The effects of reinforcement corrosion need to be included in the assessment of existing Reinforc... more The effects of reinforcement corrosion need to be included in the assessment of existing Reinforced Concrete structures for a reliable evaluation of the structural performances over time and a correct choice of the renovation strategy. The DEMSA protocol proposes straightforward tools available to professional engineers, enabling the calibration of equivalent damage parameters able to describe corrosion effects starting from environmental easy-measurable conditions. Guidance to implement the equivalent damage parameters describing corrosion effects at a sectional level in the structural analyses is provided. Then, a simplified approach to model the corrosion attack distribution along the bar length is proposed. Finally, nonlinear static analyses are carried out on reference RC frames subjected to different corrosion patterns by adopting fiber modeling technique, to show how the equivalent damage parameters allow detecting the impact of corrosion effects on the structural performances, in terms of internal actions distribution, reduction of stiffness, strength, and ductility.
The effects of deterioration strongly impact the expected future service life and the structural ... more The effects of deterioration strongly impact the expected future service life and the structural performances of existing reinforced concrete structures. Currently, straightforward methodologies are required to include such effects in the assessment and renovation of the RC buildings’ heritage. A simplified protocol enabling the detection, evaluation, and modelling of corrosion effects is presented in this paper. The protocol provides the guidance for the design and management of the on-site diagnostic campaign, aimed at identifying a possible corrosion risk scenario. Then, equivalent damage parameters describing corrosion effects in the structural models can be calibrated. Structural performances over time can be assessed to predict the structural residual life, maintenance management criteria and timing, and major indications on the feasibility of the retrofit intervention, or the unavoidable need of demolition. The application of the proposed protocol to some case studies emphasi...
World Conference on Timber Engineering (WCTE 2023)
The ambitious target of decarbonization requires a deep transformation of the construction sector... more The ambitious target of decarbonization requires a deep transformation of the construction sector and a systematic renovation of the existing building stock. Such a transition requires the adoption of new technologies conceived with a Life Cycle Thinking approach and implementing digital tools, maximizing performances, while enabling reduction of impacts and costs along the building life cycle. In the paper, a wooden construction technology for the deep renovation of existing buildings is presented. The solution is prefabricated off-site, made of a renewable bio-based material, and adopts innovative dry, standardized connections, enabling concentrating damage in case of earthquakes. The system is applied from the outside, without relocating inhabitants, that might otherwise hinder the renovation. An additional CLT engineered shell, coupled with an optimized thermal layer and new plants along the building perimeters, allow the combined energy and structural upgrade of the building. Finally, specific sensors are added for the continuous monitoring of structural health and environmental parameters. The proposed solution was developed within an industrial project integrating academic research and industrial leading-edge technologies and was applied to a typical post-WWII masonry building.
The decarbonization of the construction sector, which is one of the most impactful sectors worldw... more The decarbonization of the construction sector, which is one of the most impactful sectors worldwide, requires a significant paradigm shift from a linear economy to a circular, future-proofed and sustainable economy. In this transition, the role of designers and structural engineers becomes pivotal, and new design objectives and principles inspired by Life Cycle Thinking (LCT) should be defined and included from the early stages of the design process to allow for a truly sustainable renovation of the built environment. In this paper, an overview of LCT-based objectives and principles is provided, critically analyzing the current state of the art of sustainability and circularity in the construction sector. The effectiveness of applying such design principles from the early stages of the design of retrofit interventions is then demonstrated with reference to a case study building. Four seismic retrofit alternatives made of timber, steel and concrete, conceived according to either LCT...
Given the current climate emergency and the ambitious targets of carbon emissions reduction, retr... more Given the current climate emergency and the ambitious targets of carbon emissions reduction, retrofitting strategies on existing buildings typically include reducing energy demand, decarbonising the power supply, and addressing embodied carbon stored in materials. This latter point redefines the role of engineers in the transitions towards a sustainable construction sector, being they responsible for designing low impact, sustainable and carbon neutral solutions. A Life Cycle Structural Engineering (LCSE) approach, inspired by the principles of Life Cycle Thinking (LCT), should thus be adopted for the sustainable renovation of existing buildings. Only recently have pioneering approaches been proposed, tackling multifaceted buildings’ needs, such as those related to energy consumption as well as seismic safety, but often disregarding LCT principles. This study presents a redefinition of the concept of LCSE for sustainable construction and a comprehensive review of available methods a...
The paper deals with the development of an innovative Portland-free lightweight structural plaste... more The paper deals with the development of an innovative Portland-free lightweight structural plaster to improve the seismic performance and the energy efficiency of poor quality stone masonry buildings. In particular, one-part alkali-activated slag-based mortars were manufactured with different lightweight glass aggregate contents to be mechanically compatible with historic stone walls (28-day compressive strength up to 8 MPa) and to serve as a thermo-insulating layer (specific mass lower than 1000 kg/m 3). Results indicate that the Portland-free alkali activated-based plaster manufactured with expanded glass aggregates and air entraining agent is able to provide a 28-day compressive strength equal to 8 MPa and a thermal conductivity of 0.35 W/mK due to density close to 700 kg/m 3. Moreover, by using methylcellulose (MC), modified starch (MS), polypropylene fibers, shrinkage reducing admixture (SRA) and silane-based surface treatment, it is possible to ensure an excellent adhesion to the substrate, the absence of micro-cracks and detachments and a very low water absorption coefficient. KEYWORDS Alkali-activated slag; Expanded glass; Glass mesh; Reinforced plaster; Seismic improvement; Energy upgrade. details of the walls, quality of the materials and their interaction. Poor quality masonry typologies may fail for the onset of local failure mechanisms, such as local detachment and buckling of the masonry leaves, substantially reducing the compressive, shear and flexural strength of the wall [16]. As for the seismic behavior, poor quality of the masonry, particularly in the case of three leaf walls, may dramatically anticipate the failure of the wall, which may be triggered by the out-of-plane IP20-0
Earthquake Engineering & Structural Dynamics, 2017
Recent earthquakes in Italy (L'Aquila 2009 and Emilia 2012) highlighted the vulnerability of prec... more Recent earthquakes in Italy (L'Aquila 2009 and Emilia 2012) highlighted the vulnerability of precast cladding panels, typically associated with a connection system not designed to account for displacement and rotation compatibility between the panels and the supporting structure. Experimental investigations were carried out in the past to investigate the in-plane performance of cladding panels and design recommendations have been made accordingly; however, in the case of out-of-plane seismic loads, the load demand is commonly evaluated in the design practice by means of formulations for non-structural components. This paper summarises the results obtained from parametric analyses conducted to estimate the out-of-plane load demand in column-to-column cladding panels typical of one-storey commercial and industrial buildings. Empirical equations suitable for both new and existing panels are proposed and compared with the design equations given in Eurocode 8 and ASCE 7. The paper also considers the effects of the development of plastic hinges at the column base and of the roof flexibility on the load demand in panel-to-column connections. The roof flexibility may generate the torsion of the panels, consequently an analytical procedure to account for such effects is proposed. Finally, general design recommendations are made.
European Journal of Environmental and Civil Engineering, 2017
In this paper, an integrated approach targeting sustainability, safety, and resilience is envisio... more In this paper, an integrated approach targeting sustainability, safety, and resilience is envisioned for the renovation of the post-World War II RC buildings clustered in urban outskirts. The solution stems as an enhancement of the widespread camouflage practice, which targets energy efficiency and architectural restyling by complementing the building with a technological double skin, self-supported on an independent exoskeleton. Based on this integrated approach, the exoskeleton can be further engineered to also enable structural safety and resilience. Life cycle thinking is addressed to re-conceive traditional structural design approaches, guaranteeing safety, while minimizing costs and environmental impacts over the building life cycle. Accurate selection of materials and dry technologies enables adaptability, reparability and maintenance, and total recyclability/reuse at end-of-life. The intervention is carried out from outside, avoiding relocation of the inhabitants and possible building downtime. The paper introduces a possible framework for engineers, technologists, and architects to design new holistic renovation interventions, for which innovative solution sets are required. Possible structural techniques to be coupled with energy refurbishment are proposed. As a proof of concept, the envisaged holistic renovation strategy is applied to a reference building, and benefits entailed in combining structural safety measures within an integrated intervention are commented.
Abstract Failure and deterioration of structural interventions on masonry buildings demonstrated ... more Abstract Failure and deterioration of structural interventions on masonry buildings demonstrated the need for compatible repairs. Mechanical, chemical, transport properties and density of Portland Cement concrete are poorly compatible with lime mortar masonry structures. Several natural lime composites are developed in this study for compatible Historical Heritage rehabilitation. Two relevant interventions with different strength/density requirements are considered: masonry vault filling and wooden floor non-structural overlay. Density minimization is attained with various lightweight aggregate (LWA) types/contents; different LWAs in one same mortar are also employed. Composites’ density, strength, stiffness, cost, and carbon footprint are compared; the influence of different factors is discussed.
The seismic retrofit of the existing building heritage represents an urgent issue to be faced and... more The seismic retrofit of the existing building heritage represents an urgent issue to be faced and innovative solutions which allow to overcome renovation barriers are needed. In this scenario, pin-supported (PS) walls represent an eligible solution, enabling linearization of the deformation of the frame along its height and inhibiting soft storey collapse mechanisms. The PS wall can be connected to the existing building from outside, thereby avoiding disruption to occupants or their relocation, which are acknowledged as the main barriers to the renovation nowadays. Suitability of PS wall solutions in the seismic retrofit of the existing building stock has been investigated herein, particularly in the case of existing reinforced concrete (RC) buildings, preliminarily focusing on 2D RC frames. The paper shows the weaknesses and strengths of the PS wall solution in relation to the specific features of the considered buildings. An analytical closed-form formulation is proposed and appli...
A growing attention has been paid to the deep renovation of RC buildings, particularly focusing o... more A growing attention has been paid to the deep renovation of RC buildings, particularly focusing on their structural vulnerability and on the development of retrofit strategies; however, the issue of the in-plane diaphragm action and the capacity of existing floors has rarely been addressed. Although floor capacity does not seem critical for the seismic capacity of existing structures, commonly affected by greater vulnerabilities, it may become critical when an additional lateral force resisting system is introduced. This paper investigates the in-plane capacity of beam and hollow-clay-block floor system, typical of the European post-WWII RC buildings. Considering the diaphragm action as associated with an in-plane tied-arch mechanism developing within the floor thickness, the main failure mechanisms are discussed, and some simplified equations are provided to preliminary estimate the maximum capacity of floors. Experimental and numerical analyses are than carried out to validate the simplified analytical model. The relevant influence of possible staircase openings on the in-plane load paths and on diaphragm flexibility and capacity are also considered. Finally, the influence of the floor capacity on the seismic vulnerability assessment and in the conceptual design of a seismic retrofit intervention is discussed. This preliminary study shows that only some of the beam-and-block floor systems have a reliable in-plane capacity, while other typologies cannot serve as floor diaphragms. When the diaphragm action can be relied upon, the diaphragms often exhibit a fairly stiff behaviour up to a brittle failure, which is commonly associated with the ultimate capacity at the tied-arch supports.
The effects of reinforcement corrosion need to be included in the assessment of existing Reinforc... more The effects of reinforcement corrosion need to be included in the assessment of existing Reinforced Concrete structures for a reliable evaluation of the structural performances over time and a correct choice of the renovation strategy. The DEMSA protocol proposes straightforward tools available to professional engineers, enabling the calibration of equivalent damage parameters able to describe corrosion effects starting from environmental easy-measurable conditions. Guidance to implement the equivalent damage parameters describing corrosion effects at a sectional level in the structural analyses is provided. Then, a simplified approach to model the corrosion attack distribution along the bar length is proposed. Finally, nonlinear static analyses are carried out on reference RC frames subjected to different corrosion patterns by adopting fiber modeling technique, to show how the equivalent damage parameters allow detecting the impact of corrosion effects on the structural performances, in terms of internal actions distribution, reduction of stiffness, strength, and ductility.
The effects of deterioration strongly impact the expected future service life and the structural ... more The effects of deterioration strongly impact the expected future service life and the structural performances of existing reinforced concrete structures. Currently, straightforward methodologies are required to include such effects in the assessment and renovation of the RC buildings’ heritage. A simplified protocol enabling the detection, evaluation, and modelling of corrosion effects is presented in this paper. The protocol provides the guidance for the design and management of the on-site diagnostic campaign, aimed at identifying a possible corrosion risk scenario. Then, equivalent damage parameters describing corrosion effects in the structural models can be calibrated. Structural performances over time can be assessed to predict the structural residual life, maintenance management criteria and timing, and major indications on the feasibility of the retrofit intervention, or the unavoidable need of demolition. The application of the proposed protocol to some case studies emphasi...
World Conference on Timber Engineering (WCTE 2023)
The ambitious target of decarbonization requires a deep transformation of the construction sector... more The ambitious target of decarbonization requires a deep transformation of the construction sector and a systematic renovation of the existing building stock. Such a transition requires the adoption of new technologies conceived with a Life Cycle Thinking approach and implementing digital tools, maximizing performances, while enabling reduction of impacts and costs along the building life cycle. In the paper, a wooden construction technology for the deep renovation of existing buildings is presented. The solution is prefabricated off-site, made of a renewable bio-based material, and adopts innovative dry, standardized connections, enabling concentrating damage in case of earthquakes. The system is applied from the outside, without relocating inhabitants, that might otherwise hinder the renovation. An additional CLT engineered shell, coupled with an optimized thermal layer and new plants along the building perimeters, allow the combined energy and structural upgrade of the building. Finally, specific sensors are added for the continuous monitoring of structural health and environmental parameters. The proposed solution was developed within an industrial project integrating academic research and industrial leading-edge technologies and was applied to a typical post-WWII masonry building.
The decarbonization of the construction sector, which is one of the most impactful sectors worldw... more The decarbonization of the construction sector, which is one of the most impactful sectors worldwide, requires a significant paradigm shift from a linear economy to a circular, future-proofed and sustainable economy. In this transition, the role of designers and structural engineers becomes pivotal, and new design objectives and principles inspired by Life Cycle Thinking (LCT) should be defined and included from the early stages of the design process to allow for a truly sustainable renovation of the built environment. In this paper, an overview of LCT-based objectives and principles is provided, critically analyzing the current state of the art of sustainability and circularity in the construction sector. The effectiveness of applying such design principles from the early stages of the design of retrofit interventions is then demonstrated with reference to a case study building. Four seismic retrofit alternatives made of timber, steel and concrete, conceived according to either LCT...
Given the current climate emergency and the ambitious targets of carbon emissions reduction, retr... more Given the current climate emergency and the ambitious targets of carbon emissions reduction, retrofitting strategies on existing buildings typically include reducing energy demand, decarbonising the power supply, and addressing embodied carbon stored in materials. This latter point redefines the role of engineers in the transitions towards a sustainable construction sector, being they responsible for designing low impact, sustainable and carbon neutral solutions. A Life Cycle Structural Engineering (LCSE) approach, inspired by the principles of Life Cycle Thinking (LCT), should thus be adopted for the sustainable renovation of existing buildings. Only recently have pioneering approaches been proposed, tackling multifaceted buildings’ needs, such as those related to energy consumption as well as seismic safety, but often disregarding LCT principles. This study presents a redefinition of the concept of LCSE for sustainable construction and a comprehensive review of available methods a...
The paper deals with the development of an innovative Portland-free lightweight structural plaste... more The paper deals with the development of an innovative Portland-free lightweight structural plaster to improve the seismic performance and the energy efficiency of poor quality stone masonry buildings. In particular, one-part alkali-activated slag-based mortars were manufactured with different lightweight glass aggregate contents to be mechanically compatible with historic stone walls (28-day compressive strength up to 8 MPa) and to serve as a thermo-insulating layer (specific mass lower than 1000 kg/m 3). Results indicate that the Portland-free alkali activated-based plaster manufactured with expanded glass aggregates and air entraining agent is able to provide a 28-day compressive strength equal to 8 MPa and a thermal conductivity of 0.35 W/mK due to density close to 700 kg/m 3. Moreover, by using methylcellulose (MC), modified starch (MS), polypropylene fibers, shrinkage reducing admixture (SRA) and silane-based surface treatment, it is possible to ensure an excellent adhesion to the substrate, the absence of micro-cracks and detachments and a very low water absorption coefficient. KEYWORDS Alkali-activated slag; Expanded glass; Glass mesh; Reinforced plaster; Seismic improvement; Energy upgrade. details of the walls, quality of the materials and their interaction. Poor quality masonry typologies may fail for the onset of local failure mechanisms, such as local detachment and buckling of the masonry leaves, substantially reducing the compressive, shear and flexural strength of the wall [16]. As for the seismic behavior, poor quality of the masonry, particularly in the case of three leaf walls, may dramatically anticipate the failure of the wall, which may be triggered by the out-of-plane IP20-0
Earthquake Engineering & Structural Dynamics, 2017
Recent earthquakes in Italy (L'Aquila 2009 and Emilia 2012) highlighted the vulnerability of prec... more Recent earthquakes in Italy (L'Aquila 2009 and Emilia 2012) highlighted the vulnerability of precast cladding panels, typically associated with a connection system not designed to account for displacement and rotation compatibility between the panels and the supporting structure. Experimental investigations were carried out in the past to investigate the in-plane performance of cladding panels and design recommendations have been made accordingly; however, in the case of out-of-plane seismic loads, the load demand is commonly evaluated in the design practice by means of formulations for non-structural components. This paper summarises the results obtained from parametric analyses conducted to estimate the out-of-plane load demand in column-to-column cladding panels typical of one-storey commercial and industrial buildings. Empirical equations suitable for both new and existing panels are proposed and compared with the design equations given in Eurocode 8 and ASCE 7. The paper also considers the effects of the development of plastic hinges at the column base and of the roof flexibility on the load demand in panel-to-column connections. The roof flexibility may generate the torsion of the panels, consequently an analytical procedure to account for such effects is proposed. Finally, general design recommendations are made.
European Journal of Environmental and Civil Engineering, 2017
In this paper, an integrated approach targeting sustainability, safety, and resilience is envisio... more In this paper, an integrated approach targeting sustainability, safety, and resilience is envisioned for the renovation of the post-World War II RC buildings clustered in urban outskirts. The solution stems as an enhancement of the widespread camouflage practice, which targets energy efficiency and architectural restyling by complementing the building with a technological double skin, self-supported on an independent exoskeleton. Based on this integrated approach, the exoskeleton can be further engineered to also enable structural safety and resilience. Life cycle thinking is addressed to re-conceive traditional structural design approaches, guaranteeing safety, while minimizing costs and environmental impacts over the building life cycle. Accurate selection of materials and dry technologies enables adaptability, reparability and maintenance, and total recyclability/reuse at end-of-life. The intervention is carried out from outside, avoiding relocation of the inhabitants and possible building downtime. The paper introduces a possible framework for engineers, technologists, and architects to design new holistic renovation interventions, for which innovative solution sets are required. Possible structural techniques to be coupled with energy refurbishment are proposed. As a proof of concept, the envisaged holistic renovation strategy is applied to a reference building, and benefits entailed in combining structural safety measures within an integrated intervention are commented.
Abstract Failure and deterioration of structural interventions on masonry buildings demonstrated ... more Abstract Failure and deterioration of structural interventions on masonry buildings demonstrated the need for compatible repairs. Mechanical, chemical, transport properties and density of Portland Cement concrete are poorly compatible with lime mortar masonry structures. Several natural lime composites are developed in this study for compatible Historical Heritage rehabilitation. Two relevant interventions with different strength/density requirements are considered: masonry vault filling and wooden floor non-structural overlay. Density minimization is attained with various lightweight aggregate (LWA) types/contents; different LWAs in one same mortar are also employed. Composites’ density, strength, stiffness, cost, and carbon footprint are compared; the influence of different factors is discussed.
The seismic retrofit of the existing building heritage represents an urgent issue to be faced and... more The seismic retrofit of the existing building heritage represents an urgent issue to be faced and innovative solutions which allow to overcome renovation barriers are needed. In this scenario, pin-supported (PS) walls represent an eligible solution, enabling linearization of the deformation of the frame along its height and inhibiting soft storey collapse mechanisms. The PS wall can be connected to the existing building from outside, thereby avoiding disruption to occupants or their relocation, which are acknowledged as the main barriers to the renovation nowadays. Suitability of PS wall solutions in the seismic retrofit of the existing building stock has been investigated herein, particularly in the case of existing reinforced concrete (RC) buildings, preliminarily focusing on 2D RC frames. The paper shows the weaknesses and strengths of the PS wall solution in relation to the specific features of the considered buildings. An analytical closed-form formulation is proposed and appli...
A growing attention has been paid to the deep renovation of RC buildings, particularly focusing o... more A growing attention has been paid to the deep renovation of RC buildings, particularly focusing on their structural vulnerability and on the development of retrofit strategies; however, the issue of the in-plane diaphragm action and the capacity of existing floors has rarely been addressed. Although floor capacity does not seem critical for the seismic capacity of existing structures, commonly affected by greater vulnerabilities, it may become critical when an additional lateral force resisting system is introduced. This paper investigates the in-plane capacity of beam and hollow-clay-block floor system, typical of the European post-WWII RC buildings. Considering the diaphragm action as associated with an in-plane tied-arch mechanism developing within the floor thickness, the main failure mechanisms are discussed, and some simplified equations are provided to preliminary estimate the maximum capacity of floors. Experimental and numerical analyses are than carried out to validate the simplified analytical model. The relevant influence of possible staircase openings on the in-plane load paths and on diaphragm flexibility and capacity are also considered. Finally, the influence of the floor capacity on the seismic vulnerability assessment and in the conceptual design of a seismic retrofit intervention is discussed. This preliminary study shows that only some of the beam-and-block floor systems have a reliable in-plane capacity, while other typologies cannot serve as floor diaphragms. When the diaphragm action can be relied upon, the diaphragms often exhibit a fairly stiff behaviour up to a brittle failure, which is commonly associated with the ultimate capacity at the tied-arch supports.
The refurbishment of the existing building stock is nowadays becoming a priority in order to meet... more The refurbishment of the existing building stock is nowadays becoming a priority in order to meet energy-saving and emission-control international targets and to foster safety and resilience of European communities. A new research recently introduced the concept of holistic seismic, energy, and architectural renovation of existing buildings targeting resilience, safety, and sustainability. Integrated retrofitting techniques have been proposed, and a new structural design procedure has been studied rethinking existing approaches by including sustainability principles. With reference to post-WWII RC buildings, which are often mid-rise isolated buildings located at the city outskirts, additional exoskeletons implementing the technologies and devices for an integrated upgrade have been proposed. Exoskeletons are entirely built from outside, thus avoiding the temporary dismissal of the buildings and the relocation of the inhabitants. Both ‘shear wall’ or ‘shell’ solutions, either dissipative or over-resistant, can be envisioned for structural retrofitting. In the first solution, shear walls can be integrated in the new exoskeleton, whereas energy efficiency upgrading is guaranteed by the envelope, thus the two structure-energy systems work in parallel. In the ‘shell’ solution, the building envelope has both energy and structural functions. In this paper, both over-resistant and adaptive diagrids are introduced for the holistic refurbishment of existing buildings. Over resistant diagrids are conceived for the seismic upgrade of those buildings having stiff masonry infill walls and staircase walls, for which dissipative solutions may be ineffective unless massive preliminary interventions are carried out to downgrade the existing building initial stiffness. Adaptive diagrids are conceived as over resistant ‘shell' structures to avoid any damage at the operational limit state, while dissipation is triggered through dissipative rigid-plastic supports to reduce shear at the grid foundations at the life safety limit state. Selection of materials and technologies, enabling maximum adaptability, reparability and maintenance, and total demountability-recyclability/reuse at end-of-life is also discussed.
The reinforced concrete constructions built after World War II represent almost half of the Europ... more The reinforced concrete constructions built after World War II represent almost half of the European building stock. Such buildings are characterized by low energy efficiency, living discomfort and may be inherently vulnerable to seismic actions, having been designed before the enforcement of modern building codes. A global integrated intervention for the sustainable restoration of the considered building stock is proposed in this paper. The conceived approach overcomes the shortcomings of the traditional renewal practice, targeting uncoupled solution of single deficiencies. The solution also stems as an enhancement of past pioneering techniques, such as the double skin, focusing on architectural restyling and energy efficiency upgrade. In the proposed approach energy efficiency and structural upgrading measures are coupled, and the exoskeleton is complemented with ad-hoc systems and devices to increase structural safety and seismic resilience. The intervention is carried out from the outside, with reduced impairment of the inhabitants and building downtime. Unlike traditional energy efficiency interventions, the structural upgrade entails a series of co-benefits: it allows lengthening the building service life, thus representing a viable and more sustainable alternative to the building demolition and reconstruction practice; it increases seismic resilience at district level, reduces life cycle costs and minimizes environmental impact over the building life cycle. Despite the research work be multidisciplinary, in this paper emphasis is made on the sole structural issues. The exoskeleton conceptual design is discussed and both over-resistant and dissipative solutions are proposed. Main principles of performance based design are presented, which allow minimizing the damage on the existing building. Finally, the case study of a typical residential building is presented, in which the possible use of the engineered double skin is proposed as an alternative to the basic double skin.
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Papers by Chiara Passoni
A new research recently introduced the concept of holistic seismic, energy, and architectural renovation of existing buildings targeting resilience, safety, and sustainability. Integrated retrofitting techniques have been proposed, and a new structural design procedure has been studied rethinking existing approaches by including sustainability principles.
With reference to post-WWII RC buildings, which are often mid-rise isolated buildings located at the city outskirts, additional exoskeletons implementing the technologies and devices for an integrated upgrade have been proposed. Exoskeletons are entirely built from outside, thus avoiding the temporary dismissal of the buildings and the relocation of the inhabitants.
Both ‘shear wall’ or ‘shell’ solutions, either dissipative or over-resistant, can be envisioned for structural retrofitting. In the first solution, shear walls can be integrated in the new exoskeleton, whereas energy efficiency upgrading is guaranteed by the envelope, thus the two structure-energy systems work in parallel. In the ‘shell’ solution, the building envelope has both energy and structural functions.
In this paper, both over-resistant and adaptive diagrids are introduced for the holistic refurbishment of existing buildings.
Over resistant diagrids are conceived for the seismic upgrade of those buildings having stiff masonry infill walls and staircase walls, for which dissipative solutions may be ineffective unless massive preliminary interventions are carried out to downgrade the existing building initial stiffness.
Adaptive diagrids are conceived as over resistant ‘shell' structures to avoid any damage at the operational limit state, while dissipation is triggered through dissipative rigid-plastic supports to reduce shear at the grid foundations at the life safety limit state.
Selection of materials and technologies, enabling maximum adaptability, reparability and maintenance, and total demountability-recyclability/reuse at end-of-life is also discussed.
A global integrated intervention for the sustainable restoration of the considered building stock is proposed in this paper. The conceived approach overcomes the shortcomings of the traditional renewal practice, targeting uncoupled solution of single deficiencies. The solution also stems as an enhancement of past pioneering techniques, such as the double skin, focusing on architectural restyling and energy efficiency upgrade. In the proposed approach energy efficiency and structural upgrading measures are coupled, and the exoskeleton is complemented with ad-hoc systems and devices to increase structural safety and seismic resilience. The intervention is carried out from the outside, with reduced impairment of the inhabitants and building downtime. Unlike traditional energy efficiency interventions, the structural upgrade entails a series of co-benefits: it allows lengthening the building service life, thus representing a viable and more sustainable alternative to the building demolition and reconstruction practice; it increases seismic resilience at district level, reduces life cycle costs and minimizes environmental impact over the building life cycle.
Despite the research work be multidisciplinary, in this paper emphasis is made on the sole structural issues. The exoskeleton conceptual design is discussed and both over-resistant and dissipative solutions are proposed. Main principles of performance based design are presented, which allow minimizing the damage on the existing building. Finally, the case study of a typical residential building is presented, in which the possible use of the engineered double skin is proposed as an alternative to the basic double skin.