A PARAMETRIC STUDY ON LATERAL LOAD RESISTANCE ...

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International Journal of Civil Engineering and Technology (IJCIET)

Volume 8, Issue 7, July 2017, pp. 858–875, Article ID: IJCIET_08_07_093

Available online at http://http://iaeme.com/Home/issue/IJCIET?Volume=8&Issue=7

ISSN Print: 0976-6308 and ISSN Online: 0976-6316

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A PARAMETRIC STUDY ON LATERAL LOAD

RESISTANCE OF STEEL CHIMNEYS

M. Pavan Kumar

Assistant Professor of Civil Engineering, SVP Engineering College,

Visakhapatnam, Andhra Pradesh, India

P. Markandeya Raju

Professor of Civil Engineering, MVGR College of Engineering (A),

Vizianagaram, Andhra Pradesh, India

N. Victor Babu

Professor of Civil Engineering, Baba Institute of Technology and Sciences,

Visakhapatnam, Andhra Pradesh, India

K. Roopesh

Post Graduate Student of Structural Engineering,

Baba Institute of Technology and Sciences, Visakhapatnam,

Andhra Pradesh, India

ABSTRACT

This paper presents a computer aided investigation on the seismic and wind effects

on chimneys of different heights in the Indian scenario. Self-supporting steel stacks

(provided as chimneys) of overall height 90m and 110m subjected to wind and seismic

loads are considered in this study. The chimneys are analyzed using STAAD.Pro

software for seismic Zones II, III, IV and V and wind loads of basic wind speeds

39m/sec, 44msec, 49m/sec, and 50m/sec. Maximum shear force and bending moments

developed in the steel stacks along with lateral displacements and mode shapes are

determined and compared to study the structural response of steel stacks.

Keywords: Chimney, Wind Speeds, Seismic Loads, Steel, IS 800 2007, STAAD.Pro;

Cite this Article:M. Pavan Kumar, P. Markandeya Raju, N. Victor Babu and K.

Roopesh, A Parametric Study On Lateral Load Resistance of Steel Chimneys,

International Journal of Civil Engineering and Technology, 8(7), 2017, pp. 858–875.

http://iaeme.com/Home/issue/IJCIET?Volume=8&Issue=7

M. Pavan Kumar, P. Markandeya Raju, N. Victor Babu and K. Roopesh


1. INTRODUCTION

Chimneys are very important industrial structures adopted for the emission of poisonous gases

or smoke at higher altitudes. They are designed as vertical or nearly vertical structures to

ensure smooth flow of gases. Industrial chimneys are commonly referred to as flue gas stacks.

The height of the chimney is based on the ability required to transfer flue gases to the external

environment through stack effect. Chimneys are constructed at least 5m taller than the tallest

building in surrounding area of 150m radius. Different materials such as steel, concrete and

bricks are used for the construction of chimneys.

Steel chimney can be designed as one of the following two types.

(a) Self-supporting steel chimneys: Lateral forces (wind or seismic forces) are transmitted to

the foundation by the cantilever action of the chimney.

(b) Guyed steel chimneys: The mild steel wire ropes or guys are attached to transmit the

lateral forces to ground to ensure the stability of the guyed steel chimney.

Many researchers studied the performance of chimneys under the action of lateral loads.

Par Tranvik et.al. (2007) [1]studied the structural behavior of the 90 m height VEAB steel

chimney in southern Sweden. The authors observed fatigue cracks before nine months of

service. The authors investigated the cause of failure by regularly observing and collecting

measurements of the chimney. The chimney was found to oscillate in both first and second

mode of natural frequency. Raj Kumar et.al. (2011) [2]design self-supported chimneys of

different heights varying from 150m to 250m in two different earthquake zones, Zone 2 and

5.Hard and soft soils were considered for study while varying wind speeds from 33m/s to

55m/s. It was concluded from the study that that stresses induced in zone 5 are almost equal to

stresses induced at minimum wind speed 33m/s. Murali (2012)[3]dealt with the study of three

chimneys of 55m high above ground level designed as per IS 6533 (Part 2) 1989[4]. Wind

load was calculated as per IS: 875 (Part 3) 1987 [5].Three different wind speeds were

considered for the design of chimneys viz., 47m/s, 50m/s and 55m/s respectively. The results

indicated that the thickness of chimney remains same irrespective of the wind speed

considered. Sivakonda Reddy et. al. (2013) [6]studied the effect of wind on 275m tall

chimneys for I and VI wind zones of India. The results indicate that in shell completed

condition, for zone I (i.e. basic wind speed 33m/s) across winds are governing and for highest

wind zone of VI (i.e. basic wind speed 55m/s), along wind loads are governing. The analysis

is carried out using STAAD.Proand MS EXCEL spread sheets. AnilPradeep et.al, (2014)

[7]has analyzed the 60m reinforced concrete chimney. Comparison has been made for wind

and seismic analysis. Seismic analysis is done as per IS 1893(Part 4) 2005 [8] and wind

analysis as per Draft Code CED38 (7892):2013. It is concluded that as zone factor increases,

the magnitude of shear force and bending moment also increases. Rakshit et. al. (2015)

[9]analyzed a cantilever steel chimney as per Indian standards with an objective to explain the

importance of geometrical limitations in the design of cantilever steel chimney. The authors

summarized the analysis and design concepts of chimneys as per Indian code provisions and

incorporated them through finite element analysis. The effect of inspection manhole on the

behavior of cantilever steel chimney was also studied by considering two chimney models,

one with the manhole and other without manhole.Agar et. al. (2015) [10]conducted an

analytical study on the performance based seismic evaluation of industrial chimneys by static

and dynamic analysis. Linear static and dynamic analysis of RC and steel chimneys having

height 65m were performed using SAP2000. The effect of zone on base shear, maximum

lateral displacement, fundamental time period and frequency was studied by comparing the

results of all the zones. Deflection at the free end of chimney is observed to be within the

permissible limits of 0.003h for the both the RC and steel chimney. It was concluded from

this study that steel chimney is more economical in all aspects compared to RC chimney.

A Parametric Study On Lateral Load Resistance of Steel Chimneys


Saran Kumar et.al. (2015) [11]conducted an analytical study on the wind analysis and vortex

shedding effect on steel chimney using computational fluid dynamics. Vortex shedding is

phenomenon that occurs when air or fluid at certain velocity past a cylindrical body forms an

oscillating flow that depends on the size and shape of the body. Reynolds number is used to

predict fluid flow pattern. In this study, five models of chimneys with different heights and

diameters at top and bottom, were designed as per IS 6533 (Part 2) 1989 [4] and wind load are

calculated as per IS: 875 (Part 3) 1987 [5].The study on the vortex shedding effect on

different chimney models reveals that the wind induced vibration in the tall chimneys varies

with respect to height. Chmielewski et. al. (2005) [12]studied the natural frequencies and

natural modes of 250 m high multi-flue industrial RC chimney with the flexibility of soil and

used finite element method for analysis. Also, experimental work to investigate the free

vibration response is carried out by using two geophone sensors and experimental results are

compared with analytical results. The results show that the soil flexibility under the

foundation influences the natural frequency and natural time periods of vibration of the

chimney by considerable margin. Yoganatham et.al. (2013) [13]opined that the analysis and

design of chimneys are normally governed by wind are earthquake load. In this paper modal

analysis of a RCC chimney in a cement factory is carried out using the FEM software package

ANSYS. The effect of changein the dimensions of the chimney on the modal parameters such

as fundamental frequency, displacement etc. are evaluated.

From the review of literature, it is observed that few studies have been conducted on the

wind and seismic performance of Chimneys in the Indian scenario.

2.METHODOLOGY

2.1. General

The basic objective of this study is to investigate the seismic behavior and wind effects on

chimneys in various seismic and wind zones of India. For this study, a hypothetical case of

two Self-supporting steel stack chimneys of height 90m and 110m subjected to wind and

seismic loads are considered as the chimney. The chimneys are considered to be of fixed base

for the purpose of modeling. Methodology of the present study is discussed in the following

sections.

2.2. Geometrical configuration details of steel stack

Two Self-supported steel chimney of heights 90m and 110m are designed as per Indian

Standard codes IS 6533 (Part 1and 2): 1989 [14, 4] in seismic zones II, III, IV, and V for wind

speeds 39m/s, 44m/s, 47m/s, and 50m/s.

The design parameters of the steel stack for 90m height are presented here.

Design Parameters considered

The top diameters of the chimneys are calculated as per IS 6533(Part 1)1989[14]. The

flare heights and the bottom diameters of the chimney are calculated as per IS 6533 (Part 2)

1989[4], Clause 7.2.3and 7.2.4. The relevant calculations are presented below.

Total height of chimney,h = 90m

Flare height of the chimney, hf = (1/3) × 90 = 30m

Top diameter of chimney, D = 3.5m

Flare diameter of chimney, Df = 1.6 × 3.5 = 5.6m

Total height of chimney, h = 110 m

Flare height of the chimney, hf= (1/3) × 110 =40m



Top diameter of chimney, D = 4.5 m

Flare diameter of chimney, Df = 1.6 × 4.5 = 7.5m

Figures 1(a) and 1(b)show the geometry of 90m and 110m chimneys adopted for this study.

Figure 1(a) 90 m Chimney Figure 1(b) 110 m Chimney

Total 8 chimneys are considered for this study. The chimneys are lined with stainless steel

whose unit weight is 78.5kN/m3. The chimney shells are categorized into 9 segments of each

10m along the height for calculation purpose.

General geometric details of the chimney are presented here.

Height - 90m

Diameter of the chimney at bottom 5.6 m

Diameter of the chimney at top 3.5 m

Flare height 30 m

Height of stack 60 m

Height – 110m

Diameter of the chimney at bottom 7.5 m

Diameter of the chimney at top 4.5 m

Flare height 40 m

Height of stack 70 m

2.3. Material Properties

The material properties of the material of the chimney are considered for all calculations as

given below.

Density of steel = 78.5kN/m3

Yield stress of steel = 250kN/m3

Poisson’s ratio=0.3

Strain in elastic range = 0.2%

Modulus of Elasticity (E) of steel = 200000×106N/m2



2.4. Loads acting on the steel chimney

Self-supporting steel chimneys experience various loads in both vertical and lateral

displacements. Important loads that a steel chimney often experiences are wind loads, seismic

loads, and temperature loads apart from self-weight, loads from the attachments, and imposed

loads on service platforms.

The loads considered in this study are Self-weight of chimney, Wind loads and Seismic loads.

2.4.1. Self-weight

Self-weight of chimney is calculated as per IS 875(Part 1): 1987.

2.4.2. Wind loads

Wind effect plays an important role on chimneys as they are tall structures. For self-supported

steel chimneys, wind is considered as major load.

Wind loads are designed as per IS 875(Part 3): 2015.

Design wind speed can be calculated as,

Vz=Vb× k1× k2× k3× k4 as per IS code 875(Part3)2015[15]Clause 6.3

Where,

Vz= Design wind speed at any height z in m/s.

Vb = Basic wind speed

k1 = Probability factor (Risk coefficient)

k2 = Terrain height and structure size factor

k3 = Topography factor

k4= Importance factor for cyclonic region

Design wind pressure,

pz= 0.6 × Vz2 as per IS 875 (Part 3) 2015Clause 5.4

Where,

pz= Design wind pressure in N/m2 at height z

Vz= Design wind velocity in m/s at height z

Wind force,

P = K×pz× A as per IS code 875(Part3) 2015

Where,

P = wind force in N

K = shape factor for chimney (0.7)

A = projected area of chimney in m2

2.4.3. Seismic loads

Seismic load is a major consideration for chimney as it is a natural load. This load is normally

dynamic in nature. Seismic force is estimated as cyclic in nature for short period. For

designing earthquake resistant structures, it is necessary to evaluate the structural response to

ground motion and calculate respective shear force and bending moments. A structure may be

considered serviceable if it is able to fulfil its operational functions for which it was designed.

Earthquake loads are designed as per the code IS 1893(Part 4): 2005.



The fundamental time period of vibration for stack-like structures is,AgE

hWCT

s

tT=

IS 1893(Part 4): 2005. Clause 14.1

Where,

CT = Coefficient depending on slenderness ratio of the structure

Wt= Total weight of the structure including lining weight,

A = Area of cross-section at the base of the structural shell

h = Total height of the structure

Es= Modulus of elasticity of material of the structural shell

g= Acceleration due to gravity

Horizontal seismic force

By using the fundamental time period T, horizontal seismic force Ahcan be obtained.

Ah = (Z/2) × (Sa/g) × (I/R)as per IS code 1893(Part1)2002 Clause 6.4.2.

Where,

Ah= Horizontal seismic coefficient

Z = Zone factor as given in 1S 1893:2005 (Part 1),

I= Importance factor as given in1893:2005 (Part 2)

R=Response reduction factor as given in 1893:2005 (Part 4)

Sa/ g = Spectral acceleration coefficient.

Design shear force and bending moment

Either the simplified method or Dynamic repose spectrum modal analysis method is

recommended for calculating seismic forces developed on this structure.

The shear force V, and the design bending moment M shall be calculated by the following

formulae.

Shear force,

V = Cv×Ah×Wt×Dv

Bending moment,

M = Ah×Wt×h×D

Where,

Cv = Coefficient of shear force depending on slenderness ratio.

Ah= Horizontal seismic coefficient

W= Total weight of structure including lining weight

H = Height of centre of gravity of structure above base

Dv, Dm= Distribution factors for shear and moment

2.5. Load Combinations

The various load combinations considered while designing the steel chimneys in

STAAD.ProV8i are: as per IS 6533 (Part 2) 1989[4].

1.5× (DL+EQ(X))

1.5× (DL+EQ(-X))

1.5×(DL+EQ(Y))



1.5× (DL+EQ(-Y))

1.5× (DL+WL(X))

1.5× (DL+WL(-X))

1.5× (DL+WL(Y))

1.5× (DL+WL(-Y))

Where,

DL = Dead load

EQ(X) = Earthquake load in horizontal direction

EQ(Y) = Earthquake load in vertical direction

WL(X) = Wind load in horizontal direction

WL(Y) = Wind load in vertical direction

2.6. Response Spectrum Method

In order to perform the seismic analysis and design of a structure to be built at a particular

location, the actual time history record is required. However, it is not possible to have such

records at each and every location. Further, the seismic analysis of structures cannot be

carried out simply based on the peak value of the ground acceleration as the response of the

structure depend upon the frequency content of ground motion and its own dynamic

properties. To overcome the above difficulties, earthquake response spectrum is the most

popular method in the seismic analysis of structures. There are computational advantages in

using the response spectrum method of seismic analysis for prediction of displacements and

member forces in structural systems. The method involves the calculation of only the

maximum values of the displacements and member forces in each mode of vibration using

smooth design spectra that are the average of several earthquake motions. Depending upon

the type of resonance, three types of response spectra are identified namely acceleration,

velocity and displacement. If the response of a single degree of freedom system to earthquake

is studied in detail, the response of a system with multi degrees of freedom can found. Mass

having a comparatively shorter natural period T vibrates rapidly, that of longer natural period

T vibrates slowly. The method that is used for the analysis of chimneys is Response spectrum

method. The nodal points that are considered while designing the chimney in STAAD. Pro are

shown.

3. RESULTS AND DISCUSSION

3.1. General

For modeling, the chimney is considered fixed at the bottom and free on the top. Seismic and

wind loads are applied with different combinations and all the displacements, shear force and

bending moments are recorded from the post-processor of STAAD.Pro software. The

behavior of a self-supporting steel chimney in terms of Nodal displacement at various heights,

shear force and bending moment at each segment of a chimney is observed from the results.

3.2. Lateral Displacements

The nodal displacements due to both seismic loads and wind loads for chimneys of heights

90m and 110m have been analyzed for various earthquake zones and wind speeds and the

values obtained are tabulated and plotted in the graph as shown below. All the displacement

values were taken from the post-processor of STAAD.Pro software.



Figure 2 presents the comparison of lateral displacements due to Wind loads for a

chimney of height 90m in 4 wind speeds. From the Figure 2, an increase in percentage of

lateral displacement by 39.87, 60.50 and 72.46 for zones III, IV and V respectively when

compared to zone II are observed. It is also observed that the lateral displacement at the top of

steel stacks for all the seismic zones are in the permissible limit (0.004 × 90=0.36m or

360mm) as per IS 1893(Part 1)2002 Clause 7.11.1.

Figure 2 Lateral displacements due to Seismic loads for a 90 m height chimney in 4 seismic zones

Figure 3 presents the comparison of lateral displacements due to Wind loads for a

chimney of height 90m in 4 wind speeds.

Figure 3 Comparison of lateral displacements due to Wind loads for a chimney of height 90m in 4

basic wind speeds.

79.41

131.98

201.05

288.39

0

50

100

150

200

250

300

0 10 20 30 40 50 60 70 80 90

Dis

pla

cem

ents

(m

m)

Heights of chimney (m)

ZONE II ZONE III ZONE IV ZONE V

387.14

285.484

399.71412.87

345.259

432.94

0

75

150

225

300

375

450

0 10 20 30 40 50 60 70 80 90

Dis

pla

cem

ents

(m

m)

Heights of chimney (m)

39m/s 44m/s 47m/s 50m/s



From the Figure 3, an increase in percentage of lateral displacements by 3.14, 6.23 and

10.58 for basic wind speeds of 44m/sec, 47m/sec, and 50m/sec respectively is observed when

compared to 39m/sec. It is also observed that the lateral displacement at the top of steel stacks

for all the wind speeds are in the permissible limit (h/200=90/200=0.45 or 450mm) as per IS

code IS 6533 (Part 2)1989 Clause 7.4.

Figure 4 presents the comparison of lateral displacements due to Seismic loads for a

chimney of height 110m in 4 zones.

Figure 4 Comparison of lateral displacements due to Seismic loads for a chimney of height 110m in 4

seismic zones


72.64 for zones III, IV and V respectively is observed when compared to zone II.It is also

observed that the lateral displacement at the top of steel stacks for all the seismic zones are in

the permissible limit (0.004×110=0.99m or 440mm) as per IS code IS 1893 (Part 1)2002

clause 7.11.1.

Figure 5 presents comparison of lateral displacements due to Wind loads for a chimney of

height 110m in 4wind speeds.

Figure 5 Comparison of lateral displacements due to Wind loads for a chimney of height 110m in 4

basic wind speeds.

115.88

206.98

278.11

423.55

0

75

150

225

300

375

450

0 10 20 30 40 50 60 70 80 90 100 110

Dis

pa

cem

ents

(m

m)

Heights of Chimney (m)ZONE II ZONE III ZONE IV ZONE IV

232.473

429.85

456.56

486.01

337.024

527.09

0

100

200

300

400

500

0 10 20 30 40 50 60 70 80 90 100 110

Dis

pa

cem

ents

(mm

)

Height of Chimney (m)

39m/s 44m/s 47m/s 50m/s




18.44 for basic wind speeds of 44m/sec, 47m/sec, and 50m/sec respectively is observed when

compared to 39m/sec. It also observed that the lateral displacement at the top of steel stacks

for all the wind speeds are in permissible limit (h/200=110/200=0.55 or 550mm) as per IS

code IS 6533 (Part 2) 1989 clause 7.4.

Figure 6 presents the maximum lateral displacements due to Seismic loads for 90 m and

110 m height chimney in all the 4 seismic zones.

Figure 6 Maximum lateral displacements due to Seismic loads for 90 m and 110 m height chimney in

all the 4 seismic zones

From Figure 6, an increase in percentage of lateral displacements in chimney of 110m

height by 31.46, 36.23, 27.71 and 31.91 for zones II III, IV and V respectively is observed

when compared with that of chimney of 90m height.

Figure 7 presents the comparison of maximum lateral displacements due to wind loads for

a chimney of height 90 and 110m in all the 4 Seismic zones

Figure 7 Comparison of Maximum lateral displacements due to wind loads for a chimney of height 90

and 110m in all the 4 Seismic zones

79

.41 1

31

.98 2

01

.05

28

8.3

9

11

5.8

7

20

6.9

8 27

8.1

1

423.55

0

75

150

225

300

375

450

II III IV V

Dis

pa

cem

ents

(m

m)

Seismic Zones 90m 110m

38

7.1

4

39

9.7

2

41

2.8

7

43

2.9

5

42

9.8

5

45

6.5

6

48

6.0

1

527.09

0

100

200

300

400

500

600

39 44 47 50

Dis

pa

cem

ents

(m

m)

Wind Speeds 90m 110m



From Figure 7, an increase in percentage of lateral displacements in chimney of 110m

height by 9.93, 12.45, 15.04 and 17.86 for basic wind speeds of 39m/sec, 44m/sec, 47m/sec,

and 50m/sec respectively is observed when compared to chimney of 90m height.

3.3. Shear Force and Bending Moment

The variation in shear force and bending moment in various segments of chimneys of 90m

and 110m heights at different earthquake zones and wind speeds are presented in this section.

The results are tabulated and represented in the graphs.

Figure 8 presents the comparison of Shear forces for 90 m height chimney in 4 seismic zones.

Figure 8 Comparison of Shear forces for a chimney of height 90m in 4 zones

From the Figure 8, an increase in percentage of shear force by 38.49, 58.99 and 72.88 for

zones III, IV and V respectively is observed when compared to zone II.

Figure 9 presents the comparison of Bending moments for90 m height chimney in 4 zones.

Figure 9 Comparison of Bending moments for a chimney of height 90m in 4 seismic zones

From the Figure 9, an increase in percentage of bending moment by 38.47, 58.99 and

72.88 for zones III, IV and V respectively is observed when compared to zone II.

Figure 10 presents the comparison of Shear forces for a chimney of height 110m in 4 seismic

zones.

90.6690.66

147.42147.43

221.14

221.14

334.43334.43

0

75

150

225

300

1 2 3 4 5 6 7 8 9

Sh

ear

Fo

rce

(kN

)

Segments of Chimney


2655.531

4317.8

6476.79

9794.824

0

2500

5000

7500

10000

1 2 3 4 5 6 7 8 9Ben

din

g M

om

ent

(kN

_m

)

Segments of Chimney




Figure 10 Comparison of Shear forces for a chimney of height 110m in 4 seismic zones

From Figure 10, an increase in percentage of shear force by 31.09, 34.16 and 78.10 for

zones III, IV and V respectively is observed when compared to zone II.

Figure 11 presents the comparison of Bending moments for a chimney of height 110m in

4 seismic zones.

Figure 11 Comparison of Bending moments for a chimney of height 110m in 4 seismic zones


76.44 is observed for zones III, IV and V respectively when compared to zone II.

Figure 12 presents the comparison of Maximum Shear forces for a chimney of height 90m

and 110m in 4 seismic zones.

118.61

124.86

181.22180.19

189.67

541.69

570.2

0

100

200

300

400

500

600

1 2 3 4 5 6 7 8 9 10 11

Sh

ear

Fo

rce

(kN

)

Segments of chimneyZONE II ZONE III ZONE IV ZONE V

4578.25

4578.25

6954.58 6954.58

20907.3420907.34

0

5000

10000

15000

20000

1 2 3 4 5 6 7 8 9 10 11

Ben

din

g M

om

ent

(kN

m)

Segments of chimney




Figure 12 Comparison of Maximum Shear forces for a chimney of height 90m and 110m in 4 seismic

zones

From the Figure 12, an increase in percentage of maximum shear force for chimney of

110m height by 27.39, 18.65, 14.23, 27.71 and 41.35 for zones II III, IV and V respectively is

observed when compared to chimney of 90m height.

Figure 13 presents the comparison of Maximum Bending Moment for a chimney of height

90m and 110m in 4 seismic zones

Figure 13 Comparison of Maximum Bending Moment for a chimney of height 90m and 110m in 4

zones

From the Figure 13, an increase in percentage of maximum Bending Moment in chimney

of 110m height by 41.99, 35.01, 6.86 and 53.15 for zones II III, IV and V respectively is

observed when compared to chimney of 90m height.

Figure 14 presents the comparison of Shear forces for a chimney of height 90m in 4 wind

speeds.

90

.66 14

7.4

2 22

1.1

4

33

4.4

2

12

4.8

6

18

1.2

2

18

9.6

7

570.2

0

100

200

300

400

500

600

II III IV V

Sh

ear

Fo

rce

(kN

)

Zones 90m 110m

26

55

.53

1

43

17

.8 64

76

.79 97

94

.82

4

45

78

.25

66

44

.73

5

69

54

.58

20907.34

0

3500

7000

10500

14000

17500

21000

II III IV V

Be

nd

ing

Mo

me

nt

(kN

m)

Zones 90m 110m



Figure 14 Comparison of Shear forces for a chimney of height 90m in 4 wind speeds


basic wind speeds of 44m/sec, 47m/sec, and 50m/sec respectively is observed when compared

to 39m/sec.

Figure 15 Comparison of Bending moments for a chimney of height 90m in 4 wind speeds


41.39 for basic wind speeds of 44m/sec, 47m/sec, 50m/sec respectively is observed when

compared to 39m/sec.

Figure 16 presents the comparison of Shear forces for a chimney of height 110m in 4 wind

speeds.

33.22

37.67

43.07

48.8449.15

55.7554.24

64.28

30

40

50

60

1 2 3 4 5 6 7 8 9

Sh

ear

Fo

rce

(kN

)

Segments of chimney

39m/s 44m/s 47m/s 50m/s

2989.98

3390.12

3876.39

4395.604423.23

5017.414881.87

5784.75

2500

3000

3500

4000

4500

5000

5500

6000

1 2 3 4 5 6 7 8 9

Ben

din

g M

om

ent

(kN

m)

Segments of Chimney

39m/s 44m/s 47m/s 50m/s



Figure 16 Comparison of Shear forces for a chimney of height 110m in 4 wind speeds


basic wind speeds of 44m/sec, 47m/sec, and 50m/sec respectively is observed when compared

to 39m/sec.

Figure 17 presents the comparison of Bending moments for a chimney of height 110m in

4 Wind Speeds.

Figure 17 Comparison of Bending moments for a chimney of height 110m in 4 Wind Speeds.


41.39 for basic wind speeds of 44m/sec, 47m/sec and 50m/sec respectively is observed when

compared to 39m/sec.

Figure 18 presents the comparison of Maximum Shear forces for a chimney of height 90m

and 110m in 4 Wind speed.

106.79

138.54

158.00

182.20

25

75

125

175

1 2 3 4 5 6 7 8 9 10 11

Sh

ear

Fo

rce

(kN

)

Segments of Chimney

39m/s 44m/s 47m/s 50m/s

14861.34

15239.07

17380.44

20041.56

2500

7500

12500

17500

22500

1 2 3 4 5 6 7 8 9 10 11

Ben

din

g M

om

ent

(kN

m)

Segments of chimney

39m/s 44m/s 47m/s 50m/s



Figure 18 Comparison of Maximum Shear forces for a chimney of height 90m and 110m in 4 Wind

speed

From the Figure 18, an increase in percentage of maximum shear force in chimney of

110m height by 64.72, 64.74, 64.71, and 64.72 for basic wind speeds 39m/sec, 44m/sec,

47m/sec, and 50m/sec respectively are observed when compared to chimney of 90m height.

Figure 19 presents the comparison of Maximum Bending moments for a chimney of

height 90m and 110m in 4 seismic zones.

Figure 19 Comparison of Maximum Bending moments for a chimney of height 90m and 110m in 4

seismic zones.

From the Figure 19, an increase in percentage of maximum Bending Moment in chimney

of 110m height by 30.26, 71.15, 71.13 and 71.13 for basic wind speeds 39m/sec, 44m/sec,

47m/sec, and 50m/sec respectively is observed when compared to chimney of 90m height.

37

.67

48

.84

55

.75

64

.28

10

6.7

9

13

8.5

4

15

8.0

0 182.20

0

20

40

60

80

100

120

140

160

180

200

39m/sec 44m/sec 47m/sec 50m/sec

She

ar F

orc

e(k

N)

Basic Wind Speed 90m 110m

33

90

.12

43

95

.60

50

17

.41

57

84

.75

14

86

1.3

4

15

23

9.0

7

17

38

0.4

4

20

04

1.5

6

0

5000

10000

15000

20000

25000

39m/sec 44m/sec 47m/sec 50m/sec

Ben

din

g M

om

ent(

kN

m)

Basic Wind Speed 90m 110m



3.4. Response Spectrum for Frequency, Time Periods and Spectral Acceleration

of 90m & 110m Height Chimney

The magnitudes of Frequency, Time periods and spectral accelerations from the response

spectrum analysis (using STAAD.Pro) of chimneys of heights 90m and 110m for various

Seismic zones and basic wind speeds are plotted and discussed in this section.

Figure 20 (a) Comparison of

Frequency for a chimney of

height 90m and 110m

Figure 20 (b) Comparison of

Period for a chimney of height

90 and 110m

Figure 20 (c) Comparison of

spectral acceleration for a

chimney of height 90m and

110m.

From the Figure 20 (a), an increase in percentage of maximum frequency in chimney of

110m height of 24.81 respectively is observed when compared to chimney of 90m height.

From the Figure 20 (b), an increase in percentage of maximum Time period in chimney of

90m height of 16.35 respectively is observed when compared to chimney of 110m height.

From the Figure 20 (c), maximum Spectral acceleration in chimney of 90m height is equal to

that of chimney of 110m height.

4. CONCLUSIONS

From the analytical study presented in this paper, the following are some specific and general

conclusions.

The maximum displacements for both the chimneys are observed for earthquake zone

V.The maximum displacements for both the chimneys are found in areas with higher wind

speed i.e., at 50m/s. There is more impact of wind load on the chimney when compared to

seismic load. The value of shear force becomes constant after the 4th segment for both the

chimneys. The value of bending moment increases with increase in height of segments from

bottom to top and also with increase in seismic zones.The maximum values of shear force and

bending moment shows that as the height of chimney increases the intensity of shear force

and bending moment values at the bottom segment also increases at a higher rate.

2.74

2.06

0

1

1

2

2

3

3

90M 110M

Fre

qu

ency

1.33

1.59

1.2

1.25

1.3

1.35

1.4

1.45

1.5

1.55

1.6

1.65

90M 110M

Tim

e P

eroid

(se

c.)

2.50 2.50

0.0

0.5

1.0

1.5

2.0

2.5

3.0

90M 110MS

pec

tra

l A

ccle

rati

on



REFERENCES

[1] Par Tranvik, Göran Alpsten “Structural Behaviour under Wind loading of a 90 m Steel

Chimney, Wind and Structures, 8(1), pp. 61-78.

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A PARAMETRIC STUDY ON LATERAL LOAD RESISTANCE ...

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