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1 INTRODUCTION The sustainable restoration of Reinforced Concrete (RC) buildings built after World War II in Europe is nowadays an important issue towards a better society. These buildings are characterized by well-known low energy efficiency, living discomfort and by low architectural and urban quality, and are mainly clustered in vast and degraded urban suburbs (Fig.1a).

(a) (b)

Figure 1. a) Aerial view of a typical district build in the 1950-1970. The buildings constructed after World War II are considered to constitute more of the 50% of the total building stock in Europe. b) European seismic hazard map.

More importantly, most of these buildings have already exhausted their design service life

(50 years, NTC2008) and often have significant structural problems, with regards to both static and seismic actions (Kunnath et al., 1995, Masi 2003). As a matter of fact, it is worth noting that these buildings were designed and constructed in absence of any seismic rules (seismic building codes appeared the seventies) or any reference to good seismic-resistant RC construction

Energy efficiency upgrading, architectural restyling and structural retrofit of modern buildings by means of “engineered” double skin façade

F. Feroldi, A. Marini, B. Badiani, G.A. Plizzari, E. Giuriani Department of Civil, Architectural, Environmental and Land Planning Engineering, Brescia, Italy

P. Riva, A. Belleri University of Bergamo, Italy

ABSTRACT: The buildings built after world-war II in the Euro-Mediterranean area are about 50% of the building heritage; their structures are typically made of RC frames with masonry infill walls. After a service life of approximately 50-60 years, they now show structural and energy deficiencies and their maintenance is considered not sustainable. The aim of th is paper is to promote the sustainable renewal and valorization of these residential buildings by adopting double skin façade solutions for structural strengthening, energy efficiency upgrade and architectural renewal. The proposed technique can be considered as a paradigmatic solution which can be referenced for the rehabilitation of degraded RC building, and can be easily adapted to comply with different geographical, climatic and urban contexts, and with different seismic intensity levels. The proposal solution represents a sustainable alternative to the traditional demolition-reconstruction interventions and complete the energy-architectural rehabilitation.

practice, with static loads that were often lower thanFurthermore, durability concepts were not widely diffused at that time and buildings suffered a significant degradation during their service life.deficiencies of these buildings become even more significant, especially in seismic prone areas such as in the south Mediterranean European countriesGreece, Turkey; Fig. 1b).

The RC building stock built after World War II is so vast as toon the need of renewal. Nowadays the restoration of these buildings is usually intended as a reduction of the energy consumption; unlike energy issues, the structural deficiencies are often either not recognized, neglected

Demolition and reconstruction are no longer extensively pursuit for the unbearable environmental load of the production of new construction materials and for the excessive demolition waste produced1; unless one gets a post-intervention building 2011).

2 BACKGROUND The requalification of existing buildings has always been approached by solving episodic, contingent problems exhibited byarchitectural or, more rarely, structural problems. The interventions have been often carried out mainly in emergency situations, without any general planning. The proposed solutions, althouoften innovative, have therefore been limited to solving only part of the problems, without considering the complexity and the interrelation of the building deficiencies

Since the 80s a growing need for urban requalification has been fEuropean Countries started major projects of sustainable requalification of social housingthrough double-skin interventions, that consist in overlaying the existing building with a second technological layer, mainly placed in adhesion energy efficiency and to renovate the building architecturerequalification technique was called “camouflage” and no structural issues was taken into account. Some distinguished out in the Lièvre D’or district at Dreux and in the Rehabsol district at Valence (1995), in Baggesensgade (Copenaghen 1985), and in Vesterbro (Copenaghen 1992).

In Italy the financial incentive program called “Contratti di Quartiere”, introduced in 1997(some “district contracts” in Lombardia: Sant’Eusebio I and II in Cinisello Balsamo, 19982012; Gratosoglio district in Milano, in progresscharacterized by deteriorated buildings and degraded environmentlavished by the Public Administration)by itself to boost a new trend in traditional building restoration and not evchange in urban requalification

From a structural point of viewapproach”, consisting of the local retrofit of the frame joints and members for the strengthened frame to resist the seismic actionsprovided with a brand new structure designed to resi

Figure 2. Structural retrofit techniques“global approach”, with the constructions of new

1 Art. 184, c. 3, letter b, DL 152/06 on Waste management and Decontamination of polluted soils.2 DM 22th October 1997.

that were often lower than the ones now required by current codesFurthermore, durability concepts were not widely diffused at that time and buildings suffered a significant degradation during their service life. As a consequence, the recurrent structural

ldings become even more significant, especially in seismic prone areas Mediterranean European countries (Italy, south France and Spain, Portugal,

The RC building stock built after World War II is so vast as to require an important reflection Nowadays the restoration of these buildings is usually intended as a

reduction of the energy consumption; unlike energy issues, the structural deficiencies are often either not recognized, neglected or ignored.

Demolition and reconstruction are no longer extensively pursuit for the unbearable environmental load of the production of new construction materials and for the excessive

also from an economical point of view they are not convenient, intervention building volume which is twice the original one

he requalification of existing buildings has always been approached by solving episodic, contingent problems exhibited by the building, either referred to particular energy deficiencies, architectural or, more rarely, structural problems. The interventions have been often carried out mainly in emergency situations, without any general planning. The proposed solutions, althouoften innovative, have therefore been limited to solving only part of the problems, without considering the complexity and the interrelation of the building deficiencies (AA. VV., 2006)

a growing need for urban requalification has been felt in Europestarted major projects of sustainable requalification of social housing

skin interventions, that consist in overlaying the existing building with a second technological layer, mainly placed in adhesion to the existing façade, designed to improve energy efficiency and to renovate the building architecture (Malighetti, 2011)requalification technique was called “camouflage” and no structural issues was taken into

Some distinguished examples of sustainable requalification projects are those carried out in the Lièvre D’or district at Dreux and in the Rehabsol district at Valence (1995), in Baggesensgade (Copenaghen 1985), and in Vesterbro (Copenaghen 1992).

incentive program called “Contratti di Quartiere”, introduced in 1997“district contracts” in Lombardia: Sant’Eusebio I and II in Cinisello Balsamo, 1998Gratosoglio district in Milano, in progress) to encourage urban renewal in area

ized by deteriorated buildings and degraded environment (due to financial incentiveed by the Public Administration), was a meaningful experience, although it was not able

by itself to boost a new trend in traditional building restoration and not evalification.

structural point of view, two main approaches are addressed nowadays: the “local the local retrofit of the frame joints and members for the strengthened

seismic actions (Fig. 2a); and the “global approach”, where the building is provided with a brand new structure designed to resist the horizontal loads (Fig. 2

a)

tructural retrofit techniques: a) “local approach”, with local retrofit of the frame joints; b) “global approach”, with the constructions of new seismic-resistance structural elements.

Art. 184, c. 3, letter b, DL 152/06 on Waste management and Decontamination of polluted soils.

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the ones now required by current codes. Furthermore, durability concepts were not widely diffused at that time and buildings suffered a

As a consequence, the recurrent structural ldings become even more significant, especially in seismic prone areas

(Italy, south France and Spain, Portugal,

require an important reflection Nowadays the restoration of these buildings is usually intended as a

reduction of the energy consumption; unlike energy issues, the structural deficiencies are often

Demolition and reconstruction are no longer extensively pursuit for the unbearable environmental load of the production of new construction materials and for the excessive

are not convenient, original one (Micelli,

he requalification of existing buildings has always been approached by solving episodic, the building, either referred to particular energy deficiencies,

architectural or, more rarely, structural problems. The interventions have been often carried out mainly in emergency situations, without any general planning. The proposed solutions, although often innovative, have therefore been limited to solving only part of the problems, without

(AA. VV., 2006). elt in Europe. Some

started major projects of sustainable requalification of social housing skin interventions, that consist in overlaying the existing building with a second

to the existing façade, designed to improve 2011). The resulting

requalification technique was called “camouflage” and no structural issues was taken into examples of sustainable requalification projects are those carried

out in the Lièvre D’or district at Dreux and in the Rehabsol district at Valence (1995), in

incentive program called “Contratti di Quartiere”, introduced in 19972 “district contracts” in Lombardia: Sant’Eusebio I and II in Cinisello Balsamo, 1998-

urban renewal in area to financial incentives

was a meaningful experience, although it was not able by itself to boost a new trend in traditional building restoration and not even a remarkable

two main approaches are addressed nowadays: the “local the local retrofit of the frame joints and members for the strengthened

“global approach”, where the building is st the horizontal loads (Fig. 2b).

b)

“local approach”, with local retrofit of the frame joints; b) al elements.

Art. 184, c. 3, letter b, DL 152/06 on Waste management and Decontamination of polluted soils.

3

Local strengthening techniques, usually consisting in the jacketing of the frame elements and joints with high performance concrete coatings or with FRP wrappings (Martinola et al., 2007, Balsamo et al., 2005), are generally quite expensive as they require demolition of the finishing.

A global intervention, which is based on the construction of external seismic-resistant devices consisting of steel braced frames or RC walls (Marini et al., 2009), is generally the most effective and reliable from the structural point of view (Riva et al., 2010) but it may raise several issues because of the environmental impact and building compatibility that cannot be effectively and systematically solved.

The state of the art shows the lack of a synthesis and integration of structural, functional and energy knowledge, which results in the lack of proposals for coordinated interventions. Recent earthquakes have emphasized the little forethought of these types of interventions: scenes after L’Aquila earthquake, showing broken windows and solar panels, as well as wrecked thermal insulation elements clustered on top of the ruins of many palaces, should be remembered before granting national funds3 for the sole energy efficiency upgrade. This situation highlights how the rehabilitation leading concept of eco-sustainability, environmental quality, renewable energy and energy efficiency should be integrated with the fundamental building structural safety requirement.

3 THE PROPOSAL In this scenario, the main aim of this project is to propose an effective “integrated” solution to promote the sustainable renewal of the vast RC building stock built after World War II. An external “integrated” double casing is proposed and designed to enhance the building energy efficiency, the architectural and urban environment quality as well as its structural safety (Fig. 3). The external structural and technological double casing technique is studied with a special attention to the respect of the minimum environmental impact criteria and minimum rehabilitation cost requirement.

Figure 3. Schematic representation of the proposed external “integrated” adaptive-engineered double skin façade solution, conceived to achieve at the same time architectural remodeling, energy efficiency improvement and structural performance upgrading in the full respect of the minimum environmental impact principles, minimum rehabilitation cost requirement, minimum impairing of the residents.

Reference is made to the double skin façade solutions, used in the past for the sole building

energy retrofitting and architectural renewal. The double skin solution is here conceived as a “exoskeleton” with a double value: on one hand the structure provides the existing buildings with the necessary seismic resistance and its dry installation does not require prolonged phases of construction, on the other hand the external solution guarantees the minimum impact on the inhabitants during the building rehabilitation and allows future functional and formal variations.

Depending on urban planning restrictions, the engineered double skin can be configured in adhesion to the existing building, or as an enlargement of the existing structure on one more

3 Article. 1, com. 344-349 of the Act of 27 December 2006 n. 296 introduced a specific tax benefit (equal to 55% of the cost) for the implementation of interventions aimed at reducing energy consumption, carried out on existing buildings.

sides, thus creating, for example,technique may even allow the construction of new storiespartially balance the upgrade costs

This new technique is proposed as a paradigmatic solcomply with different geographical, climatic and urban contexts, and with different seismic intensity levels.

In order to identify frequent building deficiencies and the requalification needs, typologicalanalysis of the architectural, energetic, structural and

Figure 4. The technical form provides information requalification project criteria.

3.1 A case study

In order to achieve a detailed knowledge of technical forms has been generatedaddressing typological analysis of the building, urban planning parameters, energy

, for example, new living spaces, balconies, solar greenhousesallow the construction of new stories, whose revenues from sale might

partially balance the upgrade costs. is proposed as a paradigmatic solution, that can be easily adapted to

comply with different geographical, climatic and urban contexts, and with different seismic

In order to identify frequent building deficiencies and the requalification needs, typologicalenergetic, structural and urban quality characteristics is necessary.

DESCRIPTION OF THE BUILDING TYPOLOGY

MAXIMUN BUILDING EXPANSION ALLOWED BY THE URBAN

PLANNING RESTRICTIONS

STRUCTURAL PROBLEMS AND TARGET OF STRUCTURAL STRENGTHENING

ENERGY EFFICIENCY DEFICIENCIES AND MAIN TARGET OF ENERGY RENEWAL

Figure 4. The technical form provides information about the building and allow to identify the

In order to achieve a detailed knowledge of the building stock built after World War IIgenerated. The forms are arranged into five different sections

typological analysis of the building, urban planning parameters, energy

Insufficient thermal insulation

4

solar greenhouses. The whose revenues from sale might

ution, that can be easily adapted to comply with different geographical, climatic and urban contexts, and with different seismic

In order to identify frequent building deficiencies and the requalification needs, typological urban quality characteristics is necessary.

DESCRIPTION OF THE BUILDING TYPOLOGY

MAXIMUN BUILDING EXPANSION ALLOWED BY THE URBAN PLANNING RESTRICTIONS

STRUCTURAL PROBLEMS AND TARGET OF STRUCTURAL STRENGTHENING

ENERGY EFFICIENCY DEFICIENCIES AND MAIN TARGET OF ENERGY RENEWAL

identify the

building stock built after World War II, specific five different sections,

typological analysis of the building, urban planning parameters, energy

thermal insulation

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characteristics, structural details and finally any intervention already performed on the existing building (Fig. 4).

Urban planning constraints affect possible models of building volume expansion. The energetic analysis allows to identify the energy requalification needs; the evaluation of static and seismic deficiencies is fundamental to estimate the building seismic vulnerability and to identify possible collapse mechanisms.

In the following a real case-study will be analyzed. The case-study is a typical RC residential public building built in the 1950-1970. The building consists of six stories with a piloti floor at the basement level.

Besides information of the single analyzed building, when the analysis is carried out at the urban level, the data collected allow to create a database containing the synthesis of the typical details of RC buildings; these data are then sorted in a GIS software. Due to the potentialities of GIS, thematic maps can be produced: maps of urban feasibility are obtained by means of the main features of buildings and the standards of the urban context. Joining them with the urban planning restrictions, it will be possible to highlight the most common situations. Furthermore, seismic vulnerability indexes are included in the database and seismic-vulnerability maps can be obtained before earthquake for the case study districts by intersecting seismic hazard and seismic vulnerability data. As an example of these maps, Figure 5a identifies buildings on which the double skin solution can be configured as an enlargement of the existing structure (according to Brescia district standards, if the distance from the property line is more than 5 m, if the distance between the nearest buildings is more than 10 m), Figure 5b identifies buildings on which new stories can be built (if the height of the building is lower than the maximum height allowed in the area). Letters H, M and L mean High, Medium and Low vulnerability.

Figure 5: Results obtained after the typological analysis of some buildings: (a) buildings on which the double skin solution can be configured as an enlargement of the existing structure (squared pattern identifies buildings that satisfy this condition); (b) buildings on which new stories can be built (squared pattern identifies buildings that satisfy this condition). Letters H, M and L mean High, Medium and Low vulnerability.

3.2 Example of engineered integrated double skin: a case study

The above mentioned technical forms are useful tools that should ensure the adoption of the most suitable and cost-optimal solutions to adapt, renew and rehabilitate groups of existing buildings by using an integrated approach. In order to illustrate the effectiveness and the feasibility of the engineered double skin solution, the building analyzed in the previous section is here referenced as an application case study.

The requalification design process starts with the analysis of the original design project in order to achieve a good knowledge of the structural and architectural details. The structure is located in a peripheral district of Brescia (a main city of northern Italy) and was designed before the introduction of seismic building codes; therefore the building lacks any detail of good seismic-resistance construction practice. The building is made of RC frames with sandwich wall panels, RC frames are oriented in a single direction and are characterized by low-ductility structural details. Furthermore, the light-weight RC floors (with light masonry blocks) are made without the RC topping slab and staircase concrete walls are designed for gravity loads only.

The building is even characterized by the absein the so called pilotis configuration earthquake. This configuration is very dangerous from a seismic point of view, because the lateral response of this buildingat the end sections of the columns of the first storquasi-rigid body.

The second step of the analysis focuses onhorizontal loads. Initially, deformation and force capacitywalls). These simplified methods are used to control the results obtained with numerical analyses, such as nelement analysis is carried outexpected, the results show a soft and to provide the existing building according to the proposed engineered structures are proposed and they of braced frames are taken into account: from more traditionframes or reinforced concrete wallssteel’ panels set in a steel frame.

Figure 6. Different types of seismic resistant structures

Figure 7. Example of an enlargement of the existing structure(right side), while on the opposite side facing the street the structure (left side).

The location of the building

nearest buildings represent the main urban planning constraints. constraints entail the possibility to design the double skin as an enlargement of the existing structure only on one side; on the other side, facing the street, the new involucre must be in adhesion to the existing façade (Fig.7).

In order to design the new seismic resistant structure, tentativeassumed. Number and width well as with the position of existing balconies and windows.

The effectiveness of the intervention is strictly related to efficient floor diaphragms, transferperimetral walls. The traditional diaphragms

Max 50 cm

The building is even characterized by the absence of claddings at the ground floor the so called pilotis configuration that can cause a soft first storey mechanism in case of an

. This configuration is very dangerous from a seismic point of view, because the is building is characterized by large rotation ductility request

sections of the columns of the first storey, while the elevation structure behaves like a

of the analysis focuses on the response of the structure subjected to Initially, simplified analytical methods are used in order to estimate

deformation and force capacity of individual structural components (columns and concrete . These simplified methods are used to control the results obtained with

non linear static (pushover) analysis (Calvi, 2008)carried out to estimate the behavior of the building under seismic loads

the results show a soft first storey mechanism. To prevent this collapse mechanism and to provide the existing building with the necessary seismic resistance and structural safety, according to the proposed engineered double skin technique, external seismic

they are designed to be hidden in the new involucreof braced frames are taken into account: from more traditional solutions (

ced concrete walls) to innovative techniques with micro perforated set in a steel frame. In this case, the steel framed structural walls are adopted.

seismic resistant structures proposed for the double skin technique.

an enlargement of the existing structure only on the side facing the green area

(right side), while on the opposite side facing the street the double skin is in adhesion to the existing

building in the lot and the distance from the property lines and from the nearest buildings represent the main urban planning constraints. The urban parameters and constraints entail the possibility to design the double skin as an enlargement of the existing

one side; on the other side, facing the street, the new involucre must be in adhesion to the existing façade (Fig.7).

In order to design the new seismic resistant structure, tentative structural walls are initially assumed. Number and width of these walls are set to comply with architectural restrictions, as well as with the position of existing balconies and windows.

The effectiveness of the intervention is strictly related to the possibility of efficient floor diaphragms, transferring seismic actions from the existing

walls. The traditional diaphragms are made with RC slabs cast

Max 350 cm

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nce of claddings at the ground floor which results mechanism in case of an

. This configuration is very dangerous from a seismic point of view, because the arge rotation ductility request concentrated

structure behaves like a

structure subjected to simplified analytical methods are used in order to estimate

columns and concrete . These simplified methods are used to control the results obtained with more advanced

(Calvi, 2008). Non linear finite under seismic loads; as

To prevent this collapse mechanism the necessary seismic resistance and structural safety, double skin technique, external seismic-resistant

involucre. Different types (with steel braced

micro perforated ‘corten the steel framed structural walls are adopted.

for the double skin technique.

only on the side facing the green area in adhesion to the existing

and the distance from the property lines and from the The urban parameters and

constraints entail the possibility to design the double skin as an enlargement of the existing one side; on the other side, facing the street, the new involucre must be in

structural walls are initially s are set to comply with architectural restrictions, as

the possibility of the formation of eismic actions from the existing building to the

RC slabs cast overlaying the

existing floor extrados. This interventionthe floor finishing and the necessity to relocate the inhabitants during the works. Innovative intrados diaphragms connectedthe residents; since dry solutions are preferred, intrados steel profiles are used

Figure 8. Intrados steel diaphragms.

(a) Figure 9. Schematic representation of the requalification proposal: a) 1970 RC building before the renewal; b) adoption of a double external casing integrating energy effiseismic-resistant structures, and all the architectural finishing.

Special attention is devoted

involucre skin. A dissipative connection linking the new casing and the existing structure is still under study (Christopoulos et allocalizing the possible damage caused by an earthquake, so that postworks are limited to the replacement of atherefore very cost and time effective. This solution is therefore respectful of theand minimum cost criteria.

The evaluation of the energy efficiency of the case studyenergy deficiencies and to define the target ois aimed at solving main building deficiencies, such as thermal bridges and insufficient thermal insulation of external walls, in order to guarantee thermal comfort and to the primary energy use for heating and acoustic insulation panels are placed on external existing walls. Building simulation using

. This intervention is not sustainable because it requires the demolition of and the necessity to relocate the inhabitants during the works. Innovative connected to the floor ceiling are designed for the minimum impairment of

the residents; since dry solutions are preferred, intrados steel profiles are used (Fi

ntrados steel diaphragms.

(b)

Schematic representation of the requalification proposal: a) 1970 RC building before the renewal; b) adoption of a double external casing integrating energy efficiency requalification devices with

structures, and all the architectural finishing.

devoted to the connection between the existing structure and the new connection linking the new casing and the existing structure is still

et al., 2006). The idea is to develop a special connector capable of the possible damage caused by an earthquake, so that post-earthquake limited to the replacement of a few damaged connection devices only, and will be ry cost and time effective. This solution is therefore respectful of the

he evaluation of the energy efficiency of the case study building allows identifyingenergy deficiencies and to define the target of the intervention. The energy efficiency upgrading

main building deficiencies, such as thermal bridges and insufficient thermal insulation of external walls, in order to guarantee thermal comfort and to

for heating and the resulting CO2 emissions. To this end, new thermal and acoustic insulation panels are placed on external existing walls. Building simulation using

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because it requires the demolition of and the necessity to relocate the inhabitants during the works. Innovative

to the floor ceiling are designed for the minimum impairment of (Fig. 8).

Schematic representation of the requalification proposal: a) 1970 RC building before the ciency requalification devices with

to the connection between the existing structure and the new connection linking the new casing and the existing structure is still

The idea is to develop a special connector capable of earthquake repairing

few damaged connection devices only, and will be ry cost and time effective. This solution is therefore respectful of the sustainability

identifying the main he energy efficiency upgrading

main building deficiencies, such as thermal bridges and insufficient thermal insulation of external walls, in order to guarantee thermal comfort and to reduce both

To this end, new thermal and acoustic insulation panels are placed on external existing walls. Building simulation using

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thermal software in static conditions allowed to measure the energy consumption reduction after the intervention (a result is a decrease in the consumption of primary energy by up to 80%).

The new involucre also allows functional and formal variations of the building architecture: where the double skin can be an enlargement of the existing structure, new spaces are added to the apartments for additional rooms, solar greenhouses, winter gardens or terraces.

Restyling improves human health and well-being. The society benefits from the new aesthetics of the buildings and the urban district, and so do the residents, whose awareness of living in a structurally safe and fully efficient building, increases personal and social well-being.

4 CONCLUDING REMARKS The objective of this paper is to promote the sustainable renewal and rehabilitation of RC buildings built after World War II by developing an effective integrated solution to provide a versatile response to all the requalification needs, thus overcoming the traditional “episodic” and “case-by-case” intervention approach. This innovative technique is proposed as a paradigmatic solution, that can be adopted or referenced for the rehabilitation of degraded RC building stocks. Emphasis is made to the need for structural rehabilitation of these buildings, which is often neglected in the renewal interventions and sustainability concept is here extended to structural safety for preservation of human life.

The external engineered double skin must be developed in the respect of the minimum environmental impact principles, minimum rehabilitation cost requirement and entails minimum impairing of the residents during the renovation works. The strategy is also aimed at maximizing the living environment quality, thus the health and wellbeing of the inhabitants. The proposed solution can be regarded as an efficient alternative to the existing building demolition and reconstruction. Furthermore it is an alternative to the upgrading of the solely architectural an energetic performances, because an integrated approach allows a significant increment of the building service life, whereas interventions limited to energy efficiency upgrading do not alter the building service life.

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Reinforced Concrete Buildings - Part I: Seismic Evaluation of Existing Construction. Structural Journal. Vol:92. Iss.3. Pages:343-354.

Malighetti L.E. 2011. Recupero edilizio. Strategie per il riuso e tecnologie costruttive. Milano. Il Sole24Ore.

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Martinola G, Meda A, Plizzari G., and Rinaldi Z. 2007. An application of high performance fiber reinforced cementitious composites for R/C beams strengthening. FRAMCOS 6. Catania (Italy). 18-21 June 2007.

Masi A. 2003. Seismic Vulnerability Assessment of Gravity Load Designed R/C Frames. Bulletin of Earthquake Engineering. Volume 1, Number 3, 371-395.

Micelli E. 2011. La gestione dei piani urbanistici. Venezia. Marsilio. NTC2008 -"Norme tecniche per le costruzioni" D.M. 14 Gennaio 2008 Riva P., Perani E., Belleri A. 2010. External R.C. Structural Walls for the Repair of Earthquake

Damaged Buildings. Sustainable Development Strategies for Constructions in Europe and China, Rome 19-20 April 2010.

Christopoulos C., Filiatrault A. 2006. Principles of Passive Supplemental Damping and Seismic Isolation. Pavia. IUSS Press.