, is entering the “follow - up” mode. This “follow - up” mode is also used in many psycho - physical traffic models, such as Wiedemann, Gipps or Fritzche [3] and depends e.g. on minimal or comfortable time gap between successive vehicles, which is expressed as a time headway. For example, the Australian study [4] states the threshold value of driver influence in “follow - up” mode as ≤4 s of the time headway. It was also shown, that the formation of vehicles bunches can be defined as a natural feature of the traffic flow [5].

2. Basic Hypothesis

The article describes statistical relationship found out between the number of vehicles travelling in vehicles bunches and the current traffic flow in conditions of the Czech Republic. The following hypotheses were tested:

1. Bunching of the vehicles is a natural feature of the traffic stream.

2. Vehicles bunches are formed even at minimum traffic flows.

3. With increasing traffic flow also increases the portion of vehicles travelling in vehicles bunches.

3. Methodology

The article focuses on the issues with occurrence of vehicles bunches in traffic stream on undivided two lane roads in the Czech Republic under low or moderate traffic volume.



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3.1. Time headway and vehicles bunches

Ideally, the safety time gaps (headways) should be maintained between successive vehicles in the traffic stream. Different countries have a little bit various rules of legal or recommended safety time distance [6]. Usually the recommended safety time gap is given by 2 seconds.

3.2 Data collection and analysis

On observed segments of two lane roads with low or moderate traffic volume were made a series of a video records of the traffic. The records were made at different day period (morning and afternoon peak, midmorning off - peak) so that all maximum and minimum traffic volumes were captured on each monitored roads. The records were manually evaluated with the usage of chronometer afterwards. The time gaps between successive vehicles in the traffic stream were recorded and statistically evaluated by standard MS Excel tools.


From the observation of the traffic it is evident that with raising traffic volume the number of vehicles travelling in bunches also increases– see Fig. 1. Likewise, the proportion of the vehicles travelling in the “follow - up” mode is also increasing.

Fig. 1: Percentage proportion of bunched vehicles depending on the traffic volume (in one direction).

5. Conclusion

The knowledge of the distribution of vehicles bunches in the traffic stream is necessary for appropriate settings of microscopic dynamic simulation in traffic modelling. It is also useful for getting more precise outputs of capacity assessments in traffic engineering.

• The assumption that the formation of vehicles bunches is a natural feature of the traffic stream has been confirmed.

• Vehicles bunches are formed even at minimum traffic flows. It was already found that at a minimal traffic flow 100 veh/h (LOS A), more than quarter of vehicles (26 %) travelled in bunches.

• It was confirmed that as the traffic flow is increasing, the portion of vehicles travelling in vehicles bunches is also increasing. There was found a relatively visible statistical dependence between these parameters (numbers of vehicles travelling in bunches and traffic flow). Similarly to this, the proportion of vehicles travelling in the “follow - up” mode is increasing.

From the records it is obvious that though drivers may respect the recommended safe time gaps between successive vehicles, they do not always do so. With increasing traffic flow, there is apparent growth of number of critical low time headway in formed vehicles bunches (time headways in values ≤1 s). At such as time headways below 1 second the drivers are not able to adequately react to sudden maneuvers of preceding vehicle (unexpected braking for example) that may result in mutual collisions or traffic accidents. Under the conditions of moderate or high traffic volumes and greater portion of vehicles travelling in bunches, we may logically expect higher chance of multiple vehicles collisions (chain rear end accidents for example).

Acknowledgements

The work was supported from sources for conceptual development of research, development and innovations for 2020 at the VSB-Technical University of Ostrava which were granted by the Ministry of Education, Youths and Sports of the Czech Republic.

References

[1] AKÇELIK, R. Gap acceptance modeling by traffic signal analogy. Traffic Engineering and Control. 1994, vol. 35, iss. 9, pp. 498–506. Online available http://www.sidrasolutions.com/documents/akcelik_1994_tec35-9.pdf.

[2] TROUTBECK, R. J. Evaluating the Performance of a Roundabout. 1989, TL Special Report No. 45, Australian Road Research Board Transport Research Ltd, Vermont South, Australia. 57 p.

[3] OLSTAM, J. J. and A. TAPANI. Comparison of Car-following models. 2004, Project code 40503 and 40485, VTI meddelande 960A, Swedish National Road and Transport Research Institute, Linköping, Sweden. 36 p. Online available https://www.diva-portal.org/smash/get/diva2:673977/FULLTEXT01.pdf.

[4] MetroCount. 85th Percentile Speed – Investigating Modern Use. 2014, MetroCount, Australia. Retrieved

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from https://metrocount.com/85th-percentile-speed-investigating-modern-use/.

[5] HOLCNER, P. Modelovani a simulace dopravniho proudu [Modeling and Simulation of Traffic Flow]. 2012, Habilitation Thesis, Brno University of Technology, Czech Republic. 37 p. (in Czech). Online available http://www.vutium.vutbr.cz/tituly/pdf/ukazka/978-80-214-4590-1.pdf.

[6] VOGEL, K. A comparison of headway and time to collision as safety indicators. Accident Analysis and Prevention. 2003, vol. 35, iss. 3, pp. 427–433. ISSN 0001-4575. DOI: 10.1016/50001 -4575(02)00022-2. Online available https://www.sciencedirect.com/science/article/pii/S0001457502000222?via%3Dihub.

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GEOMETRIC ANALYSIS OF TURBO ROUNDABOUT ENTRANCE

Jan PETRU1, Vladislav KRIVDA1

1Department of Transport Constructions, Faculty of Civil Engineering, VSB – Technical University of Ostrava, 17. listopadu 2172/15, Ostrava, the Czech Republic


Abstract. Turbo roundabouts are a modern type of intersections that gradually replace two-lane and multi-lane roundabouts. It is a special roundabout layout with two or more lanes. In comparison to normal roundabouts with two or more lanes, there should be ensured greater safety and capacity of traffic. The article focuses on geometrical layout of turbo roundabouts, especially in the place of its entrance. The Czech and foreign regulations are analysed. The procedures for the design of turbo roundabouts and geometry of its entrance are described there. On the basis of research carried out in the Czech Republic and abroad (the Netherlands, Slovenia, Slovakia, Poland, Germany, Hungary) the geometrical layout of turbo roundabouts and efficiency of construction work at the entrance to the turbo roundabout are evaluated. This includes especially the physical separation of lanes. Data obtained using counting devices, radars, various types of video cameras and drones recording turbo roundabouts at its entrance were also analysed. For evaluation of the efficiency of the geometry of the entrance the conflict situations were recorded and subsequently evaluated.

Keywords

Conflict Situation, construction elements, drone, geometry, turbo roundabouts.

1. Introduction

In the Czech Republic and also abroad turbo roundabouts are gradually being designed and realized. Turbo roundabout [1] is a special type of a roundabout that has two or more spirally designed lanes on the circular lane. The principle of the geometrical layout of the intersection is to ensure the vehicles smooth passage via the intersection from the entrance through the circular lane to the exit in one lane without the need to change the lanes.

Due to a specific geometrical layout [2] this type of intersection provides higher capacity in comparison to a one-lane roundabout and at the same time a higher degree of safety as two-lane roundabouts [3].

An important element on spirally organized lanes is prevention of intertwining of vehicles and prevention of possible conflict situations [4] with the help of physical separation of lanes. Inevitability of this physical element for the proper functioning of the intersection is, however, subject of many discussions [5].

The physical separation of lanes and the design of geometry have a major influence on the entrance of the vehicle into the turbo roundabout. It is very important to guide the vehicles into the required lanes in front of the roundabout. The subsequent trajectory of the vehicle in the place of entrance into the intersection has a great influence on the overall passage of the vehicle via the turbo roundabout. The consequence of it is whether there will arise conflict situations, of what type and what influence they will have on the efficiency and safety of this particular intersection.

2. Geometry and Division of Turbo Roundabouts

Turbo roundabouts were developed by L. G. H. Fortuijn from the Netherlands in 1990. The basic design of the intersection geometry is sc. turbo block, which represents a set of lines used for the design of the lanes on the circular lane. The turbo block is created from interconnected arcs of given radii, their connection points and mutually rotated centres are placed on rotated translation axis. The intersection can be created of one or two, or two or three lanes. The new lane is formed in the place of the entrance and it adjoins the continuous lane of the circular lane on the inner side. New lanes are designed at the main entrances in dominant directions of the lanes (Fig. 1).



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Thus, the directions of the dominant lanes become the basic criterion for the selection of the suitable type of the turbo roundabout.

Fig. 1: Turbo block with translation axis and radii of individual circles [2].

3. Problematic Situations at Turbo Roundabouts

On Turbo Roundabout in the place of the entrance there arise several possible types of conflict situations. One of the examples is Shortening of the driving lane (crossing from outer into inner lane at the entrance to the turbo roundabout). The vehicles that are on the driving lane of the turbo roundabout are shortening their passage by a sharp manoeuvre. An undesired shortening is shown on (Fig. 2) in the parts 1-3. • Part 1 – the vehicle 1 should continue in its lane as

indicated by the dashed arrow. The vehicle 1 suddenly brakes and changes its direction into the inner lane. Vehicle 2 arrives at the entrance of the turbo roundabout.

• Part 2 – after sudden braking the vehicle 1 passes with the front and the rear axles the dividing element of the intersection. Vehicle 2 slows down and changes its direction into the inner lane.

• Part 3 – vehicle 1 continues in the inner lane and leaves the turbo roundabout. Vehicle 2 continues in the inner lane and then leaves the turbo roundabout. After leaving the turbo roundabout both vehicles go from the left into the right lane. If they stayed in the outer lane (shown by the dot and dashed arrow), they would leave the turbo roundabout directly from the right lane.

Fig. 2: Turbo block with translation axis and radii of individual circles [2].

4. Analysis of the Picture in the Place of Entrance

Program DATA FROM SKY [6] was used for the analysis of the pictures from the drone. An example of the usage of the program is shown in (Fig. 3). The movement of the vehicles, its trajectories, the speed at the entrance to the intersection, the gap between the vehicles, safety analysis, etc. were analysed in the program.

Fig. 3: Analysis of the video from the drone at the turbo roundabout in Ceske Budejovice with the help of the DATA FROM SKY program.

5. Conclusion

The physical separation of lanes in front of the intersection and on the circular lane of the roundabout has a significant influence on the safety of the traffic. As mentioned in the results of our measurements the physical separation of lanes has a significant influence on the safety, efficiency of the intersection and it also has a psychological function. Unfortunately, this physical element can be found only on 5 intersections in our country. With the newly designed intersections it is not considered due to the lack of knowledge during the design, investigation, or negative attitude of the administrator of the road.

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Acknowledgements

The works were supported from sources for conceptual development of research, development and innovations for 2020 at the VSB-Technical University of Ostrava which were granted by the Ministry of Education, Youths and Sports of the Czech Republic.

References

[1] TOLLAZZI, T., S. TURNSEK and M. RENCELJ. Slovenian experiences with „Turbo-Roundabouts”. 2. Mostar, Bosna i Hercegovina: Građevinski fakultet Sveučilište u Mostaru, 2012. ISSN 2232-9080.

[2] TP 14/2015 Projektovanie turbo-okružných križovatiek. MDVR SR, 2015.

[3] GIUFFRÈ, O., A. GRANA, S. MARINO and M. RENÇELJ. Comparing Performances of Turbo-roundabouts and Double-lane Roundabouts: "Turbo", "Flower", "Target" and "Four-Flyover" Roundabout. Modern Applied Science. 2012, vol. 6 iss. 10. DOI: 10.5539/mas.v6n10p70. ISSN 1913-1852.

[4] KRIVDA, V., I. MAHDALOVA and J. PETRU. Use of Video Analysis of Conflict Situations for Monitoring of Traffic on Urban Road Influenced by Parallel Parking. Communications. Slovakia: University of Zilina, 2013, vol. 15 iss. 3, pp. 118-125. ISSN 1335-4205.

[5] PETRU, J., KRIVDA, V., MAHDALOVA, I. and K. ZITNIKOVA. Different Types of Materials for the Physical Separation of Lanes of the Turbo-Roundabouts. 16th International Multidisciplinary Scientific GeoConference SGEM 2016: Green Buildings Technologies and Materials. Albena: BULGARIA (June/July 2016). Book 6, Vol. 2, 2016, pp. 83-90. ISBN 978-619-7105-69-8. ISSN 1314-2704. DOI: 10.5593/SGEM2016/B62/S26.012

[6] DATA FROM SKY [online]. [cit. 2020-01-13]. Available from: https://ai.datafromsky.com/

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RESEARCH ON ADAPTATION SOLUTIONS TO HIGH TIDE FOR

POOR HOUSING IN HO CHI MINH CITY

Le-Minh NGO1, Duy Anh TRINH 2, Hai-Yen HOANG 3

1 Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam

2 University of Architecture Ho Chi Minh City, Viet Nam

3 Faculty of Architecture- Art, Ho Chi Minh City University of Technology (HUTECH), 475A Dien Bien Phu Street, 25

Ward, Binh Thanh District, Ho Chi Minh City, Vietnam

[email protected]

Abstract: Ho Chi Minh City (HCMC) is Vietnam’s largest city in terms of population and economy, the

second in area, and one of the most important economic,

political, cultural and educational centres of Vietnam.

Currently, HCMC is a unique urban type in Vietnam. With

the rapid population growth rate, infrastructure has not

been able to meet planned upgrades overall, urban

planning is still inadequate, and part of the population’s awareness of environmental protection is still weak.

HCMC is now facing frequent flooding problems. The

main reason is due to global climate change, causing

saline water to intrude deeply into the land and local

climate change causes high tide levels. With the evolution

of climate change, HCMC is on the list of 10 cities in the

world threatened by rising sea level risks, especially in

suburbs and some low-lying areas of the city. According

to the estimates of the United Nations, by 2100, the sea

level will rise by more than 1 meter and nearly 20% of

HCMC's area will be flooded.

The phenomenon of high tide occurs during a certain

period of time by being affected by the Moon and the Sun

whenever the Earth spins for a day. At that time, sea and

river water levels will rise and fall, and when these levels

return to normal, the tide will pass. High tide is the

oscillation of the highest and largest level of tide. Ho Chi

Minh City has a high density of rivers and canals, so it is

often strongly affected by the high tide. In addition,

human activities to the streams like river accretion and

encroachment, sand exploitation, building houses close to

river banks, and so on, preventing the flow of rivers and

canals, which causes the tide to rise and fall

uncontrollably. The impacts of high tide on the residential

low-lying areas in HCM city are becoming more and

more obvious and causing many difficulties for people's

lives, especially housing of poor people. Understanding,

investigating the current situation and assessing the

impact of high tide on poor housing in Ho Chi Minh City

is very necessary. Thereby providing solutions for poor

housing to adapt to the high tide, aiming to improve the

quality of life of poor people living along the canals of

Ho Chi Minh City.

Regarding the Research Methodology, this paper is a

qualitative study using a mixed method approach

including Method of Synthesis & Materials Comparison,

Questionnaires, Interviews, and Observations. Synthesis

& Materials Comparison to be applied to show the

current situation analysis table, to build a database of

high tide phenomenon in District 4, Ho Chi Minh City.

The collection of documents and data is conducted

directly at the agencies of the city, the Research Institutes,

Ho Chi Minh City Planning and Architecture

Department, Ho Chi Minh City Construction Department,

the Southern Construction Planning Institute – the

Construction Ministry, and Urban Management District 4

Department.

The method used the Questionnaire and Interview to

investigate and collect information about the impact of

high tide to flood on people houses in the study area. The

interview will collect information about people's

awareness for flooding due to high tide on Ton Tat Thuyet

road along Kenh Te canal, District 4, HCMC. Since then,

combined with the observation method to select the areas

that need to be researched particularly, based on different

criteria including housing location in the areas be

affected by flooding, the extent flood and flood intensity.

Then combining the detailed data from the survey with

the observation will give the results by the population

distribution maps, the areas are affected by flooding due

to the high tide.

This research method can be applied and implemented

for research on housing adapting to climate change and

sea level rise. Especially those researching types of

houses for resettlement, houses for the poor people, or


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houses for migrants in suburban areas of Ho Chi Minh

City.

The expected result of this research is to provide solutions

for poor housing in District 4, Ho Chi Minh City. They

are: Flexible space division solutions; Solutions to use

floating buoys to prevent high tide from the canals banks;

Solutions to use gates with tide walls; Solutions of

treating domestic wastewater, reducing pollution of canal

banks; Solution of using garbage collection grid at each

residential area. Finding solutions to adapt to high tide

for poor houses in Ho Chi Minh City aims to sustainable

development for poor people in the future.

Keywords

Poor housing, adaptation measures, climate change,

high tide, Ho Chi Minh City.

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URBANIZATION OF PERI-URBAN AREA - THE PROBLEM OF

MAJOR ASIAN CITIES. CASE STUDY OF NHA BE DISTRICT,

HO CHI MINH CITY

Le-Minh NGO1, Phuong-Thao HOANG-THI 2

1 Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam

2 National Cheng Kung University, Taiwan

[email protected]

Abstract: Today, under the impact of strong

urbanization from urban centers, peri-urban areas are

strongly affected and there are many changes in both

structure and characteristics. So far, although there has

been no consensus on the definition of peri-urban areas,

it is increasingly recognized that urban and rural

characteristics tend to coexist in cities and to intersect

with each other. This is in part because these areas tend

to expand, develop horizontally, and they are considered

as extensions of major urban areas. In addition, due to

the dispersal of the population and the spread of

employment spreading to newly developed urban areas,

urbanization (Peri-urbanization) is becoming

increasingly common and a challenge. New knowledge in

the context of Asian cities. Major Asian cities are in

constant need of land and natural resources, where

mechanical population growth and urban development

are leading to the process of suburban expansion. On

average, the population of Asian cities is growing by

more than 45 million people each year, resulting in the

conversion of more than 10 km2 of agricultural land to

urban use. Case of Tp. In Ho Chi Minh City, the latest

statistics in 2019 show that the population of Ho Chi

Minh City is increasing by 1 million people every 5 years.

This means that each year, HCMC receives an average of

200,000 new residents, equivalent to a small urban area.

The areas for expansion and conversion of functions

mentioned above are located in peri-urban areas, which

are transition areas for urban and rural activities,

whether or not they will be interconnected by the

activities human action caused and was decisive in the

future. In fact, suburban areas play an important role in

urban areas. The suburban area is the main source of

natural resources, human resources, food and food for the

city and this value will increase under the impact of

climate change, the increase in energy costs. amount and

changing pattern of food consumption in the future.

Facing that challenge, the suburban area needs to make

specific changes to both maintain its traditional role and

respond to the rapid pace of urbanization today.

Therefore, in the coming situation, Asian cities should

actively promote the dissemination of Asian urban studies

and cooperation among Asian universities and research

institutions, even consult government, to ensure a

sustainable future in urban and rural areas.

This study selected Nha Be district, HCMC. Ho Chi Minh

as a typical example. Regarding the location of the study

area, Nha Be district is located 30km southeast of Ho Chi

Minh City, with an area of 100 km2, a population of

160,000 people, administrative units including Nha Be

Town, and Hiep Phuoc Communes, Long Thoi Commune,

Nhon Duc Commune, Phu Xuan Commune, Phuoc Kien

Commune, and Phuoc Loc commune. With the speed of

rapid urbanization in the last 10 years, Nha Be district is

facing a rapidly increasing population, new residential

areas and built public works complex which are changing

structure and image of a suburban district.

Along with the development in all aspects, the issue of

rapid urbanization in this locality in recent years has led

to many unsettling problems. Under the impact of climate

change (CC) in Ho Chi Minh City, especially in Nha Be

and Can Gio districts, new residential areas and houses

of local people are facing the risk of encroachment, even

relocation, greatly affects the existence and development

of residential areas. Some temporary solutions are

applied by localities such as raising the roadbed,

elevation of the foundation, building foundations

surrounding the house to prevent water, etc. However, due

to the rapid urbanization rate, the infrastructure system is

not synchronized, and has not kept pace with the

urbanization rate, many areas of low-lying terrain have

been flooded due to heavy rains and high tides.

This paper is a qualitative study using a mixed method

that includes the method of aggregating and comparing

data and expert methods. Summary and comparison of

data are applied to give a table of current situation

analysis, to build a database of urbanization phenomenon


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in Nha Be district, Ho Chi Minh City. The collection of

documents and data is conducted directly at the agencies

of the city, the Research Institutes, the Department of

Planning and Architecture of Ho Chi Minh City, The

Southern Institute For Spatial Planning (SISP), Ministry

Of Construction, Southern Irrigation Institute, and Nha

Be District Office of Urban Management. Based on the

summary of the impacts of urbanization on the houses of

the people in the study area, the graphic software is used

to show the data, the current status map of the population

distribution, the affected area. effects of inundation due to

climate change, and provide a forecasting model until

2100. The expert method is used to consult experts in the

fields of planning, architecture, and housing architecture.

Since then, forming a scientific and legal basis based on

practical experience for urbanization in the suburban

areas of Nha Be. This research method can be applied

and carried out for studies on housing planning adapting

to climate change, especially studies on resettlement

housing planning, housing for the poor, or housing of

migrants in Ho Chi Minh City.

The goal of the study is to provide a new perspective on

the prospects and challenges that this area faces in the

future, as well as the desire to receive the right attention

of the authorities and regulatory planning experts on

peri-urban area development in Vietnam.

Keywords

Urbanization, suburban area, Peri-Urbanization, Nha

Be District, Ho Chi Minh City, Asia.

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MODELLING AND OPTIMISATION OF THE DRINKING WATER SUPPLY NETWORK - A SYSTEM CASE STUDY FROM THE CZECH

REPUBLIC

Marek TEICHMANN1, Dagmar KUTA1, Stanislav ENDEL1, Natalie SZELIGOVA2, Frantisek KUDA1

1Department of Urban Engineering, Faculty of Civil Engineering, VSB – Technical University of Ostrava, Ludvika Podeste 1875/17, 708 00 Ostrava-Poruba, Czech Republic

2Department of Spatial Planning and the Environment, Karvina City Authority, Frystatska 72/1, 733 24 Karvina, Czech Republic


Abstract. In this study, we investigated the modelling and optimisation of drinking water supply system reliability in the village of Zaben, Czech Republic. An in-depth overview of the water supply network in the municipality, passport processing and accident and malfunction recording is provided based on data given by the owner and operator of the water mains as well as the data collected by our own field survey. Using the data processed from accident and failure reports in addition to water main documentation, the water supply network in Zaben was evaluated according to the failure modes and effects analysis method. Subsequently, individual water supply lines were classified based on their structural condition. In addition, a proposed plan for financing the reconstruction of the water supply mains in Zaben was created. As such, this study provides an overall assessment of the water supply network in Zaben alongside a proposed plan for structural restoration of the water supply system, which accounts for the theoretical service life of the system and the financial resources of the owner.

Keywords

Water pipes, structural integrity, failure modes.

1. Introduction

Drinking water supply systems have significant impacts on the quality of human life, health, and hygiene. As such, a high quality, well-managed and well-maintained drinking water supply system is a foundational component of

infrastructure for an urbanised area.

Fig. 1: Division of individual water lines in Zaben (lines A to G). Adapted by the authors from Mapy.cz.

However, in order to effectively operate this infrastructure, it is necessary to understand its structural condition and perform maintenance and repairs accordingly to extend the functional life of the system. It has been shown that careful coordination of planned, comprehensive maintenance and






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renewal of the system can prevent operational emergencies and reduce the need for unplanned interventions. [1, 2].

The village of Zaben is situated in the Moravian-Silesian Region. In particular, Zaben can be considered a suburban part of the city of Frydek-Mistek. In Zaben, according to the CZSO, there are 827 inhabitants as of 1 January 2017 and individual housing is dominant. The village lies on a flat plain at an altitude of 266 to 270 m above sea level and its total cadastral area is 3.35 km2. The construction of the water supply system began in 1981 and was completed in 1984. A schema of the water mains in Zaben is presented in Fig. 1.

2. Materials & Methods

2.1. Evaluation of Structural Conditions of the Water Network

The evaluation of the structural condition of the system is a qualitative analysis that identifies weaknesses in the system along with the causes and consequences of these weaknesses [5]. Tab. 1: Classification of condition for technical indicators – adapted

from [5].

Category Condition Description

K1 Very good

Optimal condition of the relevant TI. No

action is required to change this indicator.

No significant change in the value of the

indicator is expected in the long-term.

K2 Good

Low risk level of the relevant TI. No

technical measures are expected to be

required in the near future.

K3 Satisfactory

Average value of the relevant TI.

Immediate solutions are not required, but a

change in the value of the indicator can be

expected in the near future.

K4 Critical

Critical values of the relevant TI. Measures

should be planned or implemented to

resolve this state.

K5 Emergency

Undesirable or non-functional condition. A

solution is required as soon as possible to

ensure proper functioning with regards to

this TI.

Similar to the general FMEA (Failure Mode and Effects Analysis) method according to CSN IEC 812 (010675), structural condition evaluation considers the system as a whole as well as its individual elements [1]. Monitored elements are evaluated with regards to various risk areas, known as Tis (Technical indicator), and are then classified into the categories K1 to K5 based on condition or efficiency. This classification system has been previously defined and is defined by criteria and input data specific to each TI [5]. The definition of these categories is provided in Table 1. The water supply network was evaluated according to five TIs, specifically:

• TI1 – Age of the pipeline,

• TI2 – Failure rate,

• TI3 – Water loss,

• TI4 – Pressure ratio,

• TI5 – Water quality.

2.2. Plan of Funding for Water Main Renewal

We developed a plan for water main renewal based on the system wear, structural and technical condition, service life, total property value, total water supply value and total associated service value. To determine the time required to accumulate necessary funding for repairs, we began by assessing the theoretical life span of the water system based on previous studies. The basic wear percentage (PO) was calculated for the water mains of interest. For this calculation, the age of the infrastructure assets is essential. As such, we determined the age of the system as a weighted average based on the length and material of the various pipe segments to ensure accurate calculation of required funding. Calculation of the percentage of wear was based on the theoretical service life of the pipe material in the water supply network, which was a PVC pipeline with a 60-year life expectancy. The actual water supply in the village was built between 1981 and 1984, and it is therefore between 35 and 38 years old. Approximately 8% of the water main length has been repaired or replaced since construction. As such, the calculation of wear percentage considered the average overall age as 36.5 years [6]. Theoretical time for accumulation of funds (TDAP) in years is the calculated average time remaining before implementation of the renewal process is required, as renewal is required prior to the end of service life. Annual funds needed for reconstruction (RPPO) represents

the amount of funding that should be spent on regular

renewal of infrastructure assets to ensure their reliability,

functionality and sustainability. RPPO incorporates the

total value of the infrastructure, TDAP and the deadline by

which the system must be reconstructed.

3. Results & Discussion

3.1. Assessment of Structural Conditions of Water System

1) TI1 - Age of Pipelines

The water mains in Zaben were predominantly built between 1981 and 1984 using PVC pipes. Some pipeline sections were replaced since the initial construction and were either replaced with new PVC or with PE or high-density PE due to PVC defects. However, in relation to the total length of the network, the replaced segment is a very small component of the water supply system (approximately 8%). As such, the replaced segments did not have a significant impact on the evaluation of TI1. As the PVC water supply network in the municipality is predominantly 35 to 38 years old, TI1 was classified as K2

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(for ages 20 to 40), as per Table 3. Since the expected theoretical service life of the PVC pipe material is 60 years, the water mains are approximately in the middle of their service life and should not require replacement in the near future.

2) TI2 - Failure Rate

We investigated the frequency of system failures by year from 2005-2015. We also evaluated the trend in the frequency of failures and accidents on water mains over time and observed a small but steady increase in frequency. This trend line is also shown in Fig. 2.

Fig. 2: History of the number of failures and accidents in the water

supply system during the monitored period from 2005 to 2015.

In total, there were 42 failures and accidents in the water supply system of the village between 2005 and 2015. The total length of the waterline is 9.0286 km and the number of failures per kilometre of water line per year was 0.4229 pp/km/year. The most problematic section of the water system was the F line—which was categorised as K4 with 0.6413 pp/km/yr—whereas the failure rate was the lowest for line A—which was categorised as K1 with 0.2039 pp/km/yr. Thus, the most critical component of the drinking water supply system is Line F. Finally, Table 13 shows the categorisation of each line based on its individual failure rate while Table 14 shows a ranking of the lines by performance. Overall, the water supply system was categorised as K3 with regards to TI2. Tab. 2: Table 14 Order of water supply lines according to their failure

rates from worst to best.

Line Number of

failures/km/year

Number of failures/km/period

1 – Worst F 0.64 7.05

2 G 0.59 6.54

3 B 0.48 5.32

4 E 0.46 5.07

5 D 0.40 4.36

6 C 0.31 3.45

7 - Best A 0.20 2.24

3) TI3 – Water Losses

The volume of water losses, or the balance of WNI, was

obtained from the development plans of water supply and

sewage systems in the region (PRVKUK). These plans

state that ‘the proportion of water not invoiced is consistently higher, reaching up to 31% of the quantity of

water supplied to the system’ [4]. Due to these enormous

losses, the whole water system was categorised as K5 with

regards to TI3. This categorisation indicates water loss is

an emergency situation that requires immediate solutions.

4) TI4 – Pressure Ratios Pressure conditions in the water network in the village

were broadly comparable across the whole system because

the village lies on relatively flat plain where the altitude

differences are minimal. The water level in the reservoir

was between 306.5 and 311.8 m above sea level. The

maximum hydrostatic pressure in the water supply system

was thus 45.8 mH2O, while the minimum was 36.5 mH2O..

These pressure conditions in the village water network can

be considered as favourable, given Table 6. In particular,

45.8 mH2O is on the border between categories K1 and K2.

However, in normal operating mode the hydrostatic

pressure will be lower and thus the resulting category for

TI4 – pressure conditions of the water supply network—was K1.

5) TI5 – Water Quality Given that the village of Zaben is supplied with drinking

water from the regional water mains of Ostrava—which

contains predominantly surface water—the water in the

mains has adequate quality. Leakage may result in a

deterioration of the quality of drinking water in the

pipeline. Thus, the resulting category for TI5 was K3.

6) CTS – Overall Technical Condition

It was appropriate to determine the weight Wi as an

estimate, based on the significance of the indicators for the

CTS of the water supply network. Usually, the significance

of each TIi stems mainly from their classification. In this

case, we used equal weighting. Substituting Eq. resulted

in:

1

2 0,2 3 023 5 0,2 1 0,2 3 0,2 2,8=

= = + + + + =n

i i

i

CTS TU W

Table 3 provides a summary of the categorisation for each

TI and the overall condition (CTS). Based on the

evaluation, the entire water system was categorised as K3.

Tab. 3: Evaluation of the overall technical condition of water mains.

Technical indicators (TI) Relevant

category Wi TIi TS

TI1 – Age of the pipeline K2 0.2 2 0.4

TI2 – Failure rate K3 0.2 3 0.6

TI3 – Water losses in the

network K5 0.2 5 1

TI4 – Pressure ratios K1 0.2 1 0.2

TI5 – Water quality K3 0.2 3 0.6

CTS – Overall technical

condition K3 1 2.8

A categorisation of K3 indicates an average evaluation.

Considering this perspective, the overall condition of the

water network is likely unsatisfactory, especially due to

the enormously high water losses in the network. Thus,

urgent action is likely required.

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3.2. Funding and Planning for Water Main Renewal

Using Eq. we determined the percentage of wear as PO = 36.5 ∗ 10060 = 365060 = 60.8%

which is consistent with the fact the system is past

approximately half its service life. Subsequently, Eq. was

used to determine the TDAP by 𝑇𝐷𝐴𝑃 = 60 ∗ (100 − 60.8)100 = 60 ∗ 39.2100 = 2352100= 23.5 𝑦𝑒𝑎𝑟𝑠

Based on these calculations, the total theoretical time

required for accumulation of funds is 23.5 years, which

means that the water supply system should be

reconstructed in its entirety by 2042.

Given that the total value of the water mains in the village

is approximately 26.823 million CZK (€1.03 million), RPPO was calculated using Eq. (5) as 𝑅𝑃𝑃𝑂 = 26.823 𝑚𝑖𝑙𝑙𝑖𝑜𝑛 𝐶𝑍𝐾23.5= 1.052 𝑚𝑖𝑙𝑙𝑖𝑜𝑛 𝐶𝑍𝐾 ≅ €40,462 which is equivalent to CZK 10.52 million (€404,615) over the 10 years since the establishment of the legal obligation

to prepare a plan for financial renovation of water supply

systems. These funds should therefore be either invested

annually into water supply system renewal or the owner

and operator should plan extensive reconstruction on the

timescale of a few years, in which case the funds required

are proportionally increased.

Consider that the present annual water consumption is approximately 36,223 m3 /yr. and that WNI may account for up to 11,229 m3 /yr. Furthermore, consider that the price of water is CZK 34.40 (€ 1.32) / m3. As such, the financial loss is approximately CZK 386,278 (€ 14.856,85), which represents a significant annual financial loss to the operator of water supply network which may encourage operators to financially support and maintain the system [3].

4. Conclusion

This study has presented the water supply network of a model territory in the village of Zaben in the Czech Republic. We applied the methodology for evaluating the technical condition of the water supply system, according to the general FMEA approach. Based on this methodology, the evaluation of individual sections of the water mains was conducted according to their structural condition. We also proposed a financial and logistical plan for the reconstruction of the water supply system in the village on the basis of our analysis. Notably, the proposed time schedule was designed such that the sequence of individual water lines being renewed reflects their structural condition. The result is a schedule for water main reconstruction, where the priority is the renewal of those lines that are in the worst technical condition.

Acknowledgments

This work was supported by funds for the Conceptual Development of Science, Research and Innovation for 2020.

References

[1] CSN IEC 812 (010675). Methods of system reliability analysis. Failure Mode and Effects Analysis, (FMEA). Czech Republic, Prague: Czech Standards Institute, 2007.

[2] KUDA, František and Marek TEICHMANN. Maintenance of infrastructural constructions with use of modern technologies. Journal of Heating, Ventilation and Installation. Expert Journal of Environmental Technology Companies. Czech Republic, Prague: Society for Environmental Engineering, 2017, Vol. 26 (2017), Issue 1, Pages 18-21. ISSN 1210-1389. (in Czech)

[3] KUDA, Frantisek, WERNEROVA, Eva and Stanislav ENDEL. Information transfer between project stages in the life cycle of a building. Journal of Heating, Ventilation and Installation. Expert Journal of Environmental Technology Companies. Czech Republic, Prague: Society for Environmental Engineering, 2016, Vol. 25 (2016), Issue 3, Pages 156-159. ISSN 1210-1389. (in Czech)

[4] Development Plan for Water Supply and Sewerage Systems in the Moravian-Silesian region, Environmental Information System of the Moravian-Silesian Region. Czech Republic, Ostrava, 2014. (in Czech)

[5] TUHOVCAK, Ladislav. Methodology for assessing the technical condition of water mains. Czech Republic, Brno, 2010. Habilitation work. Brno University of Technology. (in Czech)

[6] Czech Republic. Decree No. 441/2013 Coll., implementing the Property Evaluation Act (Valuation Decree). In: Collection of Acts, 31 Dec. 2013.

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THE EFFECT OF ORIENTATION AND LOCATION OF BUILDINGS IN URBAN AREAS ON THE THERMAL STABILITY OF BUILDINGS

Michal FALTEJSEK1, Frantisek KUDA1

1 VŠB - Technical University of Ostrava, Faculty of Civil Engineering, Ostrava, Czech Republic


Abstract. Building and City Information Modelling provides a suitable basis for creating various simulations and analyses. Matters about new buildings, potential problems and crisis situations can be predicted using this method. Simulations can be used to verify the physical condition and behaviour of existing buildings. The location of a building in a city, the surrounding structures, its position, height or shape can affect the distribution of air currents through an area. Gusty winds and low air temperatures, especially in the winter months, can significantly cool down individual structures. This problem occurs mainly with older high-rise buildings not protected by surrounding buildings which are located, for example, at the edge of urban developments. They are directly exposed to gusty winds, and if their design is outdated and unsuitable, wind can greatly affect the surface temperatures of structures and transfer these temperatures to the indoor environment. This article discusses the effect of wind direction and speed and the effect of orientation and location of buildings on their internal thermal stability.

Keywords

Thermal stability, BIM, city information modelling, simulation.

1. Introduction

In this innovative age of digitalization, numerous simulations can be created for the construction industry. Building Information Modelling provides this possibility, but it is still not sufficiently widespread and applied in practice. Simulations can provide us with a lot of information that is often overlooked or seen as less important. They can help us determine future results before a structure is built or provide certain information for already existing buildings, such as the cooling of structures by wind and airflow.

Using the results obtained from simulations, construction costs can be reduced, and most importantly, the costs of future operations for planned constructions can be minimized. By applying simulations to existing buildings, reconstructions and upgrades can be planned effectively, critical spots can be determined, and potential problems can be predicted. The lifetime of specific structures, their properties and state of maintenance can aid in effectively determining the basic conditions for creating simulations. From the obtained results, the current conditions and problems can be analysed.

Detailed simulations are highly demanding on computing power and should be done using a supercomputer infrastructure. Greater detail in information and results and a finer and more detailed network of points describing the simulation increases its computational complexity.

This article focuses on simulating the wind flow around a building and its effect on the thermal comfort inside. This is also affected by the shape, height and dimensions of the building and, not surprisingly, by the construction solution, including the design of the external cladding.

2. Simulated Location Environment

Fig. 1: CIM - 3D model of the Ostrava-Poruba complex.

The location is on the outskirts of Ostrava–Poruba at an altitude of 250 meters above sea level. The individual buildings of the dormitory are considerably taller than the


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surrounding area and wind has no obstacles to alleviate its full force on the buildings. The wind can strike the buildings with a force of up to 40 km/h. The next chapter describes the extent of the wind’s impact on the thermal stability of the buildings.

3. Effect of the Orientation and Location of Buildings in Urban Areas

The orientation and location of buildings in areas of urban development has a great effect on the thermal stability of those buildings. Especially during winter and exposure to severe weather conditions from north and north-eastern winds, the internal and external temperatures of high-rise buildings can fluctuate strongly. The difference between the windward and the leeward side temperatures may be up to 4 °C. This difference affects the costs of heating the building considerably as well as the comfort of its residents/users and the lifetime of individual structures. The north-eastern wind was measured at 40 km/h with outdoor temperatures of around 4 °C. The peripheral buildings face gusty winds that then break up and slow down. Other buildings in the area are therefore not exposed to such a strong air current and the effect on these buildings is significantly lower.

Fig. 2: Simulation of cold air flow through the Ostrava-Poruba complex.

4. Conclusion

The results show that buildings on the outskirts of an urban area directly exposed to gusty winds and uninterrupted wind currents can significantly affect the thermal stability of the interior in the long term. This problem raises the cost of heating and maintaining structures. Other problems that may arise because of the building’s design in terms of poor orientation and shape are, for example, reduced lifetime of the structure, formation of mould and decreased user comfort inside the building. Especially in winter when the building is exposed to cold winds, non-insulated parts are strongly cooled down and the heat (cold) is transferred considerably through its structure. The simulated results of measurements conducted with a thermal camera verify the effect of wind on the building, and the measured values

demonstrate that the differences between the windward and leeward structures are significant on the exterior (surface of the structure) and especially in the interior. The differences inside the building are up to 4 °C.

The aim of this article was to examine the effect of orientation and location of individual buildings in urban areas on thermal stability inside those buildings. Simulations were used to describe wind currents, measured values and generally assess the conditions in an older high-rise building on the outskirts of an urban area. The results can help us highlight a general problem and solve thermal stability issues as well as emphasize the use of BIM models and creating simulations before construction of a building commences. Predicting potential problems and situations is an essential part of reducing additional costs.

Acknowledgements

The manuscript was supported from the funds of the Students Grant Competition of the VSB – Technical University of Ostrava. Project registration number is SP2020/160.

References

[1] FRÖHLICH, Dominik, Marcel GANGWISCH and Andreas MATZARAKIS. Effect of radiation and wind on thermal comfort in urban environments – Application of the RayMan and kyHelios model. Urban Climate. 2019, 27, 1-7. DOI: 10.1016/j.uclim.2018.10.006. ISSN 22120955.

[2] LAUSOVA, Lenka, SKOTNICOVA, Iveta. Analysis of experimental measurements and numerical simulations of a heat field in the light weight building structure. In: Advanced Materials Research, vol. 969, pp 33-38, 2014. DOI: 10.4028/www.scientific.net/AMR.969.33.

[3] LIU, Mingzhe a Per HEISELBERG. Energy flexibility of a nearly zero-energy building with weather predictive control on a convective building energy system and evaluated with different metrics. Applied Energy. 2019, 233-234, 764-775. DOI: 10.1016/j.apenergy.2018.10.070. ISSN 03062619.

[4] WEI, X., BONENBERG, W., ZHOU, M., WANG, J., WANG, X. The case study of BIM in urban planning and design. In: Advances in Intelligent Systems and Computing, vol. 600, pp 207-217, 2017. DOI: 10.1007/978-3-319-60450-3_20.

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POSSIBILITIES OF USE THE RAIL SIDING TRACKS AFTER FINISHING MINING ACTIVITIES

Miloslav ŘEZÁČ1, Leopold HUDEČEK1, Otto ROHÁČ1, Denisa CIHLÁŘOVÁ 1

1Department of Transport Constructions of The Faculty of Civil Engineering of Organization, VSB – Technical University of Ostrava, 17 listopadu 2172/15, Ostrava, Czech Republic


Abstract. Industrial Production has influenced the character of Moravia and Silesia since the turn of the 19th century when the Country started being industrialised. The dynamic development of the Ostrava agglomeration is thus inseparably connected with black coal mining, metallurgy and railway development. The development of mining in the past years was subject to a functional transport system, with prevailing requirements for the transportation of large volumes of extracted material, structural elements and people working in this industry. With the extraction downturn, the sources and objectives of transport have changed including the characteristics of transport flows of all traffic roads and connections. Fundamental changes in the structure of the industry reflect changes in public transport. In ours work we ares to examine as well the various ways of solving of these issues abroad, should there be any. For the use of rail sidings network in public transport, we defined main technical and economic parameters and subsequently we created a general methodology for the solution of "traffic brownfields". By the using of the methodology a model was created by which an optimal solutions and the definition of proposals of measures for achieving the vision of the use of the "traffic brownfields". Train-trams for Ostrava the could take up on the prior tradition of narrow gauge suburb railways in the Ostrava agglomeration.

Keywords

Brownfield, Decision-making, Investment, Mining impacts, Ostrava, Public Transport, Traffic, Tram - Train, Rail Siding Network.

1. Introduction to Problem

Industrial Production has influenced the character of Moravia and Silesia since the turn of the 19th century when the Country started being industrialised. The dynamic development of the Ostrava agglomeration is thus inseparably connected with black coal mining, metallurgy and railway development. The development of mining in the past years was subject to a functional transport system, with prevailing requirements for the transportation of large volumes of extracted material, structural elements and people working in this industry. With the extraction downturn, the sources and objectives of transport have changed including the characteristics of transport flows of all traffic roads and connections. Thus, in this area it is necessary to identify the consequences of mining, reclaim the landscape, reconstruct civil structures and ensure safe and reliable transport through transport-engineering measures which may ensure the required transport standard and minimise its adverse environmental impacts.

In ours work we ares to examine as well the various ways of solving of these issues abroad, should there be any.

In its analytical part, ours work deals with three essential issues:

• approaches to solving similar problems abroad

• the analysis of the public transport in Ostrava agglomeration

• the analysis of rail sidings networks in Ostrava agglomeration

In the development of transport infrastructure in Ostrava agglomeration, solutions and approaches from other





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industrial agglomerations have been taken over by, which is also true in the use of these industrial railway after the end of their primary function. The aim of ours work is to examine the various ways of solving some of these issues abroad, should there be any.

Fundamental changes in the structure of the industry reflect changes in public transport. Along with the considerations about the use of rail sidings network for public transport, we asked and analysed the following questions:

• What is the development effort in transport?

• What are the long-term trends in public passenger transport?

• What are the long-term trends in the division of transport work?

• Which directions does the main transport load lead to?

• How do the changes in the transport manifest and what are the implications of these changes?

The rail sidings network itself is defined territorially in relation to the previous requirements of the industry as well as the technical parameters in relation to the scale of the investment, repairs and also mining influences, which was and in some areas still is burdened with. For the use of rail sidings network in public transport, I defined some technical and economic parameters.

The information obtained from benchmarking and from the analysis of public transport has been used in:

• proposals and correctness verifications of the considerations relating to the future use

• verification of feasibility

• verification of economic indicators

• the selection of appropriate criteria for the assessment of the joined track sections

• the selection of appropriate merged track sections for the future purpose of the use in public transport.

As the processor of the dissertation, I initially asked myself the question why the hypothesis in the use of rail sidings network of public transport should be dealt with. There are a few reasons to it:

• the use of the multiplier effect of the transport infrastructure in the development of the territory

• extend the offer of public transport

• the prevention of the negative downward trend in public transport in favour of private transport

• the improvement of the environment

• the use of the rail sidings network transport potential for public transport

• to improve the mobility of the inhabitants in Ostrava agglomeration

• the avoidance of "brownfields"

• the use of the correction items intended for disposals on the further development of the territory.

It is obvious that these are social and economic reasons. In order to verify the hypothesis, we created a general methodology for the solution of "traffic brownfields". By the use of the methodology a model was created by which an optimal solution and the definition of proposals of measures for achieving the vision of the use of rail sidings network can be detected.

After certain modification of the criteria, this model can be further used in other "brownfields" solutions.

The effects of mining are a strongly negative factors for using industrial railways for public (suburban) transport. Tram, train, train-tram, bimodal tram, are names given to the transport system and vehicles enabling the transfer from train railways to tram railways, or a railway having mixed features (e.g. train railway in a municipality along the street). Train-trams for Ostrava could take up on the tradition of narrow gauge suburb railways in the area. We can consider mainly the Ostrava – Orlová track.

2. Benchmarking of public transport systems

TramTrain - a transport system that allows you to change from a railway line to a tram line. The advantage of the combined system is the more efficient use of tracks in sections where two tracks would otherwise run in parallel, and greater comfort for passengers. The most significant drawback of such a transport system is the transmission of irregularities from urban traffic to the rail network.

A high-speed tram, a high-speed track or a less light (city) railway (Light Rail in English speaking countries) is a form of tramway transport with a completely segregated track.

In the Czech Republic, one of the most up-to-date projects of this type was in 2003 the Regiotram Nisa Project and the Tram-Trains in the Ostrava region, which continue the Tradition of Narrow-gauge Suburban Railways in the Area and are intended to Address Traffic in the Ostrava agglomeration. Abroad, one of the Tram - Train transit systems is operated in Karlsruhe. Projects in other Cities, especially Germany, France, the Netherlands and England, are based on a similar Technical System.

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The High-speed tram is widespread in the United States of America under the name "Light Rail" especially in Los Angeles, Boston, Portland and San Diego. The High-speed Tram is operated eg in Manila, Philippines and in many Cities in Asia. In the UK, Railways (Manchester, Birmingham, Nottingham) are often used for High-speed Trams. In Slovakia, the high-speed tram operates in Košice.

The greater need for Mobility of the Population of the Agglomeration, the gradual disappearance of the purpose of using Industrial Railways and the approach to solving this Problem abroad, generates the thesis of exploiting the Potential of Industrial Railways.

A need can be included in the set of needs:

• increasing the efficiency of the use of the Rail Network

• increasing the Mobility of the Population

• improving the Environment

• prevention formation of Brownfields

• use of secondary Brownfields

• territorial development of the Ostrava agglomeration.

Prerequisites for using the Network include:

• technical Parameters

• more comfortable connection of settlement units and synergies in Transport.

To verify the Hypothesis about the Possible use of the Siding Network for Public Transport, the Problem analysis was carried out, a methodology for assessing the use of Traffic “Brownfields” was created and a Model that leads to conclusions confirming or refuting the suitability of the Rail Siding Networks for Suburban Transport.

In order to evaluate the utility of the Sidings Network for Suburban Transport, it is necessary to select Indicators, ie evaluation Criteria, which will be decisive for the change in the State and will play a decisive role in the usability of the suburban Transport Network. We assume that this Portfolio will include:

• technical Criteria, which would relate to the requirements specific to linear Structures,

• economic Criteria relating to the cost-effectiveness and efficiency of the Work,

• criteria related to the impact of mining activities, terrain reshaping and its impact on operations,

• criteria related to the remediation of Track Sections,

• environmental Criteria,

• transport Criteria.

3. Analysis and Models used for the Solution

The following Analyzes and selected Models suitable for hypothesis verification were applied for the solution:

Kepner-Tregoe Decision Analysis (K-T) Decision analysis K - T is a quantitative comparative method, in which the criteria and alternative solutions are evaluated numerically. The model is described in detail in [2], called Kepner - Tregoe Method.

Analytical Hierarchy Process (AHP) - Saaty model

The AHP method is a quantitative comparison method that allows the selection of a preferred alternative (variant) based on pairwise comparisons of alternatives (variants) and their relative convenience according to criteria. The model used is the AHP (Analytic Hierarchy Process - Saaty model), which is described in detail in [4], [5].

Analysis for - against

Analysis for - against is a qualitative comparison method; using which can determine for each variant its positive (for) and negative (against) aspects. The preferred option is the one with the strongest "for" and the weakest "against".

Project management

The project management method is used to verify the hypothesis of using industrial railway for public transport. Project management can be defined as a way of solving complex tasks with a high degree of uncertainty and complexity and a high incidence of unclearly defined problems, changes and risks.

Investment decisions

The investment decision-making process is linked to the acquisition and financing of fixed assets. Depending on whether or not the relevant methods of assessing the effectiveness of investment projects take account of the time factor, they can be divided into [6]:

• static methods - do not respect the time factor,

• dynamic methods - respect the time factor.

Strengths, Weaknesses, Opporttunities, Threats analysis

SWOT analysis is one of the basic methods of strategic analysis, precisely because of its integrating character of acquired, unified and evaluated knowledge, from which alternatives of further development strategies are generated.

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4. Figures

Fig. 1: Number of Passengers transported by Bus and Train in the Region between 2000 - 2010.

5. Conclusion

The work confirmed the hypothesis possible of using a part of the siding network for public transport. This, narrower selection of suitable track sections is a suitable basis for further work in the implementation phase and for further research into the involvement of the siding networks of the metallurgical and heavy machinery industries in the public transport system.

In the analytical part of the it was found that the Ostrava agglomeration is characterized by a high concentration of inhabitants with a decreasing trend. In the past, a high degree of economic activity was replaced, after social change, by the downturn and restructuring of heavy industry. The extinction of the purpose of using industrial railways abroad has generated the potential of using industrial railways in public transport.

The hallmark of this state in Transport is:

• increasing transport distance for job opportunities,

• long-term growth of individual car transport,

• long-term decline in public transport,

• deteriorating environmental status caused by increased emissions.

These factors, together with the decline of economic growth and prosperity of the agglomeration, are among the basic factors for the development of public transport as a multiplier of territorial development.

Acknowledgements

The works were supported from sources for conceptual development of research, development and innovations for 2020 at the VŠB-Technical University of Ostrava which were granted by the Ministry of Education, Youths and Sports of the Czech Republic.

References

[1] Q. JIA, N.Al ANSARI, S. KNUTSSON, S. DUST Generation Within the Vicinity of Malmberget Mine, Sweden, In: ADVANCES IN CIVIL ENGINEERING, PTS 1-4 Book Series: Applied Mechanics and Materials, Vol. 90-93, p. 752-759 DOI: 10.4028/www.scientific.net/AMM.90-93.752.

[2] KEPNER, C. H.; TREGOE, B. B.: The rational manager, New York: McGraw-Hill, New York 1981, ISBN-13: 978-0070341753.

[3] HUDEČEK L. and D. CIHLÁŘOVÁ. The Problems of Railways in the Undermined Areas. In: Conference proceedings 15th International Multidisciplinary Scientific GeoConference SGEM 2015. Bulgaria: June 18-24, 2015, Book1 Vol. 3, 713-718 pp. ISBN 978-619-7105-33-9 / ISSN 1314-2704.

[4] SAATY, T. L.: Theory and Applications of the Analytic Network Process, Pittsburgh, PA: RWS Publications, Pittsburgh 2005.

[5] SAATY, T. L.: The analytic hierarchy process - what it is and how it is used, Mathematical and Computer Modelling, Vol. 9 - 1987, Pages 161-176, ISSN: 0895-7177.

[6] KOUDELA, V.; SCHEJBALOVÁ, B. Ekonomická efektivnost investic, VŠB – Technická univerzita Ostrava, Ostrava 2000.

[7] KUTA V.: Rozvojové problémy Ostravské aglomerace, In: Mezinárodní konference a odborná výstava TRANSPORT 2001, Sdružení pro obnovu severní Moravy a Slezska, Ostrava 2001.

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THE IMPACT OF SOCIAL PERCEPTION ON THE CONDITION OF CEMETERIES

Klára PALÁNOVÁ 1, Ondřej JURAČKA1

1Department of Architecture, Faculty of Civil Engineering, VSB-Technical University of Ostrava, Ludvíka Podéště 1875/17, 708 00 Ostrava – Poruba, Czech Republic


Abstract. The Czech Secularized Society mainly uses cemeteries to remove ash which results in low attendance in municipal cemeteries. This lowers awareness of the necropolis and the dead and can cause problems with the tomb and potential vandalism. The aim of this research is to identify and analyze the needs and expectations of potential visitors to the cemetery in order to ensure future transformations of the necropolis and to increase interest in cemeteries. The research is based on a survey conducted in Ostrava, the third largest city in the Czech Republic. This was compared with an analysis of the current situation of cemetery equipment for visitors. The identified weaknesses will help steer the transformation of cemeteries so that they remain a full-fledged part of Central European cities. Article wishes to appeal to increase ceremony and respect for the last resting place of our predecessors by trying to reduce vandalism and improve care.

Keywords

Cemeteries, land use planning, cemetery renewal, vandalism, burial, grief.

1. Introduction

A general phenomenon evident in the condition of cemeteries, mostly of large cities, is the marginal interest of city representatives in the care and improvement of cemeteries, “despite the fact that it has direct impact on land use planning and social integration.” [4]. As a result of gradual secularisation, society is turning away from honouring the dead, which has a gradual negative impact on the direction, appearance and visiting rate of cemeteries [5][8]. The post-socialist society of the Czech Republic continues to face systematic support of departure from the church as promoted by the communist regime [6]. As a

result, the cemetery loses its privilege of consecrated ground, where the bereaved come to pray for their deceased loved ones. On the contrary, changes to the political regime in Czechoslovakia after 1948 resulted in a controlled transition from church ceremonies to civil ceremonies and systematic promotion of cremation [12]. Changes in the perception and use of cemeteries will also necessarily take place along with the spread of burials by cremation [7]. While death is the culmination of life and all its developmental phases for psychologists, for theologians it is the end of life on earth and the beginning of another life, while sociologists consider death the end of the path of life, p. 35 [13] and today’s society passes on its fear of death to the medical sciences and believes in their power. The desire to leave something of oneself behind is transferred from headstones and tombs in the direction of fame and earthly power [9].

Cemeteries used to be a truly public space in the sociological meaning of the word. They were accessible to everyone, open to the public. The bereaved visited them often and in great numbers, they took care of the graves and remembered their deceased. In the symbolic meaning of the words cemeteries are a place where the present and the past, the living and the dead meet. They used to be a place where people of various age groups, social classes, genders and races could meet and spend time together, p. 29 [10]. Today, in contrast to this fact, the Prague Cemeteries Administration has announced the “adopt a grave” event (www.hrbitovy-adopce.cz), where people can choose the grave of an important figure, towards the upkeep and care of which they will financially contribute, because these graves, specifically in cemeteries of the Capital City of Prague, lie forgotten, While cemeteries, which are part of the urban structure can serve at least as a place for taking a walk for mothers with prams or for relaxing during a lunch break, cemeteries in the peripheries remain nearly completely abandoned. It is the distressing condition of cemeteries in large cities that has encouraged us to consider the role of such complexes in today’s society and public space.



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The lack of interest in burial sites, poor maintenance or vandalism is mainly a problem in large cities. This does not apply as fully to smaller settlements. The loss of anonymity, the higher degree of religiousness, the smaller distances and consideration of public opinion assures more care of the place of rest of deceased love ones in smaller towns and villages [7]. The exception to this statement is abandoned original German cemeteries in the area of the Sudetenland after the German population was displaced after the Second World War. Some of them have remained completely abandoned, others continue to be used by the Czech population, however often with damage caused to the original headstones as a result of hatred. However, this is a separate topic, which we devote independent research to.

Fig. 1: The current locations of cemetery complexes in Ostrava.

2. Methods

We focused our research on cemeteries in Ostrava and our questionnaire was targeted at the three hundred thousand-strong population of Ostrava. The goal was to establish the frequency of visits to cemeteries, the reasons for these and the expectations of visitors with specification of weak points. Representatives of all ages and levels of education were addressed. The questionnaire survey took place at selected cemeteries in Ostrava themselves, but also outside them, in order to include people who never visit a cemetery or only infrequently. Research took place within the territory of the city of Ostrava during the month of July 2019 and included a total of 113 respondents. We included our assumed reasons for visiting the necropolis and also the negative aspects, which may influence the visiting rate to cemeteries from our viewpoint. We also gave the respondents an opportunity to give their own opinion. We were interested in how much our hypothesis would be confirmed or denied or whether we would encounter an opinion we had not heard before.

3. Results

We assumed more reasons to visit the cemetery than were subsequently shown to be relevant and we found this result very surprising. The reason is nearly always visiting a deceased love one, caring for the grave or the site of the urn/ashes and attendance of funeral ceremonies. Other reasons appeared in single cases and are therefore insignificant. This includes walking or meeting someone, artistic experience, etc.

In the event that the facilities lacking at the cemetery were specified, young people up to 45 years of age willingly confirmed our hypothesis of a lack of space for resting, prayer, meditation and space for refreshments, even just in the form of vending machines. Older people over 65 years of age, usually women, pointed out the feeling of danger and the ever-present vandalism.

With regard to the issue of vandalism and the visibly poor care of gravesites we were interested in the frequency of visits by respondents to cemeteries in Ostrava. The fast lifestyle, great distances and preference of life here and now, along with the generally low religiousness and also the anonymity of a large city generate a low visiting rate to cemetery complexes [7]. It is therefore positive that only 9 (i.e. 8%) of respondents admitted to zero visits to the cemetery (this mostly concerns people up to 45 years of age). A third admitted to visiting the cemetery only 1-2 times a year, mostly on the occasion of the state holiday of All Soul’s Day on 2nd November. This holy day is considered a social event and flowers are laid on the grave and candles are lit. The tradition has been supported by primary schools in recent years, which focus educational outings with pupils on cemeteries at this time. Another third of the respondents visits the cemetery 3 – 6 times a year, mostly at Christmas, Easter, the anniversary of the death or birth of the deceased or during a funeral. The reason for visiting the cemetery is usually a visit to a deceased loved one, to a lesser degree to care for the grave or urn site and to attend a funeral. Several individuals gave their reason for visiting a cemetery as walking, meeting someone or funeral tourism.

From the viewpoint of the sustainability of necropolises within the city organism it was also very important to establish the frequency of visits by individuals throughout the year. We found that 14 respondents (i.e. 12%) visit the cemetery once a month and 9 (8%) visit every week. However, this is conditional to the cemetery being a short distance away from their place of residence or employment (within 10 minutes).

What seems to be absolutely crucial for the future objective of cemeteries is the fact that nearly three quarters of respondents (69%) choose to visit at the weekend or on a state holiday, in the afternoon. The visiting rate is therefore significantly lower over the week, which is closely related to the respondents’ frequently mentioned (one fifth of respondents) need to increase safety (either using a camera system, patrols, municipal police and also by improving lighting away from the main cemetery

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routes) and also emphasis of the ever-present traces of vandalism and lack of interest in care of gravesites.

Fig. 2: Reasons for visiting cemeteries expressed as a percentage according to answers from respondents in the questionnaire survey (source: questionnaire survey).

On the basis of an analysis of current realisation of new cemetery complexes and the accompanying funeral architecture in Holland and Belgium, the questionnaire included an inquiry regarding restaurants or another options for refreshment within the cemetery complex. On the example of the Belgian realisation of a new cemetery with crematorium in Heimolen [2] with a restaurant situated close to the main entrance to the cemetery (but on the land of the necropolis) we can see an opportunity for this use by funeral guests for example and also by visitors to the cemetery. It is not usual in the Czech Republic to have any type of refreshments on the perimeters or within the cemetery complex, despite the fact that the location means half an hour travel for half of respondents and even 45 – 60 minutes travel for a quarter of respondents. The location of cemeteries at the periphery of the city assumes a longer journey. In the questionnaire 17 (16% respondents confirmed interest in any form of refreshments (even in the form of vending machines), mostly for the purpose of refreshment when visiting the cemetery, not for funeral banquets. Surprisingly this concerned people up to 45 years of age. This was closely linked to the requirement – by a third of respondents – to establish a sheltered area at cemeteries for rest or during poor weather.

This leads us to the comment by architect J. Almer [1], who writes of the need for an appropriate vacant space where vehicles and the public can gather in greater numbers. He considers the absence of such a space to be a defect particularly on the occasion of important funerals and various celebrations, particularly in the area surrounding funeral buildings and chapels, because neighbouring tombs and graves are often seriously damaged during similar large gatherings, particularly due to simple curiosity and often also the sensationalism of the crowd. The dimensions, modification and furnishings of rooms and buildings for displaying the deceased, organising funerals and funeral or posthumous ceremonies, are in most cases completely insufficient or even dismal in most cases at all cemeteries, unless funerals are held in churches

built especially for this purpose or at churches that are also parish churches. There is similarly no shelter for the public in the event of sudden poor weather, particularly rain. He also mentions the difficult access to some cemeteries by public transport and also access to graves, mainly in older parts of cemeteries, when the aspect of proceeds from lease of graves has exceeded the aspect of layout, where there are minimum paths and these are also unpaved, which means they turn muddy when it rains. p. 6 [1]. 2 respondents pointed out the layout and difficult access to densely situated graves.

Analysis of the results of the questionnaire survey confirmed that the abovementioned comments have not been dealt with over 90 years and remain of current interest, not only in Prague, but also in Ostrava.

Furthermore, in addition to ordinary shelters to protect against poor weather, 12 respondents added that they lack a space for meditation or prayer at cemeteries. The examined cemeteries in Ostrava usually lack a church chapel, in a minimum of cases they are equipped with a funeral hall and there is a crematorium at the central cemetery [11]. This concept is also supported by the fact that 26%, i.e. 313,847 residents of the Moravian Silesian Region (out of a total of 1,201,431 residents) [3], for whom Ostrava is a regional city, consider themselves religious according to the results of the 2011 census, whether they claim affiliation to a particular faith or not. This proportion increases the nationwide average and more attention devoted to this topic in the future would therefore be justified.

Fig. 3: Elements or services that are lacking at cemeteries or identification of the weak points of cemeteries as indicated by respondents (source: questionnaire survey).

If only a bench currently serves as such as place at the cemeteries in Ostrava (sometimes identified as a lacking or insufficient element of cemetery equipment in the questionnaire survey), this situation seems insufficient according to the current needs of society.

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4. Conclusion

Over the last one hundred years, since the time cremation was permitted in Czechoslovakia, there has been a marked change in burial methods, which historic cemeteries with skeleton graves have gradually responded to, albeit not very flexibly. However, attention should also be devoted to assuring suitable and expected facilities for the bereaved and other visitors to the cemetery. We focused on cemeteries in Ostrava, the third largest city in the Czech Republic, in order to prove the need for changes and the development of the needs and expectations of respondents living in the city, on the basis of a questionnaire survey.

This mainly concerns supplementation of existing complexes by minor architectural elements and landscape elements, the existence of which will provide a physical and also spiritual resource for visitors to the cemetery and the bereaved. We cannot expect Central European historic cemeteries to become a normal part of public space within the urban system. They will always remain isolated green gardens of peace, which however – particularly in large cities – will remain an important element of the city organism. It would be appropriate to compare our results with the opinions of respondents from other regions where we can assume significantly different rates of religiousness or with the distinctive function of funeral tourism, whereas different percentages of individual expectations and needs and also functions, where others would probably be added, in future research.

Acknowledgements

We would like to thank to Mgr. Kašpárková Alena, Ph.D. (Department of Environmental Engineering, Faculty of Mining and Geology, VŠB-TUO, CZ) for help with organization and advice on the publishing of the paper.

We would also like to thank to Mgr. Jitka Krčková, Ph.D. (Department of Mathematics, Faculty of Civil Engineering, VŠB-TUO, CZ) for help with questionnaire.

The work on this paper has been supported from the funds from the conceptual development of science, research and innovation for the year 2020 allocated to VŠB-TUO by the Ministry of Education, Youth and Sports Czech Republic.

References

[1] ALMER, J. About the need for reformation of Prague cemeteries. Prague: Pensions of the City of Prague, 1928.

[2] CLAUS EN KAAN ARCHITECTEN.

Crematorium Heimolen. A + U-Architecture and Urbanism, 2010. pp. 118-123, ISSN 03899160.

[3] Czech Statistical Office. 2019. Newest data: Moravian Silesian Region. [online]. In: https://www.czso.cz/.

[4] DAVIES, P. J. AND G. BENNETT. Planning, provision and perpetuity of deathscapes—Past and future trends and the impact for city planners. Land Use Policy, 2016. Volume 55, pp. 98-107, ISSN 0264-8377.

[5] K. H. Evensen, H. Nordh and M. Skaar. Everyday use of urban cemeteries: A Norwegian case study. Landscape and Urban Planning, 2017. Volume 159. pp. 76-84, ISSN 0169-2046.

[6] FIALA, P. and J. HANUŠ. The Catholic Church and totalitarianism in the Czech lands. Prague: Centre for the study of democracy and culture, 2001. pp. 216. ISBN 80-85959-98-4.

[7] FROLÍKOVÁ, K., M. PEŘINKOVÁ AND I. DLÁBIKOVÁ. Revitalisation of historic public cemeteries in central zones of Urban areas. WIT transactions on Ecology and the Environment. Volume 223, 2017, pages 147-158.

[8] FROLÍKOVÁ PALÁNOVÁ, K. and O. JURAČKA. Sustainability of existing areas of historic cemeteries in the city organism: A Czech case study. In: IOP Conference Series: Earth and Environmental Science. Volume 143. Bristol: IOP Publishing, 2018. s. 1-8. ISSN 1755-1307.

[9] FROMM, E. Mít, nebo být?. Second edition. Praha: Aurora, 2014. ISBN 978-80-7299-106-8.

[10] KOVÁŘ, J., M. PEŘINKOVÁ and N. ŠPATENKOVÁ. Cemeteries as public space. Praha: Gasset ve spolupráci s VŠB-TU Ostrava, 2014. ISBN 978-80-87079-44-7.

[11] LIPUS, R., L. POPELOVÁ and E. ŠPAČKOVÁ, ed. The world of architecture and theatre: architect Ivo Klimeš. Praha: Grada, 2014. ISBN 978-80-247-5268-6.

[12] ŠMOLÍK, J. Artistic and technical additions to columbaria and funeral halls. Society of the Friends of Cremation. Prague, 1968.

[13] ŠPATENKOVÁ, N. et al. The last things. Prague: Galén, 2014. pp. 19-20. ISBN 978-80-7492-138-4.

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POSSIBILITIES OF HOUSES VALUATION AUTOMATION

IN THE CZECH REPUBLIC

Stanislav ENDEL1, Marek TEICHMANN1, Dagmar KUTÁ1

1Department of Urban Engineering, Faculty of Civil Engineering, VSB-Technical University of Ostrava, Ludvíka Podéště 1875/17, 708 00 Ostrava – Poruba, Czech Republic


Abstract. There are currently two approaches to real estate valuation in the Czech Republic. The first is market valuation, i.e. determining the price at which real estate is realistically convertible on the open market. This valuation better reflects the real situation on the real estate market, but its partial disadvantage is the fact that the procedures used are only recommended and the valuation is thus influenced by the subjective opinions and feelings of the appraiser. Valuation is thus to some extent a science and an art. The second approach is the calculation of the so-called administrative (or official price), which is determined in accordance with the relevant legislation. The calculation procedure is fixed and the space for subjective considerations is minimal. However, it often happens that the administrative price differs from the market in the order of several tens of percent. The purpose of the article is to find and practically verify a method that would allow valuing houses, as one of the most frequently exchanged types of real estate on the Czech market quickly, relatively easily and in relatively large quantities, with the prices thus obtained very close to real market prices.

Keywords

Real estate valuation, floor area, price breakdown, automation in valuation.

1. Introduction

From the economics point of view, real estate is a very special commodity and the market is very specific and different from the markets with classic commercial products (e.g., prices are influenced by externalities, very limited supply at a given time, etc.). Thanks to this, the real estate valuation process itself is specific. Historically, there are many views on how the valuation should be performed, however, three approaches are currently the most

commonly used, namely cost, revenue and comparative valuation [1]. Ozdilek states that this is practically an approach based on a look at the past (comparison with other sales that have been realized in the past), a look at the present (setting current construction costs) and a look to the future (capitalization of future expected revenue) [12]. When determining market prices, the comparative approach is used most commonly [4]. However, with this approach, in some cases, the problem of lack of data may be encountered due to the low frequency of sales of similar objects [13].

There are a number of automated models for real estate valuation presented in the literature [2, 8]. Hedonic models are often used, which try to determine the parameters that affect the price of real estate and then assign a weight to the parameter, or examine the influence of one particular element on the price of real estate [6]. However, the authors agree that it is not possible to determine all the factors that affect the price of real estate. However, all models have one thing in common, and they agree that the location of the property is absolutely crucial to the price of the property.

It is logical that no two plots occupy the same place in space and the location of each is unique and unchanging. It is not possible to state that although the properties are completely identical in all other parameters, they also have the same price, because they will always differ at least in their location. Some systems try to take this fact into account, for example, by considering the price depending on the postal code [7] or the local segmentation of the real estate market [3].

However, no system is (and cannot be) perfect, because the final transaction price is always determined by agreement between the willing seller and the willing buyer. In addition, in this process, both parties are aware that they may influence the transaction price. Thus, it is never possible to determine the price of real estate exactly, some systems offer the range in which the price is most likely to move [13].



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Residential properties make up the vast majority of European cities. It is so logical that they are also most often exchanged. In the case of apartments, their valuation is relatively easy, which is also related to the possibility of relatively easy automation of valuation - there is no effect of land price and the market usually has a relatively large sample of similar properties that were sold in the past. With the knowledge of their floor area and the overall standard, it is thus possible to estimate relatively accurately the price per 1 square meter of an apartment of a given standard and in a given place, which can then be applied to the valuated apartment. It is necessary to take into account only the development of real estate prices over time [10].

In the case of houses, however, the situation is different and there are much more factors that affect the price of real estate - in addition to size, location and standard, also age, number of floors and their use, reconstruction, etc. Automation of valuation is much more complicated in this case.

2. Methodology

The methodology for possible future automated valuation is based on the following consideration. When assessing the costs of building houses in different locations, these costs differ significantly only in the item involving the acquisition of land, while the costs of the construction itself, while maintaining certain standards, are very similar. It is thus a question of whether this can be applied to older houses, i.e. whether it is possible to derive the market price of a house from the usual price of land in the place and further from the size of the house and the degree of wear.

Even with only a cursory inspection of real estate offers, it is clear that the prices of residential real estate are locally different, influenced mainly by the demand for housing in a given place. However, where the demand for housing is high, both land and houses already built are logically expensive, respectively the factors that influence the demand for the purchase of land intended for the construction of houses are the same as in the case of the factors that influence the demand for the purchase of finished houses in a given place.

If the total selling price of a particular house is known, it is not a problem to find out how large the land belongs to it from the publicly available data of the cadastral offices. Subsequently, it is possible to determine the usual price of such land on the basis of a comparison with other sales transactions of vacant undeveloped land that have taken place in the past, of course with an appropriate adjustment for price changes over time [10]. Thus, it is possible to abstract only the price of the house as such from the total selling price of a house and if its total net floor area is known, then also the price per square meter of this area. Clean floor area means the area bounded by the inner faces of plasters or other surface treatments of individual vertical structures, including non-load-bearing partitions [4].

3. Valuation procedure

The question is whether it is possible to determine the price of a house by composing the price of the land and the house as such, in other words, whether it is possible to apply the following equation to each family house with a sufficient degree of accuracy:

TP = LP + HP (1)

where:

TP – total price of the house including the land [€],

LP – land price [€],

HP – the price of the house itself [€].

As mentioned above, the price of the land can be determined separately by multiplying its acreage by the unit price normally achieved when selling similar land in the immediate vicinity. The price of the land is not unknown.

The price of the object as such is considered as the sum of the prices of the individual floors, with the price of each floor being given as the product of the net floor area and the determined unit price. However, it is clear that the unit price of each floor may be different on each floor – e.g. the unit price of the basement will certainly be lower than the unit price of the first floor - the cellar is not a standard living room, in most cases there is not enough natural daylight and there is a reduced ground clearance. For simplicity, consider the coefficient of use of the first floor above ground equal to 1, the coefficients for the other floors then represent unknown, as well as the unit price. If we consider the price of a basement family house with two floors, or one floor and an attic, the considered relationship can be mathematically written as follows:

HP = α1 × UPO × S1 + UPO × S2 + α3 × UPO × S3 (2)

where:

HP – the price of the house itself [€],

α1 – coefficient taking the use of the basement into account,

α3 – coefficient taking the possibilities of using the 2nd floor or attic into account,

UPO – unit price of the object [€ per square meter],

S1 – clean basement floor area [square meters],

S2 – clean first floor area [square meters],

S3 – clean second floor or attic area [square meters].

The product of the coefficients and the unit price of the object can be expressed as one unknown, i.e.:

α1 × UPO = β1 (3)

UPO = β2 (4)

α3 × UPO = β3 (5)

As mentioned above, the final price of a transaction in the

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sale of real estate is to some extent influenced by the subjective decisions of the participants, their ability to negotiate, etc. Price data are thus heteroskedactic and uncertainty must be taken into account. If we substitute equations (3), (4) and (5) into equation (2) and introduce the uncertainty Ɛ, we get the equation:

HP = β1 × S1 + β2 × S2 + β3 × S3 + ε (6)

The aim is to determine the values of the coefficients β1, β2 and β3 so as to create a generally applicable equation into which it would be sufficient to substitute the values of net floor areas of individual floors and thus determine the market price of a family house with a sufficient degree of accuracy.

However, there are still a few pitfalls in this equation. The first lies in the fact that the relationship does not take into account the standard of the object, respectively its wear. The calculation or estimation of house wear belongs to the standard tasks of the appraiser's work; therefore, it is not discussed in more detail here, in the conditions of the Czech Republic it is dealt with in detail by e.g. Bradáč [4]. Wear is given as a percentage, with zero wear corresponding to a new building, the higher wear means the lower standard of the building.

Another partial problem is the fact that real estate prices evolve over time. If the sale has taken place in the past, the change in time must be taken into account. In the Czech Republic, the development of real estate prices is monitored by the Czech Statistical Office [5] and the published data show that since 2016, both the price of building land and the price of houses have been rising. Since 2016, growth has been approximately linear, with the price of houses being about 0.6% higher each month. In the event of a different development of real estate prices over time, it is of course necessary to adjust the relevant value. The final form of the sought equation in the current situation thus looks as follows:

HP = (β1 × S1 + β2 × S2 + β3 × S3) × (1 - W) × (1 + MN × 0,60) + ε (7)

where:

W – wear specified in decimal degrees,

MN – the number of calendar months that have elapsed since the sale was realized.

As neither the wear and the time of sale are unknown, but can be determined before the calculation begins, this adjustment can be afforded.

4. Practical application

To demonstrate the possibilities of determining the values of these coefficients, a segment of houses was selected. The segment represents houses which can be basement and are single-storey with a residential attic - so they have a gabled roof and attic space is partially limited due to the slope of the roof planes. The size of the houses plots that

were included in the selection was limited to a maximum of 1,500 square meters - with a larger area, the unit price of the plot could be significantly affected by the achievement of economies of scale, which would distort the results. A total of 122 sales of houses in the city of Ostrava and its surroundings were analyzed. The data was selected from the database of properties actually sold - this database contains photos of individual properties, their brief description, as well as the development of the offered purchase price until the sale [11].

The actual sales prices in the Czech Republic since 2014 have been recorded by the Czech Surveying and Cadastre Office, which obtains the data directly from the purchase contracts submitted to it. This data is then publicly available, but for a fee. In the case of the examined sample of sales, the locally usual price of the land was deducted from the total purchase price achieved in each individual case, leaving the price for the object as such. Subsequently, the size of the built-up area of individual floors was measured in the cadastral map, which was multiplied by the standard coefficient of 0.75, thus obtaining the approximate net floor area of individual floors. Wear and a coefficient taking into account the change in price over time were also determined for each object - see above.

From the obtained data, the values of the sought coefficients were obtained by standard multiple regression using the least squares method. These values are as follows:

β1 = 336,59

β2 = 35 500,09

β3 = 19 847,12

Substituting the values of the coefficients into equations (3), (4) and (5), we obtain the coefficients α1 and α3:

α1 = 0,009

α3 = 0,559

The basic descriptive outputs of the performed multiple regression analysis are given in the Tab. 1:

Tab. 1 – Basic descriptive outputs of the performed regression analysis.

Correlation coefficient R

0,992268

Correlation determinants R2

0,984596

Coefficients

Mean value error

t ratio P ratio

Basement floor area

336,6 1309,2 0,26 0,80

First floor area 35500,1 1258,9 28,20 1,61*

10-54

Attic area 19847,1 1583,0 12,54 1,68*

10-23

The correlation coefficient and correlation determinations show a very strong dependence between the floor areas of buildings and their total price - but this is quite clear and expected. A relatively surprising finding, however, is the fact that the floor area of the cellar affects the total price of

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the house very minimally. The fact whether the object is a basement or not is completely irrelevant to the buyer.

The results also show a lower effect of the attic floor area. In other words, if two houses with the same floor area are sold, one of which will be one-storey and the other one-storey with a residential attic, the one-storey house will be sold at a higher price. This is due to the fact that only houses with gabled roofs were selected for the analysis, where the use of attic space is limited by the slope of the roof planes, and to the general reluctance of people to walk up the stairs [9].

5. Conclusion

In this way, the valuation of houses can be automated. However, it is always necessary to perform the analysis only for a certain segment of family houses. After performing a regression analysis, it is possible to obtain the values of coefficients needed for the calculation, which can be entered into the system and the user then only when determining the market price of a particular family house will provide data that can be determined from public sources, or they can be specified by the owner of the assessed property - the area of the land, the usual price of the land on the site, the floor area of each floor and the estimated rate of wear. With the exception of a few cases, the deviation of the above calculation from the actual market price of the property is up to 20%, in about 80% of cases up to 10%. The price can thus be calculated relatively accurately. This method is also very little dependent on the subjective opinion of the processor. If it is possible to determine the β coefficients for other segments of houses, or for other types of real estate, it is possible to create a system that will make it possible to determine the market prices of family houses with very small deviations. This system can then be used, for example, for tax purposes.

However, this method can also be seen as a way to find the usual price of land in a given place where data on actual sales of land in a given place are not available, but where houses are sold - typically in densely populated areas with a lack of vacancies. land.

Further research in this area should be focused on finding the values of the relevant coefficients for other segments of houses, or it is possible to verify whether the method may be functional for other types of buildings (e.g. commercial units, production halls, etc.). It would also be beneficial to make the method of calculating wear more objective, especially for older objects.

References

[1] ARRIBAS, I., F. GARCIA and F. OLIVER. Mass appraisal of residential real estate using multi-level modelling. International Journal of Strategic Property Management. 2016, vol. 20, iss. 1, pp 77-

87. ISSN 1648-715X.

[2] BARAŇSKA, A. Real Estate Mass Appraisal in Selected Countries – Functioning Systems and Proposed Solutions. Real Estate Management and Valuation. 2013, vol. 21, iss. 3, pp 35-42. ISSN 2300-5289, DOI: 10.2478/remav-2013-0024.

[3] BOURASSA, S. C, M. HOESLI and V. S. PENG. Do housing submarkets really matter? Journal of Housing Economics. 2003, vol. 12, iss. 2, pp 12-28, ISSN 1096-0791, DOI: 10.1016/s1051-1377(03) 00003- 2.

[4] BRADÁČ, A. Teorie a praxe oceňování nemovitých věcí (Theory and practice of real estate valuation). Brno: Akademické nakladatelství CERM, s.r.o. Brno. 2016. ISBN 978-80-7204-930-1.

[5] Český statistický úřad ČSÚ. Český statistický úřad | ČSÚ (Czech Statistical Office) [online]. Available in: https://www.czso.cz/.

[6] DU, M. and X. ZHANG. Urban greening: A new paradox of economic or social sustainability? Land Use Policy. 2020, vol. 92, ISSN 0264-8377, DOI: 10.1016/j.landusepol.2020.104487.

[7] FIK, T. J., D. C. LING and G. F. MULLIGAN. Modeling spatial variation in housing prices: A variable interaction approach. Real Estate Economics. 2003, vol. 31, iss. 4, pp 623-646. ISSN 1540-6229.

[8] FÜSS, R. and J. A. KOLLER. The role of spatial and temporal structure for residential rent predictions. International Journal of Forecasting. 2016, vol. 32, iss. 4, pp 1352-1368. ISSN 0169-2070.

[9] GEHL, J. Cities for people. 2012. Washington DC: Island Press; First Edition. 159726573X.

[10] HIMMELBERG, C., C. MAYER and T. SINAI. Assessing high house prices: Bubbles, fundamentals and misperceptions. Journal of Economic Perspectives. 2005, vol. 19, iss. 4, pp 67-92. ISSN 1944-7965, DOI: 10.1257/089533005775196769.

[11] INEM – komplexní informační servis (comprehensive information service) [online]. Available in: http://www.inem.cz.

[12] OZDILEK, Ü. On Price, cost, and value. Appraisal journal. 2010. vol. 78, iss. 1, pp 71-79. ISSN 0003-7087.

[13] RENIGIER-BIŁOZOR, M., A. JANOWSKI and M. D’AMATO. Automated valuation model based on fuzzy and rough set theory for real estate market with insufficient source data. Land Use Policy. 2019, vol 87, ISSN 0264-8377, DOI: 10.1016/j.landusepol. 2019.104021.

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METROPOLITAN SUSTAINABILITY AND TRANSIT ORIENTED DEVELOPMENT OF TOKYO

Tomoya KAJI1

1Department of Political Science, Faculty of Law, Meiji Gakuin University

1-2-37 Shirokanedai, Minato, Tokyo, Japan

[email protected]

Abstract. The population of cities had been growing over 40 years since 1960s and reached 128 million at the peak in 2008 in Japan. From this point Japan has entered a period of pronounced population decline. By 2035, the population of Japan is projected to drop to under 100 million. It would expect to 49 million in 2100 without dynamic demographic transition. According to a recent research, in the 896 (out of 1,741) local governments’ jurisdiction area, the female population from 20 through 39 years old estimates to decrease toward a half of it. Reflective of this general downward population trend is the rapidly increasing number of shrinking cities. For example, from 1990 to 2007, 26.7 percent, or 70 of the 262 municipalities with population over 100,000, lost population. Further, along with lines, from 2006 to 2007, the percentage of these municipalities losing population rose to 45.8 percent and today nearly half of them are shrinking. Moreover, among municipalities with population under one hundred thousand, percentage of shrinking cities is considerably higher. This means that population at the half of local governments’ jurisdiction might almost disappear until 2040.

In Japan, the ratio of urbanization promotion area of the whole land is just 3.8 %; however, 67.1% of the total population are living in this 3.8% land area. Furthermore, 93% of the total population in Japan live in

the urban planning area where only one fourth of the

whole land is designated. For more than 40 years, outskirts or the hinterland had been merged into urbanized. Now some of urbanized area has begun to shift into pseudo-suburbanized area in sprawling land use. Many countries in Asia have been recognizing suburbanization in the growing stage. On the other hand, reversely, Japan starts tackling suburbanization in the declining stage. The major factor behind this dramatic population loss is declining birth rates. In addition, given Japan’s strict regulation of overseas immigration, population decline will surely continue into the foreseeable future.

The railway system has taken significant role for economic development, modernization and urbanization of Japan. Historically, railways had been being developed much faster than road development even after motorization stage. National budget and human resources had been concentrated into building up national network of railways. In particular, high-speed express train services, so called bullet trains, have made efficient personal and physical distribution and contribution since 1960. However, this national network has promoted economic centralization into Tokyo because every local personnel and products have been closely connected with Tokyo. At the same time, rapid suburbanization and urban sprawling has taken places in the metropolitan areas. For instance, the railway network in Tokyo metropolitan area is composed of a regional separation system in lack of competition. Historically, private railway companies have not provided services within the built-in area of Tokyo. Metro services run by the government have been provided within the built-up area. The roles of private rails and public ones are divided geographically in the metropolitan area. Regional railways are connected with metro subways by passing through train services without change of trains at stations even in the different operators. In suburbs, private railway companies provide bus services and run taxi along with the railways, which is called joint-node transit system because regional rail stations take role of the joint of whole transit stream in the region. One third of the Japanese population are living in the Tokyo metropolitan area. The key feature of metropolitan transit in Tokyo is the private railway companies acted as regional developers as well as transportation providers, that is known as Transit Oriented Development. The merits and demerits of the development seem to balance out.

Surprisingly more than 70 percent of consolidated net sales of private railway companies in Japan are derived from non-transportation businesses such as housing development, entertainment and commercials. Four


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important factors can be observed as the reasons why the private railway companies have been heavily depended upon non-transportation businesses as regional developers. The first one, the primary housing programs of Japan has been based upon house ownership policy even within cities rather than apartment rent control. The younger generation have a dream to own a house with a garden even though it is very tiny one once they have started to work. The metropolitan regions have expanded and been sprawling since they have sought affordable houses in the suburbs and the outskirts, which national and local governments have supported to on their economic and financial programs. The second, land use of urban planning has promoted suburbanization and sprawl. The floor-ratio in the built-in area has regulated in the lower level and restriction of rural development has been lax. The third, railway network construction has an essential role in the national transportation policy. The road conditions are poor even in big cities because the roads have come to the end of their service life. For example, the road ratio of Tokyo is only 8.6 percent in spite of 23.2 in New York, 20.0 in Paris and 16.6 in London. The fourth, taxation policy has encouraged longer commuting in the metropolitan regions. In Japan, all the companies provide the workers with commuting allowance. Furthermore, this allowance deals with tax exempted income for workers and tax deduction expense for companies. Commuting from the outer-rings usually brings lower housing cost but higher economical cost of transit for workers. However, they endure physical cost of longer commuting thanks to this taxation policy only.

The population of the suburbs and the outskirts of the metropolitan region had been growing due to the above mentioned factors and regional railway operation. However, the population at the outer-rings of the region has declined because of shrinkage in cities and regions in aging society. The transit oriented development and its maintenance are facing their turning points.

Keywords

Joint-Node Transit System, Passing Through Train Service, Transit Oriented Development, Tokyo Rail Transit, Urban Sprawl.

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URBAN TRAFFIC EMISSION AND POTENTIAL BEHAVIOURAL-TECHNOLOGICAL SOLUTION

Tu Anh TRINH1, Linh Phuong Thi LE2

1 Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam 2 Faculty of Airport, Vietnam Aviation Academy, Ho Chi Minh City, Vietnam


Abstract. Road transport in Ho Chi Minh City have contributed a substantial emission of air pollutants that have damaged the environment and public health. It is important to determine the emission sources and the amount of emissions generated. The aim of the paper was to estimate the emission inventory from road transport in HCMC using EMISENS. The paper conducted a survey of traffic and vehicle characteristics using video camera, questionnaires. The data were gathered for 3 typical road types in 3 zones, for five typical vehicles. Other information (temperature, vehicle speed, emission factor) was also collected. The analysis revealed that vehicle feet released large amounts of CH4, CO, NOX, SO2, MNVOC (ktonnes yr -1). Motorcycle was the major source of CO, NMVOC, SO2 emission while car contributed the highest share of NOx. The promising behavioural-technological solution in terms of model shift, alternative fuel usage, the application of ITS were also introduced.

Keywords

Emission, EMISENS, ITS.

1. Introduction

Traffic emission has become a significant contributor of air pollution in many Asian developing cities. Along with the socioeconomic development and a rapid growth in vehicle fleet leading to high traffic density and congestion problem, Vietnam is known as one of the most polluted countries in the world. Concerns have been growing about air pollution associated health impacts in some polluted cities, such as Ho Chi Minh City (HCMC) where motor vehicle is the main mode and have been used extensively. In the city, there was about 7,4 million motorcycles registered in 2016, which accounted for 80% of the total fleet. The rest is composed of cars, buses and trucks. Most researches verify that the city is experiencing some of the

worst air pollution in the world and although urban pollution originates from a wide range of sources, the majority comes from transport emissions Moreover, the vehicle fleet consists of a variety of year models and technologies. The shortage of regulation and adequate emission inspection facilitates the use of old and dirty vehicles. Recent studies point out that air pollution generated by traffic have become a serious impediment to the quality of life and urban health. A range of gaseous pollutants such as volatile organic compounds (VOC), nitrogen oxide (NOx), carbon monoxide (CO), sulfur oxide (SOx) and methane (CH4) is released from the vehicle fleet. These emissions increases the risk of neurodegenerative diseases (Lee et al. 2016) and contributes to tropospheric ozone concentrations and secondary organic aerosols, which results in respiratory and cardiovascular system effects (Laurent and Hauschild 2014). Moreover, sensitive groups such as children and the elderly are at risk to urban air pollution. Apart from the detrimental health effects, studies suggested that the average economic loss per person per day caused by air pollution could approach as much as 729 VND. This economic loss is considerable in terms of direct medical costs (i.e. hospital admissions and the cost of pharmaceuticals) and indirect medical costs (i.e. time lost from work and premature death). It is urgent to have a well-designed strategy for emission reduction.

In Vietnam, road transport contributes significantly to air pollution and jeopardizes public health in the cities but has not been adequately characterized. Also, the available data are also insufficient to identify the contributions from motorcycle as well as other types of vehicle to the air pollution in the city. To make improvements in the air quality and having better urban air quality management, information on traffic-related air pollutants that are based on an accurate emission inventory is required. To this end, the objectives of the study were to (1) characterize the emission inventory from road traffic sources in HCMC and (2) propose the promising solutions for emission reduction. In fact, more updated information



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on emission inventory plays an important role because it is the foundation of control programs for selected pollutants (Shuhaili et al. 2013). A great majority of solutions for emission reduction in transport in terms of social change have been documented (e.g. active transport, model shift); however, given the potential for technology enabled green transport specially fuel consumption savings and emission reduction, environmental impacts of Intelligent Transport System will also be described in the study. In the study, Section 2 and Section 3 presents Methodology to investigate urban traffic emission and the findings. Section 4 describes the potential behavioural-technological solution for emission reduction.

2. Methodology

2.1 Traffic Emission Inventory

Given the growing environmental and health concerns, a substantial body of literature has been produced on emission inventory. To support agency regulatory objectives, an emission inventory which is an accounting of the amount of pollutants discharged into the atmosphere have been developed over the past several years. A comprehensive emission inventory is the first step to develop an emission control strategy for selected pollutants (Gulia et al. 2015). Along with the aforementioned studies of health impact, much of the work on vehicle emissions in the past decade has tended to focus on emission inventory in several urban agglomerations. Also, emission inventory models are available allowing users to vary the fleet structure, technology proportions, vehicle activity and proportions of driving conditions to estimate emissions and total fuel consumption (Boulter and McCrae 2007).

US EPA has developed a range of different emission models including MOVES, MOBILE-6 and NMIM. Kota et al. (2014) conducted a research on emission inventory of CO and NOX from on-road vehicles using MOBILE 6.2 and MOVES in Southeast Texas, USA. The study found that MOBILE 6.2 provides quite accurate estimates of emissions from the mobile sources when compared to MOVES. COPERT has been commonly used in EU in support of emission load estimation from motorized vehicles (Ekström et al. 2004). In China, Zhou et al. (2010) relied on MOBILE5B-China based on US. EPA’s MOBILE5B and PART5 for motor vehicle emission inventory estimation.

A review of the literature has shown that limited studies have been done to develop emission load models for heterogeneous traffic conditions in developing countries. Ho and Clappier (2011) pointed out that existing models required a lot of input parameters that were only specific to certain types of fuel, vehicle technology, road configuration; and developing countries with different conditions was not likely to use the models. In addition, the rapid economic development and the composition of traffic in developing countries that is mixed with a variety of vehicles, motorized and non-motorized accentuate the

need for developing approaches to collecting and reporting emission inventory data so that it is a reliable and credible source of information facilitating sound decision making. Based on the above-mentioned reasons, Ho and Clappier (2011) developed EMISENS model - a new approach for generating road traffic emissions to contribute to a better management of the urban air quality in developing countries. EMISENS model combines the top-down and bottom-up approach and using Copert IV methodology to generate vehicle emission inventories in developing countries with low quality traffic data. The model also computes the uncertainties due to input parameters in using Monte Carlo method. According to COPERT IV methodology, the model considers three emission types: Hot emission (Ehot) – emissions occurring under thermally stabilized engine and exhaust after treatment conditions (Ong et al. 2011), Cold emission (Ecold) - emission generated when vehicles are driven with cold engine and Evaporative emission (Eevap) - emission estimated for NMVOCs emissions and for gasoline passenger cars, gasoline light trucks and motorcycles (Ho and Clappier 2011). Total emissions are calculated based on equation:

E = Ehot + Ecold + Eevap (1)

where,

Ehot : hot emission,

Ecold : cold emission,

Eevap : evaporative emission.

The input and output data of the model presents in Fig. 1. EMISENS has been applied in the cities of both developed and developing countries, e.g. Ho Chi Minh (Vietnam), Strasbourg (France), Seoul (Korea), Bogota (Colombia), and Bangalore (India) with promising results (Ho et al. 2011).

2.2 Study Areas and Data Collection

2.2.1 Study areas

The availability of reliable local data plays an important role in calculating emission inventory (Nesamani 2010). Data are not readily available in HCMC; therefore, it will be important for surveys to calculate emission inventory. Given time and financial constraints, it is infeasible to collect vehicle data in all areas, so the survey was only carried out in selected streets. EMISENS estimates vehicle emissions by using street categories and vehicle groups (Ho and Clappier, 2011). Regarding street categories, the streets were grouped into 5 categories based on the speed and function of the street (i) urban main street; (ii) urban secondary street; (iii) urban street in industrial zone; (iv) rural street and (v) highway street category. Via mobile devices, we manually collected traffic counts in (i) urban main street, (ii) urban secondary street and (iii) rural street, which represents central district, urban district, and suburb

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respectively. Central district includes the busiest and most heavily congested roads, and more expensive motorcycles were observed in this zone while urban district have mainly narrow and busy streets. The majority of old motorcycles and light truck were observed there. Narrow streets dominate suburb, mostly old motorcycles and truck were observed in the area (Fig. 2).

2.2.2 Data collection

Traffic characteristics: In terms of vehicle category, the vehicles were classified into 5 categories, namely, car (all the passenger car and private car), light truck (≤ 2.5 ton), bus (urban bus and coach) and motorcycle (2 strokes and 4 strokes) (Ho and Clappier, 2011). Traffic count provides street-level traffic data for each street. The manual traffic count was recorded in 15-minute intervals on weekdays (Monday-Friday) and weekend (Sunday) during AM (from 7:00 to 9:00) and PM (from 16:00 to 18:00). For vehicle speed measurement, we used our motorcycle to follow vehicles running on the road and then found out the speed based on our motorcycle’s odometer.

Emission factors: In the study, we use emission factors (EFs) suggested by (Ho and Clappier, 2011). The authors stated that they employed the EFs from the three different sources. Given the lack of EFs of SO2 and CH4, EF of SO2 from China was used and EF of CH4 was derived from Copert IV. The EFs calculated for HCMC (Belalcazar et al. 2009; Dung and Thang 2008).

Vehicle characteristics: A set of attributes including vehicle age, vehicle category, fuel type, mileage of vehicle, and number of trips per day was collected by online survey. The survey was conducted from 15/9/2016 to 30/9/2016. The data is drawn from an online survey of motorcyclist. Car, motorcycle, light truck, heavy truck and bus/coach were considered in the survey. Besides, information on the number of registered vehicle in 2015, temperature and street length were also gathered.

3. Result and discussion

3.1 Traffic Volume and Vehicle Fleet Characteristic

Tab.1 presents the hourly traffic volume of five vehicle categories for the weekday (Monday – Friday) and during AM (from 7:00 to 9:00) and PM (from 16:00 to 18:00). A summary of their hourly traffic volume for the weekend is given in Appendices. The total traffic flow in central district was higher than those in urban district and suburb, reaching above 18,000 vehicles h-1 and 21,000 vehicles h-1 at off-peak time and peak-time respectively (Fig. 3). There is no data available for light truck and heavy truck in central district and urban district, which reflects the fact that light truck is not allowed to enter the areas from

6:00AM to 8:00AM, and heavy truck is not allowed to enter from 6:00AM to 21:00PM.

Fig. 1: The hourly traffic volume in the three kinds of street, vehicle h-1.

Higher traffic volume was recorded during weekday (i.e. 14,000 – 21,000 vehicles h-1) and lower was recorded at weekend (i.e. 9,000 – 16,000 vehicles h-1) in three streets. During the period of 7:00–8:00AM and 17:00– 18:00PM and during weekdays in central and urban districts, more traffic congestions were observed, whereas there were no noticeable rush hours and traffic jams in suburbs.

Apart from traffic volume, feet compositions also play an important role because it impacts on the emission inventory generated by different types of vehicle. In urban main street and urban secondary street, motorcycle was the most predominant vehicle type that had the largest share (>90%) of the fleet on weekdays and weekend. While car accounted for ~5%, bus was of the smallest share, below 1% (Tab.1). The fleet in suburb was dominated by motorcycle (47-66%), heavy truck (28-48%), car (1-3%), and light truck (1-2%) while bus only contributes a share of ~1%. Fig.4 shows the variation of the fleet composition (in %) at Road No.7 (Cu Chi Suburb). To investigate the vehicle fleet characteristic, a survey was conducted from 15/9/2016 to 30/9/2016 at residential areas, open markets, parkings, bus stations in central district, urban district and suburbs. A questionnaire was developed to interview vehicle drivers in HCMC. In total, 10 participants were involved in the interview (49 motorcycle riders (40,8%), 19 car drivers (15,8%), 12 bus drivers (10%), 27 light truck drivers (22,5%), and 13 heavy truck drivers (10,9%)). Characteristics, i.e. vehicle age, fuel type, engine type, mileage of vehicle were identified.

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Fig. 2: The fleet composition (in %) at Road No.7 (Cu Chi Suburb).

The results show that 98% of the motorcycles was equipped with four-stroke engine. The average age was 3 years. More than 60% were of below 3 years old and the remains were produced less than 6. Although the majority has been manufactured in recent years, motorcycle has become a main source of pollution. The survey also revealed that 52% of motorcycles are vehicles non-compliant with EURO standards. Only 33% complied with EURO II and 15% with EURO III. Motorcycles (99%) and cars (70%) used gasoline while the main fuel used by heavy truck and light truck was diesel (72%). The majority of bus used dual fuel (diesel and CNG). More than 90% of the cars follow the EURO III and EURO IV. Most of the light trucks, buses, heavy trucks, which is of Vietnamese and Korean made with the model years ranged between 1994 – 1996 and 2000 – 2005, had no engine standards or complied with Euro I or Euro II. The total mileage of motorcycle and car was low, reaching below 20,000 km and 50,000 km respectively. Heavy trucks, light trucks and buses with odometer readings ranging from 100,000 – 300,000 km accounted for more than 50%.

3.2 Emission Inventory

The results of traffic-related emission inventory for the year 2016 calculated by EMISSEN are given in Tab. 2. The analysis revealed that vehicle feet in HCMC released 14.91 ktonnes of CH4, 1763.71 ktonnes of CO, 547.52 ktonnes of NOX, 4.19 ktonnes of SO2, and 193.62 ktonnes of NMVOC. Motorcycle and car were the main contribution of CH4 which occupied 55.20% and 33.80% of the total emissions respectively (Fig. 5). Motorcycle was the major source of CO and SO2 emission with a record 54.37% and 50.36% of the total CO and SO2 respectively. Car contributed the highest share of NOx, above 34%, followed by heavy truck, above 22%, light truck (18.48%) and motorcycle (17.96%). Motorcycle generated around 101 ktonnes of NMVOC and was the main cause of NMVOC (52.18%). Overall, CH4, CO, NMVOC and SO2 produced by motorcycles were more than 50% of total road transport emissions. This was in line with previous finding that motorcycle was the major cause of pollution in HCMC (Ho and Clappier, 2011).

In 2011, motorcycle was around 86% of the total vehicles in HCMC and a large number of motorcycles had low quality engine with low proper maintenance. (Ho et

al., 2011). In 2016, motorcycle still remained the largest share (>90%) of total vehicle fleet. From 2011 to 2016, the number of motorcycle in the city increased at a rate of 8.1% per year, reaching over 7.4 million in 2016. Besides, there was an increase in the number of car, from 493,000 in 2011 to 556,000 in 2015. This rapid growing of motorcycle and car contributes significantly to air pollution in the city. The results of emission inventory can be used as a foundation for designing emission control strategy facilitating emission reduction in HCMC. Three potential strategies will be given and discussion in the next section.

Fig. 3: The distribution of road transport emissions.

4. Potential Behavioural-Technological

Solution

4.1 Behavioural Solution

Motorcycle and car have becoming the major cause of pollution in HCMC. Therefore, the strategies only focused on motorcycle and car. Three potential emission strategies were developed based on the assumption that 10% of motorcycles shift to public transport (Case 1), 10% of car shift to public transport (Case 2) and 10% of car shift to vehicles using biofuels (Case 3) while retaining the same other input parameters (i.e. speed, street category, emission factors). The results are given in Tab. 3. Compared to the base case, emission reduction strategies for different pollutants ranged from 2.63% to 14.39% (Case 1), 1% - 20.12% (Case 2), and 8.20% - 19.7% (Case 3). It is clear that the decline in the number of motorcycle and car can significantly mitigate road transport emission in HCMC (Tab. 3).

The majority of motorcycle in HCMC is equipped with 2-stroke engine, which is less fuel-efficient than other types of engines and produces high pollution levels. Therefore, reducing the number of motorcycle can mitigate exhaust emission. In the Case 1, it is clear that there was a significant reduction of CH4 (14.15%) and NOX (14.39%) compared with the base year while SO2 emission was reduced in the small amount (4.08 ktonnes). With regard to CO, the figure dropped from around 1763 ktonnes in the base reference to around 1688 ktonnes in 2010. Similarly, the amount of NMVOC fell by approximately 8 ktonnes by shifting 10% of motorcycles to public transport. Looking at the Case 2, NMVOC is

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SO2

NOX

CO

CH4

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generated by gasoline vehicles; therefore 10% shift of cars led to a significant reduction of CH4 (20.12%) and NMVOC (10.41%). The total CO and SO2 emissions decreased to 2.82% and 2.39% respectively from the base year, but there is no significant change in NOX emissions. Because light truck and heavy truck contributed a relatively large amount of NOX (Tab. 3), the shift of cars did not have considerable impact on NOX emission. Public transport occupies less road space and causes less pollution per passenger-km than other modes (Ong, Mahlia and Masjuki 2011). It is also regarded as a key target for reducing road transport related emissions (Gregory et al. 2016). HCMC is now characterized by a very limited supply of public transport services and a very low reliance on public transport for mobility. In fact, bus system is the only public transport mode available in the city, which accounts for a paltry 1.4% of all daily passenger trips; lower than almost any other similarly sized city (WB, 2015). To achieve the goal of emission reduction, long term and short term investment to improve capacity and service quality of public transportation is significantly important. Biofuels is known as a promising alternative fuel for road transport sector (Liaquat et al. 2010). Many countries have taken some initiatives to produce biofuels and enacted the law or declared biofuel policy to authorize the use of biofuels as major transport fuel in domestic market. With regard to Case 3, it is clear that there was a major reduction in the amounts of NMVOC, NOX, CO and SO2 emissions to 19.7%, 16.10%, 11.80% and 10.00%, respectively from the base year. There was a slight fall in the amounts of CH4 between the base year and the Case 3. The emissions decreased from 14.9 ktonnes (base year) to around 13.68 ktonnes (Case 3). In fact, the use of biofuels as a mean of increasing sustainability and a major alternative of petroleum based transport fuels has high prospect in Vietnam as Vietnam has strong agricultural sector to support biofuels production from energy crops. Not only do biofuel help the country step-by-step mitigate severely environmental pollution, but it also reduces the petroleum dependency.

4.2 Technological Solution – The Application

of Intelligent Transport System

Nowadays, motorized transport is a substantive major contributor to urban air pollution and it also becomes one of the main causes of global climate change. The past decade has seen a dramatic increase in the empirical investigation into the possible pathways for reducing the emission and pollutants of transport. These pathways consist of supporting low carbon technological innovation; encouraging modal shift from private car use to public transport or active travel like walking and cycling; developing several forms of traffic management and driving behavior; and implementing comprehensive strategies that mitigate travel demand. Not surprisingly, these solutions are developed based on behaviourally-orientated demand management strategy and they show their effectiveness in reducing emissions from transport.

However, researchers also argue that it is important to combine behavioral approach and technological innovation for providing more sustainable transport solutions (Anable and Shaw 2007; Chapman 2007; Rayner et al. 2008). Previous studies have quantified a range of benefits of intelligent technologies specifically Intelligent transport system (ITS) in decarbonizing (Grant-Muller and Usher 2014), lowering pollutant emissions and mitigating fuel consumption (Chen et al. 2011; Najjar 2013; Tsugawa and Kato 2010) (Tab. 4).

Recently, HCMC has started the application of ITS in traffic management. The government have recognized the importance of ITS where it is employed to enhance traffic signal control, traffic safety and transport infrastructure management. In the context of HCMC where traffic congestion, urban air pollution and climate change problem become worst, there is a need for employing ITS. This section thus highlights ITS techniques and technologies for the reduction of fuel consumption and minimization of the exhaust pollutant. A number of researches advocate that the ITS technologies play an increasingly important role in the drive for the fuel consumption reduction. According to (Barkenbus 2010), vehicle fuel consumption can be reduced through eco-driving and teleworking. Previous studies show that eco-driving including in-vehicle control and performance systems (Barkenbus 2010), in vehicle (overridable) speed control (Carslaw et al. 2010), or dynamic systems that utilize RTTI (Barth and Boriboonsomsin 2009) can reduce both fuel consumption and CO2 emission. Teleworking e.g. VANETs is crucial for ITS application and it influences the green measures. Since fuel consumption level depends much on different speeds, accelerations, stop-and-go times, routes, and the level of traffic congestion, VANETs collects the traffic data and transmits them to the driver in the roads (Oche et al. 2013). It is anticipated that 2.4% of CO2 emission from cars may be mitigated due to teleworking by 2050 (Santos et al. 2010). Since traffic congestion is one of the main causes of emission and air pollution, a number of ITS applications including Platooning, Intelligent Traffic Signal Control and Electronic Toll Collection Systems are developed to reduce the fuel consumption and exhaust pollutant. According to (Zabat et al. 1995), the platooning comprises a number of vehicles equipped with cutting-edge technology – one closely following the other and actively coordinates information. At a constant speed, vehicle consumes less fuel and emits less emission compared with stop-and-go driving. Platooning is considered as a fuel consumption-saver as the driver close together at a constant speed. This means lower fuel consumption and less CO2 emissions (Nieuwenhuijze et al. 2012). As one of several IST technologies, Intelligent Traffic Signal Control is developed to improve traffic flow, manage traffic speed among vehicles and low-speed modes at intersection. In addition, Intelligent Traffic Signal Control can reduce the stop-and-go traffic associated with congestion queue time resulting in less fuel consumption and less pollutant in traffic signal (Maslekar et al. 2011). Traffic congestion usually occurs at tollgate and as a result increases the

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exhaust pollutant. Toll Collection Systems is designed for electronic payment of highway and bridge tolls. It helps to eliminate the delay and save time by monitoring traffic and collecting toll electronically (Shaheen and Lipman 2007), which in turn reduces energy consumption and minimize the emitted pollutant by uninterrupted driving (Chen, Guha, Kwon, Lee and Hsu 2011; Maslekar, Boussedjra, Mouzna and Labiod 2011).

5. Result and Discussion

Motor vehicle has been identified as one of the largest emission sources in HCMC with subsequent adverse effects on urban health. The study estimated the emission inventory of road transport in the city by using EMISENS. Besides, emission reduction strategies were also identified by making comparison between emission levels of the base year and emissions generated from different scenarios. Overall, vehicle feet in HCMC released a relatively large amount of CH4 (14.91 ktonnes yr-1), CO (1763.71 ktonnes yr-1), NOX (547.52 ktonnes yr-1), SO2 (4.19 ktonnes yr-1), and NMVOC (193.62 ktonnes yr-1). The analysis also revealed that motorcycle and car are the major sources of air pollution; therefore, switching from motorcycle and car to public transport, using biofuels instead of petroleum based fuels and employing ITS in traffic management promise the substantial improvement in air quality. In recent years, policy makers have become aware of the need to mitigate the negative impacts of transport on environment. The imperative to reduce vehicle emissions has been accepted and enshrined as an objective in the policies. The findings of the study are expected to provide readers with a better understanding of emission levels in the city and to provide useful background to decision making.

Acknowledgements

We wish to thank Vietnamese German University and Technical University of Darmstadt that provided us with technical and financial support to conduct the research. Thanks also to the reviewer’s helpful suggestions in improving this paper.

Appendices

Fig. 4: EMISENS model and its input variable and output data.

Tab. 1: Hourly traffic volume (vehicle/h) anf Traffic fleet compisition (%).

Weekdays

(Monday-Friday)

7:00 8:00 9:00

Vehicle/h

% Vehicl

e/h %

Vehicle/h

%

Central district (urban main

street)

MC 1442

51

94.7

1636 97

94.9

16519 27

93.6

Car 737 43

4.8 776

12

4.5

757

10 4.3

Bus 67 3 0.5 108

6 0.6

303 10

1.7

Light

truck

67 5 0.4

Heavy

truck

Total

15228 42

100

17246 50

100

17646 68

100

Weekdays

(Monday-Friday)

16:00 17:00 18:00

Vehicle/h

% Vehicl

e/h %

Vehicle/h

%

Central district (urban main

street)

MC 13020 97

91.7

18715 65

94.2

20597 81

94.6

Car 974.00 6

6.9 968

6 5.1

1075 18

4.9

Bus 208

5 1.5

131 4

0.7 96 4 0.4

Light

truck

Heavy

truck

Total

14202 37

100

18914 49

100

21768 66

100

Weekdays

(Monday-Friday)

7:00 8:00 9:00

Vehicle/h

% Vehicl

e/h %

Vehicle/h

%

Urban MC 13342 95. 13985 95. 14002 95.

Street name: Road No.7, Nguyen Van Kha St., National Road No. 22. Type: Rural street Zone: Suburb

Road condition: 2-way street, old motorcycles and truck were observed.

Street name: Nguyen Kiem St., Nguyen Trong Tuyen St., Hoang Van Thu St. Type: Urban secondary street Zone: Urban district Road condition: 1-way street, narrow and busy street.

Street name: Nguyen Thi Minh Khai St., Hai Ba Trung St., Nam Ky Khoi Nghĩa St. Type: Urban main street Zone: Central district Road condition: 2-way street, busy and heavily congested street.

Fig. 5: Study areas in 3 different zones.

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district (urban second

ary street)

53 8 56 9 62 0

Car 538 38

3.9 546 21

3.7 551 25

3.7

Bus 41 2 0.3 53 4 0.4 101 5

0.7

Light

truck

88 4 0.6

Heavy

truck

Total

13921 45

100

14584 53

100

14742 61

100

Weekdays

(Monday-Friday)

16:00 17:00 18:00

Vehicle/h

% Vehicl

e/h %

Vehicle/h

%

Urban district (urban second

ary street)

MC 13107 23

95.1

15098 44

95.3

15131 27

95.7

Car 438 20

3.2 507 19

3.2 482 28

3.0

Bus 132 7

1.0 112 2

0.7 103 6

0.7

Light

truck

Heavy

truck

Total

13779 37

100

15842 32

100

15813 45

100

Weekdays

(Monday-Friday)

7:00 8:00 9:00

Vehicle/h

% Vehicl

e/h %

Vehicle/h

%

Suburb (rural street)

MC 4047 22

61.7

4211 17

54.5

5763 20

65.9

Car 121 14

1.8 159 4

2.1 161 6

1.8

Bus 8 1 0.1 7 1 0.4 78 2 0.9

Light

truck

93 2 1.4 90 1 1.5 232 11

2.7

Heavy

truck

2287 10

34.9

3208 14

41.5

2510 23

28.7

Total

6556 31

100

7675 37

100

8744 36

100

Weekdays

(Monday-Friday)

16:00 17:00 18:00

Vehicle/h

% Vehicl

e/h %

Vehicle/h

%

Suburb (rural street)

MC 4277 13

57.5

4431 12

59.7

3100 25

47.6

Car 113 4

1.5 101 2

1.4 82 3 1.3

Bus 65 2 0.9 33 1 0.4 22 1 0.3

Light

truck

194 7

2.6 211 5

2.8 190 4

2.9

Heavy

truck

2795 10

37.5

2650 8

35.7

3117 17

47.9

Total

7444 29

100

7426 31

100

6511 27

100

Tab. 2: Emission inventory from traffic sources for the year 2016 (ktonnes).

Emissions

Car Motorcycle

Light

truck

Heavy

truck

Bus

Total

Total Uncerta

inty (%)

CH4 5.04

8.23 0.72 0.81 0.11

14.91

58.00

CO 757.8

959.01 17.07

21.11

8.72

1763.71

42.40

NOX 189.8

98.35 101.18

122.03

36.16

547.52

32.76

SO2 0.5 2.11 0.4 0.83 0.35

4.19 34.07

NMVOX

86.26

101.03 2.01 3.11 1.21

193.62

47.37

Notes : The uncertainty reflects the variation of input parameters (i.e. different vehicle category, speed, temperature, street lane, hour

street mileage)

Tab. 3: Annual emission (kt yr-1) under base case 2016 and emission strategies scenarios.

Emissions

Base case

Emission (kt yr -1) Reduction (%) Case

1

Case 2

Case 3

Case 1

Case 2

Case 3

CH4 14.91 12.8 11.91 13.68 14.15

20.12

8.20

CO 1763.71

1688.3

1714.01

1556.21

4.28 2.82 11.80

NOX 547.52

468.74

542.5 459.62

14.39

0.92 16.10

SO2 4.19 4.08 4.09 3.79 2.63 2.39 10.00

NMVOX

193.62

185.5

173.47

155.47

4.19 10.41

19.70

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Tab. 4: Summary of ITS applications.

Authors ITS

technique

and

technologies

Energy/emission impacts

(Shaheen and Lipman 2007)

Electronic toll collection System (ETCS)

Saves time; Reduces energy consumption and emissions by reduce the stop-and-go traffic; Maintain a constant speed in toll gate; Savings of 1.2 million gallons of fuel per year due to reducing the delays at toll.

(Santos, Behrendt and Teytelboym 2010) (Oche, Noor, Al-jawfi, Bimba and Nasir 2013; ZHANG. X 2007)

Teleworking Collects the traffic data and transmits them to the driver in the roads; Reducing traffic congestion, traffic accidents; A reduction of 2.4% of emission by 2050.

(Santos, Behrendt and Teytelboym 2010)

Vehicle Navigation System (VNS)

Help drivers choose the shortest and environmentally friendly routes; Reduces emissions by 20%.

(Santos, Behrendt and Teytelboym 2010) (Zabat, Stabile, Farascaroli and Browand 1995)

Platooning

Reduce stop-and-go driving; Maintain constant speed; Fuel savings and emissions reduction, ~ 20%.

(Barkenbus 2010; Barth and Boriboonsomsin 2009; Carslaw, Goodman, Lai and Carsten 2010; Santos, Behrendt and Teytelboym 2010)

Eco-driving: (In-vehicle control and performance systems, in vehicle (overridable) speed, control, dynamic systems that utilise RTTI.

Fuel savings 5%-10%; A reduction of 6%-20% emission;

(Midenet et al., 2004; Rakha et al., 2000; Rakha et al., 2000)

Intelligent Traffic Light Control System.

Improve traffic flow; Manage traffic speed among vehicles and low-speed modes at intersection; Reduce the stop-and-go traffic; Fuel savings 1.6% to 50% percent; 4% reduction of emissions in peak traffic.

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climate change initiative. Energy policy, 2010, 38(2), 762-769.

[3] BARTH, M. AND K. BORIBOONSOMSIN Energy and emissions impacts of a freeway-based dynamic eco-driving system. Transportation Research Part D: Transport and Environment, 2009, 14(6), 400-410.

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[5] BOULTER, P. AND I. S. MCCRAE The links between micro-scale traffic, emission and air pollution models. Edtion ed.: TRL Limited, 2007. ISBN 1846086728.

[6] CARSLAW, D. C., P. S. GOODMAN, F. C. LAI AND O. M. CARSTEN Comprehensive analysis of the carbon impacts of vehicle intelligent speed control. Atmospheric Environment, 2010, 44(23), 2674-2680.

[7] CHAPMAN, L. Transport and climate change: a review. Journal of transport geography, 2007, 15(5), 354-367.

[8] CHEN, W., R. K. GUHA, T. J. KWON, J. LEE, et al. A survey and challenges in routing and data dissemination in vehicular ad hoc networks. Wireless Communications and Mobile Computing, 2011, 11(7), 787-795.

[9] DUNG, H. M. AND D. X. THANG Estimation of emission factors of air pollutants from the road traffic in Ho Chi Minh City. VNU Journal of Science: Earth and Environmental Sciences, 2008, 24(4).

[10] EKSTRÖM, M., Å. SJÖDIN AND K. ANDREASSON Evaluation of the COPERT III emission model with on-road optical remote sensing measurements. Atmospheric Environment, 2004, 38(38), 6631-6641.

[11] GRANT-MULLER, S. AND M. USHER Intelligent Transport Systems: The propensity for environmental and economic benefits. Technological Forecasting and Social Change, 2014, 82, 149-166.

[12] GREGORY, D., O. MCLAUGHLIN, S. MULLENDER AND N. SUNDARARAJAH. New solutions to air pollution challenges in the UK. In London Forum for Science and Policy Briefing Paper. London: Grantham Institute. 2016.

[13] GULIA, S., S. S. NAGENDRA, M. KHARE AND I. KHANNA Urban air quality management-A review. Atmospheric Pollution Research, 2015, 6(2), 286-304.

[14] HO, B. Q. AND A. CLAPPIER Road traffic emission inventory for air quality modelling and to evaluate the abatement strategies: A case of Ho Chi Minh City, Vietnam. Atmospheric Environment, 2011, 45(21), 3584-3593.

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[15] HO, B. Q., A. CLAPPIER AND G. FRANCOIS Air pollution forecast for Ho Chi Minh city, Vietnam in 2015 and 2020. Air quality, atmosphere & health, 2011, 4(2), 145-158.

[16] KOTA, S. H., H. ZHANG, G. CHEN, G. W. SCHADE, et al. Evaluation of on-road vehicle CO and NOx National Emission Inventories using an urban-scale source-oriented air quality model. Atmospheric Environment, 2014, 85, 99-108.

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DECISION MAKING RULES AND THE INFLUENCE OF MEMORY DATA

Vaclav BERAN 1, Marek TEICHMANN 2, Frantisek KUDA 2, Natalie SZELIGOVA 3

1Department of Economics, Faculty of Economics, University of South Bohemia in Ceske Budejovice, Studentska 13, 370 05 Ceske Budejovice, Czech Republic




Abstract. The evolution of processes in technical-economic structures is generally considered to be complex, chaotic and mostly a cumulation of a myriad of dynamic forces. The development of computational techniques over the past century enabled the application of computing power to economic questions, which has been a trend since the 1950s. In particular, computational analysis has become more widespread since the collapse in the economy following the financial crisis of 2007/08. The debate encompasses the application of commonly used complex simulations, which are considered to be useful to predict tomorrow's world with good accuracy. Some authors claim that the economics and finance industry and risk management, in particular, need advanced and detailed mathematical models.

Keywords

Decision making, decision rules, data memory, utility, decision space, cellular automata.

1. Introduction

Cellular automata (CA), which can be used to represent patterns, are shaped by an initial state. The initial state represents the initialization as an invention, innovation or investment (etc.). The initial state is determined by assigning a starting position for a cell in time sequence t=1, 2, 3, … , m as utility value u(t). Any new generation of an outcome is created by following a permanent logical economic decision rule. The rule is a function that determines each cell in the new ex –ante states on the basis of the state(s) of the current short-term ex-post situation in its past neighbourhood. Typically, the rule for updating the state of cells is the same for each cell and does not change over time [1].

2. The decision process – decision rule horizon and decision rule memory

The decision process is constituted of a) decision making rules D, b) a decision space S, c) the decision data structure (M, memory data, which is data about past decisions), d) the evaluation of the decision space position (U, utility). The decision criterion (i.e. the decision rule) generates (i.e. forms) the decision space. In the present paper, the economic applications are illustrated as a 2D space for economic decision making with time (sequence i = 1,...,m) as one dimension and activities (j = 1,...,n) as the second dimension [2]. The calculation of the benefit of activity Aij in the decision space is assessed in terms of utility uij (i.e. it is awarded this utility). The assessment in decision making requires the calculation of an evaluation function Φ. The evaluation function creates values u(i,j) and these represent the economic interpretation, that is, they are ex post values for present state data. The result is matrix U, which covers the decision space ij, as presented in (1).

𝑼 = [ 𝑢1,1 ⋯ 𝑢1,𝑗 ⋮ ⋱ ⋮ 𝑢𝑡,1 ⋯ 𝑢𝑡,𝑗⋮ ⋱ ⋮𝑢𝑚,1 ⋯ 𝑢𝑚,𝑗

⋯ 𝑢1,𝑛 ⋱ ⋮⋯ 𝑢𝑡,𝑛⋱ ⋮⋯ 𝑢𝑚,𝑛] (1)

The decision rules, D, have a broad interpretation in this article. The D rules might be defined geometrically or as mathematical functions or statistical data. They may have a logical structure and they may represent economic rationality or aesthetic principles, among other things. In the most practical applications, the rudimentary decision criteria shape the space in time, which is described here as dynamic development. In the multifaceted socio-economic environment that we perceive as a dynamic process, we





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recognize decision rules (criteria) as a dominant element.

For example, it is true that during different time periods, the same set of rules can lead to massively different results. Specifically, rules may lead to a certain outcome in the context of long term decision making. In economics, decision rules typically serve the pragmatic purpose of selecting a goal, setting preferences, selecting options, identifying alternatives, representing regulatory requirements and other acts of predominantly short-term execution. The substantive impact on decisions is the fuzzy time horizons (short, medium, long-term). Economic decision criteria are predominantly based on defined logical conditions and mostly relate to a common transition rule [3].

In an economic context, a decision rule is related to ex-post events, which are events with an evaluated history. In other words, the data memory is fixed to time (t-τ). If decision criteria use data from the past to develop a decision rule with memory, the assumption is typically made to implement the decision rule based on general formula, such as:

IF ((D is true) then (evaluation Ai as 0) else (evaluation Ai as ui(t,j))

(2)

where D represents the decision rule, Ai (t,j) is activity j occurring in time t. Every space element (t, j) may host activities Ai, i=1, …, k or remain empty. The decision rule differentiates the suitability of location (t, j) for activity Ai from the range of possible activities i=1, …, k. At time t and for activity j, utility can be evaluated as:

ui(t, j) = F(Ai(t,j)│N) (3)

where N is the selected neighbourhood of the cell (t, j) and F is an arbitrary function specifying the utility value for the cell location.

3. Research question

The essential question is to what extent the construction of the decision rules influences the decision space and how intensively the data memory might influence the decision space. If data history significantly shapes the decision space, there is a need to give careful consideration to this information. Stored data about the past are relevant for the present and might shape the decision space for the future.

Real data sources typically represent a technical-economic process. For the purpose of this analysis, we substitute a real process with CA. Further, we identify the process as a fractal created on the basis of decision rules [4]. It is assumed that the decision rule is implemented into a process, according to expression (1), whereby this expression is a general schematic model which can be applied to most activities in a technical-economic context.

The typical examples of interpretations of this analytical approach are life governing rules that factually form a dynamic process. The sequence (i.e. the dynamic) of time

and space is often considered to be defined by increasing completeness and efficiency. However, it is not clear whether this is actually the case. Accordingly, the main focus of this paper is to shed light on this.

4. Conclusions

The decision space is not homogenous for the rules modelling real-life situations which were examined in this paper (α, β, and γ). A range of productive periods of DRαβγ exist, as do a range of fully unproductive time periods, which exhibit a lack of utility. The decision space creates bubbles which cover substantial areas of the decision space. These bubbles represent the absence of usability. Moreover, the decision space affects the utility (productivity) of subsequent time periods and in the long term, partially affects the activities Ai which can be considered. That is, the productive space on various subsequent levels is affected. Decisions which choose an appropriate action in an appropriate time period leads to a higher utility being generated [5].

Acknowledgments

This work was supported by funds for the Conceptual Development of Science, Research and Innovation for 2020.

References

[1] Aumann, R. (1974): Subjectivity and correlation in randomized strategies, Journal of Mathematical Economics 1, 67-96.

[2] Ball, P. (2008): Cellular memory hints at the origin of intelligence. Nature, 451, 385.

[3] Mandelbrot, B., Taleb, N., (2006): A Focus on the Exceptions that Prove the Rule. Financial Times, Friday March 24.

[4] Mandelbrot, B., B., Hudson, R., L., (2004): Misbehaviour of Markets. Basic Books, New York.

[5] Taleb, N., (2008): Fooled by Randomness: The Hidden Role of Chance in Life and in the Markets. Random House Publishing Group, New York.

http://en.wikipedia.org/wiki/Complexity

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DYNAMICS OF REGIONAL DEVELOPMENT IN REGIONAL AND MUNICIPAL ECONOMY

Vaclav BERAN 1, Marek TEICHMANN 2, Frantisek KUDA 2, Renata ZDARILOVA 2, Natalie SZELIGOVA 3

1Department of Economics, Faculty of Economics, University of South Bohemia in Ceske Budejovice, Studentska 13, 370 05 Ceske Budejovice, Czech Republic




Abstract. This article deals with dynamics of territory development in regional and municipal economy. The development of the territory is and has always been limited or restricted by the available sources of capital, the dynamics of its use, the localization of its distribution in the chosen territory. Today's limits are in Czech conditions laid down by the Building Act, namely the land-use plan, the strategic plans for development and the political mechanisms of the electoral lecturer. The verbalization of the democratization of the economy is swept by the concepts of meritocratic holding and admission to create values, but also to already existing values. Interpret the term values as infrastructure developed in the past, but also as resources given by the natural, geographic and other environments.

Keywords

Regional development, optimisation, investment budget, time limits, utility.

1. Introduction

Regional development is an important topic of many groups as in [1, 2] is mentioned. It is the subject of a whole range of ideas, publications and verbalizations, as well as of many faults and mistakes. According to [3-7] there are changes in thinking, approaches and strategies for the purpose of strengthening the path leading to rational use of resources. In general terminology the urbanization of

regions [8] implies the protection of cultural and other values that should have considerate and respectful stance towards nature and fauna and flora, data of quantification as [2] mentions. The fact is, however, that we do not know what limits are defined by optimal solutions.

If we favour quantization and the dynamics of quantification, basic is the creation of values and benefits flowing from the implemented capital. A new perspective-view on Capital can be found in a number of papers, and analyses. The robust work [1] deals with the topic and has achieved extraordinary success. It seeks, inter alia, to deal with the temporal dynamic aspect of the phenomenon of capital and its metamorphoses in the 21st century.

2. Optimization prerequisites - Investments & Budgets

Return-oriented capital is indisputably tied up, as a tool, with benefits to the capital-holders. The publication [9], also referred to as alias 21st century, has focused on numerous arguments about the accelerating growth of inequality in the distribution of capital returns. The author has introduced a label for growth as g rate. Beneficiaries of economics growth are regions, citizens, urban areas, more in [1]. However, the extent and method of distribution is a separate issue. Undoubtedly, for the creation of capital, the resources used derive from the breakdown of net outputs of the macroeconomic unit. They are referred to as savings and marked as s.

A monograph author [9] emphasizes long time existing inequalities s > g as critical and over long term






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unsustainable disparity. Situation where inequalities growth s >> g significantly dominates the economy leads to a degradation of ability of the economic unit to create outputs, let us denote them Y. Disparity of inequalities of benefits from outputs Y and production of the capital K disrupts relations in the social sphere, followed by a degradation of efficacy factors such as performance, productivity and efficiency of resources used. Internal relations, generally represented as democratic, however, contain meritocratic features. They are used mainly in the area of the distribution of benefits, and consequently in the damaged social development [10]. The concept presented [9] points out an increasing disproportion in relation s >> g. The disparity is illustrated by a large set of statistical data of last centuries, the persuasiveness of arguments based on long-term time series. The argument of the long-term growth in imbalances results in finding that a balanced relation between the growth revenues on capital employed of times series Kt and output performances of the economic unit Yt should be better balanced. Let us denote the factor which counterbalances them as the saving rate s from outputs Yt against the rate of share g of the capital.

However, we operate in a macro-economic notion, and with its assumptions affected by volatility in the micro-economic implementation, the differences in a range (±) are the result of disparities in the adherence to the basic rules of growth of an economic unit: resources (investments) can be made only where they will generate gain (establish the ability to realize deferred consumption, i.e. additional new savings).

This creates a growth spiral cycle of using savings for future investment purposes. A prerequisite for the notional growth spiral is that the new It+x will generate revenues ṽ higher than those of existing investments. In the opposite case, the new investment would be a simple renewal and establish the cycle of a degradation process.

Interpretation of the stated claims requires their projection into microeconomics, or to formulate rigorous answers to two microeconomic questions: to what extent it is obligatory to adhere to:

1. Investment limit,

and to what extent it is binding to require adherence to

2. Limit period for return on invested capital.

2.1. Maximal limit payback time of invested resources

The invested resource on the one side is directly invested capital. At the same time, assets are pledged to cover risks, reserves, financial guarantees and liabilities arising from unexpected situations. Generally, capital and other resources are bound for the duration of the settlement of the obligations from the realization of an unfinished investment unit.

The commercial return limit is considered to be a relationship based on the commercial rate of required

annual returns i (interest on bank loans) and the valuation of the commercial risks of the project r, it applies that:

teko = 1/(i +r) (1)

We calculate the investment capital required as: Ieko = teko ṽ (2)

By analogy, it is possible to quantify partial limits of project and implementation:

tpro = 1/(i +r +rpro) (3) treal = 1/(i +r +rpro +rreal) (4)

Consequently, the investment limits in terms of the relationships (3), (4) and (6) correspond to the acceptability of the investment cost range. To enter a new investment, upgrade, or renewal it applies that:

treal ≤ tpro ≤ teko ≤ tmax (5)

and subsequently

Ireal ≤ Ipro ≤ Ieko ≤ Imax (6)

3. Methods of economic - technical breakdown of investment development projects of the region

Projects that require corrective adjustments or rejection become investment projects that do not generate benefits for a regional entity. If the rules are not respected, this is a failed, emergency situation project. It establishes a space for non-compliance with production, construction, economic parameters, and legal and environmental standards. States of emergency arise with delays at various stages of the investment life cycle. These include life-cycle reduction, failure to deploy anticipated capacities, malfunctions, excessive maintenance, downtime, premature renewal cycles, and more.

Investment projects as development tools are intended to operate in the long term. They require a functioning infrastructure and a rational choice of possible solutions. This is the domain of decision-making methods. It also undeniably includes the selection of investment plans, proposals and their method of implementation. The decision-making methods used lie with each qualification and choice of variable and alternative solutions. Decision-making methods undeniably have their use hierarchy (from defining the basic economic framework of the project to handing over the investment unit for use). Violation of basic rules is an intervention in the economics of the investment project and creates the prerequisites for an economic emergency of the project, the need for modifications, restrictions in the course of use of the investment and the need for new, redevelopment costs. Examples of this can be investments that were not completed in time, or exceeded costs based on future revenues.

Decisive methods within the economic framework are,

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from the perspective of methods, multifaceted, and further, also should govern the process procedures of investors.

3.1. Illustrative Data – Examples For a current illustration, we can present the Flughafen Berlin Brandenburg (BBA) project. Benefits include expansion of capacity, modernization of operating technologies, safety, and more. The project will undoubtedly be completed in high quality, but fulfilling its economic recuperation will be challenging and long-term [11-14].

4. Results and discussion – Investment and Optimalization of Land Use Plan Infrastructure

The idea of a liberalized model of assessment of public investment development is applied mainly on the expenditure side of public budgets. If we consider the revenue side of public budgets and decide to obtain their valuation, we will need a balanced optimization calculation. Here we will appreciate the informative power and application of the previously mentioned relationships. Designing projects that do not generate positive revenue streams leads to project degradation and questioning of a project’s economic or material justification.

The development of territorial units is undoubtedly composed of successful localization of effective component investment solutions. They should create benefits in the area. Localization in an area with unacceptable Δ(⸱) generates an increase in costs, almost all in parallel with the extension of execution time. The development of regions is linked to a number of diverse and parallel projects in the financial year. Their arrangement is professionally addressed by urban planning.

Nevertheless, in many cases in practice, it is possible to find regrettable violations of fundamental rules. Decrease of yields and extension of commissioning dates are almost a general problem in the implementation of projects to support regional development. Existing practice in the EU is looking for a way to implement more effective mechanisms for compliance with project award conditions – which is overwhelmingly quite difficult.

4.1. Optimizing Procedures and their Limits

Territorial units and their budgets can be segmented into individual localized parts. Thus, the first prerequisite for using optimization is met. The individual investments receive their time specification according to the availability (release) of investment funds. Implementation mechanisms are annual budgets, territorial implementation priorities and technical conditions.

Land-use planning works with land-use planning documentation, makes available areas for individual activities to avoid collisions in their operation and use.

4.2. Analysis – Calculation of Achievable Limits

The answer to the question of what benefit thresholds can be achieved in a given territory can be found using optimization calculations, it is possible to follow the interpretation from the optimization application. The valuation of the benefits of an optimized (limit) solution is shown on the vertical axis. This is an illustrative example of a district city segment. The area of benefits is fragmented and shows the differences in potential benefits with small changes in investment locations.

Generally, in the optimization of benefits, in the area of the territory defined as matrix A, such a proposal xo occupancy of the individual available areas of the territory (i, j) is sought, which maximizes the total return (benefit). At the same time, the applicable land use restrictions are respected. These include, for example, the extent of public investment, their structure, the volume of investment capital invested and its ownership structure. The formulation of the optimization task is mainly based on respect for material continuities. These can be referred to as follow-up processes N to which a specific function of maximization (benefits, revenues, profits, etc.) is linked.

The output of the optimization calculation is the limit of the potential target solution. The choice between proposals allows for a prediction of the degree of efficiency interpreted as capital, efficiency, value of the goal. The evaluation of options, within the design of the chosen solution, enables indicators of effectiveness. Comparing proposals and their variant solutions serves to trace and eliminate weaknesses, quantify the benefits achieved, and make changes more effective. It is an independent technical and economic issue of the use of optimization calculations.

Decision-making in the time-limited phases with variant designs is a challenging decision-making task. In real tasks, its sophistication increases by assessing the practically achievable maximum and mathematically formally determined optimal solutions. Indicators of effectiveness and efficiency of invested resources can ensure orientation in the strengths and weaknesses of individual variant proposals. This deepens the understanding of the rationality of management interventions for monitoring development.

5. Conclusion

Optimization calculations allow you to define limits of achievable benefits. The use of the calculations can be seen especially in the assessment of the design of the spatial arrangement (urban design), the comparison of alternative solutions, the comparison of alternative solutions of the

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chosen alternative, the assessment of the benefit structure from the draft annual budget, the evaluation of alternatives and the benefit options for budget proposals and other qualitative and quantitative parameters linked to the development of the territory. The spatial plans create a structure of land use, analyse land-use planning data and produce studies of possible solutions to specific problems (infrastructure, ecology and others). Investment economic frameworks and optimization documentation can, in a number of cases, facilitate decision-making on the direction of investment support for development and simplify the argumentation on the effectiveness of the proposed controlling interventions [15].

Acknowledgments

The work was supported by funds for Conceptual Development of Science, Research and Innovation for 2020 allocated to VŠB - Technical University of Ostrava by the Ministry of Education, Youth and Sports of the Czech Republic.

References

[1] Hirschmann, A. O. The Strategy of Economic Development. New Haven : Yale University Press, 1958. ISBN 0-8133-7419-7.

[2] The World Bank. World Development Indicators 2014. Washington DC : International Bank for Deconstruction and Development, 2014. ISBN 978-1-4648-0164-8.

[3] Samuelson, P. Foundations of Economic Analysis. Cambridge : Harvard University Press, 1947. ISBN 9780674313033.

[4] Dlask, P., Beran, V., Matejka, P. Optimization and decision making in development area. Prague : CVUT, 2012. ISBN 978-80-01-04978-5. (in Czech)

[5] Brock, W.A., Xepapadeas, A., Yannacopoulos, A. N. Optimal Control in Space and Time and the Management of Environmental Resources. Annual Review of Resource Economics. 6, 2014, Sv. 33-68, ISSN 1941-1340.

[6] Gregire Normand. EU economies hit by collapse in investment, new data shows. LA Tribune. Euro and Finance, 2018, collected 16. 5.2018.

[7] Holman, R. et al. History of Economic Thought. Prague : C. H. Beck, 2005. ISBN 80-7179-380-9. (in Czech)

[8] Weigrich, K., Kostka, G., Hammerschmid, G. The Governance of Infrastructure. Oxford : Oxford University Press, 2017. ISBN 9780198787310. Available at doi:10.1093/acprof:oso/9780198787310.001.0001.

[9] Piketty, T. Capital in the Twenty-first Century. Cambridge Massachusetts, London : The Belknap Press of Harward University Press, 2014. ISBN 978-0-674-43000-6.

[10] Boushey, H., Bradford DeLong, J., Steinbaum, M. After Piketty. Cambridge Massachusetts, London England : Harvard University Press, 2017. ISBN 9780674504776.

[11] Delius, M. Bericht des 1. Untersuchungsausschusses des Abgeordnetenhauses von Berlin. 2016, Abgeordnetenhaus Berlin, Drucksache 17/3000, 443 pp. (in German)

[12] Berliner Zeitung. BER - Baustelle. B.Z. - Berlin. [Online] B. Z., 3. 9 2013. [cit: 17. 10 2017]. Available at: https://www.bz-berlin.de/artikel-archiv/ber-baustelle-66-500-mal-pfusch. (in Deutch)

[13] Lutte, R. BER Flughafen Kabel. bz-berlin. [Online] 28.. Sept. 2015. [cit: 11. 04. 2018] https://www.bz-berlin.de/media/ralf-lutter-300. (in Deutch)

[14] Santamaria, O. G. R. Analysis of Delays in Construction Tasks. Prague : CTU, 2012.

[15] OECD. OECD Regions and Cities at a Glance 2018. Paris : OECD Publishing, Paris, 2018. ISBN 9789264305090. Available at doi.org/10.1787/reg_cit_glance-2018-en.

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AN ANALYSIS OF TRAFFIC CONFLICTS AS A TOOL FOR SUSTAINABLE ROAD TRANSPORT

Vladislav KRIVDA1, Jan PETRU1, David MACHA1, Kristyna PLOCOVA1, David FIBICH1

1Department of Transport Constructions, Faculty of Civil Engineering, VSB – Technical University of Ostrava, 17. listopadu 2172/15, Ostrava, Czech Republic


Abstract. The paper deals with solving a partial issue within the scope of sustainability of road transport, and it is the issue of potential accidents, i.e. traffic conflicts. First, there is introduced a method for the analysis of traffic conflicts using video equipment. The attention is focused on traffic conflicts that happen at turbo-roundabouts. Given the diversity of causes of traffic conflicts, the emphasis is placed on the correct identification of the cause, i.e. whether the traffic conflict is caused only by the negligence of the road user, or whether the conflict is more or less influenced by an inappropriately designed intersection, or its specific building element (e.g. unsuitable corner radius, absence of safety elements, etc.). The next part of the article presents a selection of obtained results, which emerged from analyses performed at about 100 turbo-roundabouts in 9 countries of Europe. The illustrative diagrams show the courses of the emergence of traffic conflicts, the causes of which are then described in details. The conclusions from these analyses confirm the main hypothesis that the analyses of traffic conflicts should be an essential part of designing of roads in order to increase the safety on roads and, last but not least, also within the context of sustainable transport.

Keywords

Road Traffic, Road Transport, Traffic Conflict, Traffic Safety, Turbo-Roundabout.

1. Introduction

Within the sustainable transport, the effort is to supress its negative effects as much as possible. The classic approach to traffic planning usually primarily seeks to maximize the level of mobility. On the other hand, for sustainable development, the transport should be means and not the

goal. It is necessary to design cities and transport infrastructure so that the unnecessary traffic is reduced. There are a number of methods for solving sustainable transport, but it always depends on the specific type of the transport, the given locality, local customs and possibilities (especially spatial and economic), etc.

The suggested solutions within the sustainable transport must also be reflected in designing of transport structures. Technical standards are often outdated and provide solutions that may not be compatible with sustainable transport. For example, when designing intersections on roads, the designers often rely only on common types of intersection, but those do not have to cope with the requirements placed on them. In general, the design of an intersection represents a number of activities, i.e. for example, the performance of traffic surveys, the drawing of the intersection, the verification of the passage in the intersection using swept paths, verification of the capacity, or creation of a microsimulation transport model, etc. Even if all design principles and technical standards are observed, dangerous behaviour of road users can occur at the intersection. However, the drivers may not always be responsible for it. There exist certain hidden factors that even an experienced designer cannot predict in advance [1]. Not until the real traffic reveals whether the intersection is designed properly. Often even a small detail can play an important role. For example, an improperly designed building element (insufficient corner radius, improperly located traffic island, etc.) can cause incorrect behaviour of the driver. For example, with a small corner radius, the driver of a larger vehicle can either drive the rear wheel onto the curb of the corner, or due to an effort to prevent the driving onto the curb, the driver will leave the intersection in the opposite direction. Here arises the question whether it is entirely a fault of a driver, or whether the incorrectly designed corner is also partially responsible for this situation.

To reveal these problems, there is, for example, an analysis of the behaviour of the road users, in other words, the analysis of traffic conflicts, which is the main topic of this






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article. This analysis looks for those details in the design of the intersection (or other place of transport) that may affect the inappropriate or even dangerous behaviours of the drivers. It can be used, for example, to monitor dangerous overtaking or non-compliance with permitted speed [2], wrong manoeuvre while parking the vehicles [3] or it can focus only on the behaviour of a certain group of drivers, e.g. of lorries [4], or to a limited extent it can be used when analysing the suitability of the monitored place for passage of oversized cargos [5].

The submitted article deals with the analyses of traffic conflicts at sc. turbo-roundabouts – see Fig. 1. Turbo-roundabout is a special type of roundabout that has two or more spirally constructed lanes on the roundabout. The principle of the geometric arrangement of the roundabout is to ensure vehicles a smooth passage from the entrance of the roundabout, through the roundabout to the exit in one lane without the need to change the lane. One of the important elements of the turbo-roundabout is the possibility of physical separation of lanes (Fig. 1 – no. 1 and 3), whereas at the beginning of the roundabout there may be sc. spike (no. 2). This physical separation of lanes has a major impact on the safety of the traffic at the turbo-roundabout, as described later in this article.

Fig. 1: An example of chosen type of turbo-roundabout.

Turbo-roundabout is a type of a roundabout, which is generally considered to be a suitable solution for busy intersections, both in terms of capacity [6,7] and also in terms of safety [1]. In some European countries (e.g. the Netherlands, Poland, Hungary) this type of a roundabout is quite common, in other countries (e.g. Austria, the Czech Republic, Slovenia, Slovakia) the turbo-roundabouts are more or less rare. As a part of the research in years 2014 to 2019, the authors of this article analysed 105 of turbo-roundabouts out of a total of approximately 600 turbo-roundabouts in Europe. The analysed turbo-roundabouts were in 9 countries (Great Britain, the Netherlands, Germany, Luxembourg, Austria, Poland, Slovenia, Hungary and the Czech Republic).

Although most of the analysed turbo-roundabouts complied with the regulations, there were many traffic conflicts at them. These were both the mistakes of the drivers, and also problems caused by improperly designed building elements. Research has shown that the video analysis of conflict situations is a suitable method for analysing the dangerous hidden factors that can be the cause of accidents at turbo-roundabouts.

2. Used methods

A number of methods were used to analyse traffic conflicts. The chosen methods that were used for the analysis of conflicts at turbo-roundabouts will be described in this chapter. There are basically two main areas:

• Adding of traffic intensities using various technical devices, either directly (automatic counters) or indirectly (detecting intensities from video recording).

• Video analysis of traffic conflicts (when using video recordings from which the intensity of the transport was also measured in some cases).

For adding the intensities of traffic, the NU-METRICS NC-200 counting cards were used. They are used to detect the number, speed and type of vehicle using the VMI (Vehicle Magnetic Imaging) technology. Further, the VIACOUNT II and ICOMS TMS-SA adding devices were used. Both devices use Doppler radar to detect vehicles. Each of the mentioned types of devices has its limits, which are specified e.g. in [8]. For these reasons, a combination of individual devices was used, which was subsequently installed on the chosen monitored turbo-roundabouts.

Standard video cameras and special cameras, such as GoPro and Lamax outdoor cameras were used to record video of the traffic at the turbo-roundabout, which were besides others, mounted on a moving vehicle (on the front or on the roof), front and rear car camera, Insta 360 camera, enabling recording in 360o, etc. In this way, it was possible to monitor and record traffic, both in detail and in a broader context. Different types of UAV (DJI F450 drones, MAVIC 2 ZOOM, 210 RTK and Phantom 4 Pro V2) were used for more detailed analysis of turbo-roundabouts. By this, it was possible to accurately analyse the construction layout of the roundabout and traffic engineering data. It was not possible to obtain this information from ground measurements (better angle of recording, larger scope of observation, etc.).

For the analysis of traffic conflicts, the own method was used, which uses, among other things, video equipment. This method is a part of a certified methodology [9]. If we use the definition from [9], or from [10] then a traffic conflict is an observable situation in which two or more road users approach each other in space and time to such an extent that there is a risk of a collision, if their movement does not change. Video analysis of traffic conflicts is described in detail, e.g. in [1]. For relevant results, it is necessary to monitor a number of parameters for each traffic conflict. The most important is the seriousness of the traffic conflict and the reason of the origin of the traffic conflict.

The seriousness of the traffic conflict can be divided into three basic types:

• 1st level of seriousness – a situation where it is about a violation of traffic regulations at that time

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by a lone road user, i.e. without the presence of others who could be limited or endangered (it is sc. potential traffic conflict)

• 2nd level of seriousness – a situation when a certain disruption of the smooth transport can be observed, i.e. situations which do not provoke a violent reaction by other participants, but it is a hesitation or a single misconduct which results in a reaction of other participants,

• 3rd level of seriousness – a situation where only a rapid evasive reaction (e.g. a sharp braking or sudden deflection) prevents a collision,

• if an accident happens, we mark this situation with the number 4.

According to the reason of the traffic conflict, we divide the traffic conflicts into:

• operational traffic conflicts – a traffic conflict caused only by the driver (or another road user),

• construction traffic conflict – a traffic conflict caused not only by the driver, but also (and mostly mainly) by improperly designed building elements.

As a quantity giving us a certain idea about the degree of danger of traffic at the observed roundabout is sc. relative conflict indicator CRW [TC/100 veh.]:

100..

V

CNC

STC

RW= , (1)

where NTC – is a number of traffic conflicts (TC) in an hours [TC/h], CS – coefficient of seriousness of the traffic conflict [-], V – hourly intensity [veh./h], veh. - vehicle. Indicator CRW then shows the number of traffic conflicts for 100 vehicles that passed in the given time of measurement.

3. Results of analyses

Table 1 shows the most common types of traffic conflicts that were observed at turbo-roundabouts in chosen European countries (see above). The label of the situations with a classification symbol is done in accordance with the stated method. That is, the situations that were caused by a lone traffic participant are labelled by the level of seriousness. The traffic conflicts with two or more participants have the level of seriousness 2 or 3 – in the table they are labelled on the place of the 3rd character in this way: 2(3).

One of the above-mentioned conflicts is not wanted guidance of vehicle into the roundabout (see Fig. 2). It shows the course of passage of two heavy vehicles, which enter into the turbo-roundabout. There are no physical separation elements and the lanes are divided only by traffic signs. The vehicle (1) approaches the paved part of the truck apron of the roundabout because of the reason

that the vehicle in the outer lane goes across the traffic signs (2). The vehicle in the inner lane is then forced to stop (3), because the vehicle in the outer lane of the roundabout goes between two lanes (4). This is followed by a gradual start of the vehicle (5) in the inner lane. The vehicle exiting the roundabout still interferes in the inner lane of the roundabout (6). The vehicle in the inner lane leaves the roundabout at the next exit (7). During the measurements at this turbo-roundabout, this traffic conflict was repeated several times, while other road users were also negatively affected. The truck apron of the roundabout shows obvious damage of paved cover from frequent passage and braking of mainly heavy vehicles. The situation described here is a typical construction traffic conflict (i.e. label 6r2(3)-O1S, when it is obvious that the roundabout does not have the necessary geometric parameters (corner radius, etc.). If a lone vehicle passed here incorrectly, the traffic conflict would have a label 2r1-O1S. However, in other cases (or at other roundabouts) it could be an operational traffic conflict, if the geometric parameters of the roundabout are designed correctly, but the wrong passage of the vehicle via the roundabout would be entirely the intention or irresponsibility of the driver.

Tab. 1: Examples of the most common traffic conflicts observed at

turbo-roundabouts.

Type of Traffic Conflict Symbol CRW

[TC/100 veh.]

Not giving way 6n2(3)-O1P 0.74

Not wanted intertwining of vehicles

2p1-O1P

6p2(3)-O1P 0.62

Not wanted change of direction 2k1-O1P

6k2(3)-O1P 0.56

Not wanted guidance of vehicles 2r1-O1S

6r2(3)-O1S 0.44

Shortening the driving path 2s1-O1P

6s2(3)-O1P 0.61

Dangerous approach to the intersection

2a1-O1P

6a2(3)-O1P 0.42

Driving in the opposite direction 6x3-O1P 0.09

Turning of vehicles 2o1-O1P

6o2(3)-O1P 0.39

Not wanted driving on the roundabout

2d1-O1S

6d2(3)-O1S 0.28

Stopping at the roundabout 6z3-O1P 0.11

Fig. 2: Not wanted guidance of vehicles – a subsequent crossing of lanes by the vehicles happens (Olomouc, Czech Republic; GPS: 49.5890953N, 17.3134856E).

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4. Conclusion

The submitted article deals with very specific issues of turbo-roundabouts. However, with a more global view of this issue, we realize the connection to the sustainable transport. An incorrectly designed infrastructure can cause, or intensify the negative consequences of transport on the environment, health of population, etc. Even a small detail, which is not precisely finished, can have immense consequences at the end (e.g. serious accident).

Therefore, the designer of road structures has to consider whether his project of intersection can cause any traffic conflicts mentioned in this article. It is obvious that he/she does not have to conduct such detailed research. However, the conflicts mentioned here are the list of the most frequent conflicts at turbo-roundabouts. On the basis of that, the designer could learn.

Therefore, the article described chosen traffic conflicts that were observed within the scope of the conducted research at turbo-roundabouts in Europe. The sc. construction traffic conflicts (labelled with sign S) were analysed for assessment of effectiveness of geometry of turbo-roundabouts and their construction elements. The impact of physical separation of lane, assessment of the effectiveness of the spike element, the passage of the vehicle over the truck apron or outside truck apron, etc. Further, there were sc. operational traffic conflicts (P), which in the evaluation can be helpful in the analysis of traffic signs. Whether the situation, that was observed, had any connection to the traffic signs, i.e. it was a wrong guidance of the driver into the intersection, ambiguous traffic signs, missing horizontal or vertical traffic signs, etc.

The presented method of video analysis of traffic conflicts and the results stated here confirm certain hypotheses. The analysis of traffic conflicts in road transport is of considerable importance in designing safer roads. It can be a suitable tool for more comprehensive safety inspections. It was further confirmed that turbo-roundabouts, which are considered by many experts to be highly sophisticated and safe solution of intersections, can be a cause of often very serious traffic conflicts, although all technical standards and principles for designing of intersections were met during the design.

Acknowledgements

The works were supported from sources for conceptual development of research, development and innovations for 2020 at the VSB-Technical University of Ostrava which were granted by the Ministry of Education, Youths and Sports of the Czech Republic.

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[10] KOCOUREK, J. and T. PADELEK. Application of the Traffic Conflict Technique in the Czech Republic. In: Smart Cities Symposium. Prague, 2016. ISBN 978-1-5090-1116-2.

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