Chiara Passoni

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...

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, 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...

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 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...

The deep renovation of existing buildings is nowadays acknowledged as a priority in order to foster safety and eco-efficiency of the European construction sector. This renovation process should be inspired by some major principles as to ensure sustainability and feasibility of the interventions, also boosting the actual low renovation rate. The introduction of diagrid exoskeletons has been recently proposed as a new holistic and sustainable technique for the deep renovation of existing RC buildings under a seismic, energy, and architectural point of view. The exoskeleton can be conceived by addressing the Life Cycle Thinking principles, not also implementing eco-efficient materials but also guaranteeing reparability, adaptability, and demountability, selective dismantling and reusability of each component at the end of life. The solution is implemented exclusively from outside the building, thus avoiding inhabitants’ relocation. Off-site prefabrication of components, as well as the ...

In the last decades, sustainability has become a priority worldwide and the major objective of European policies defining future societal development. Being responsible for the greatest amount of GHG emissions, the construction sector -particularly the existing building stock- is acknowledged as among the major sources of environmental burden and as requiring urgent and serious renovation actions. Existing buildings need substantial retrofit interventions tackling their multiple deficiencies, concerning energy inefficiency, obsolescence and structural vulnerability. In this scenario new frameworks are required, which should overcome the fragmented nature of the current design standards in favor of a unitary approach, enabling the design of holistic renovation interventions. Such frameworks should as well acknowledge and propose solutions to overcome the major barriers to the renovation, while addressing new business models and integrating updated sustainable principles. In this pape...

A systematic action must be undertaken for a deep renovation of the existing building stock in order to pursuit a sustainable society and to boost the actual renovation rate; with this aim, new retrofit techniques should be envisioned. Among available techniques, in this paper, focus has been paid on steel diagrid systems. Diagrids have been introduced and investigated in the last years as bearing structures of tall buildings. When applied as retrofit solutions, diagrids are particularly suitable: they can be part of an integrated renovation project (energy, architecture, and structure); they can be carried out from outside (without requiring the inhabitants’ relocation); they can be built following an incremental rehabilitation strategy and in compliance with the Life Cycle Thinking principles. In this work an application of a diagrid system as retrofit solution is proposed as an extension of what presented by the authors during the XXVII CTA Congress.

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 dissipa...

The reinforced concrete (RC) 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 multi-purpose retrofit strategy addressing in particular both energy and structural issues is therefore necessary. The present paper considers the sole seismic retrofit interventions by investigating the suitability of external RC walls hinged connected at their base, suitable to improve the seismic performance of poorly detailed existing RC buildings. In particular, such a solution avoids the concentration of deformation at one storey of the building, i.e. the development of soft story mechanisms, and reduces the demand on the foundations of the new system, being the bending moment at the base of such walls nearly zero. The paper shows, through non-linear pushove...

Traditional seismic retrofit of historical masonry buildings is mainly aimed at inhibiting local mechanisms and at engaging the whole building into a box-like structural behavior through either perimeter ties, or floor and roof diaphragms. When the adoption of “minimally impairing” perimeter ties is unviable, floor and roof diaphragms are usually adopted. The effectiveness of such interventions requires careful design and detailing of their connections to the perimeter walls, which enable shear flow transfer from the out-of-plane loaded masonry walls to the diaphragms and from the diaphragms to the seismic resistant walls. Focus is made on the assessment of the structural performance of the connections of roof diaphragms to the perimeter walls. Stud connectors are investigated and a possible technical solution improving the connection capacity is presented. In the case of historic masonries, theoretical and numerical prediction of the connection capacity may be unviable because of t...

The concept of resilience can be applied to postwar buildings, which are increasingly exposed to seismic events. Today this threat can be dealt with through preventive practices, based on the use of adaptive exoskeletons: prosthetic systems that identify a field of experimentation marked by an undoubted social, environmental and economic value. This technique is based on a design that simultaneously allows seismic upgrade , energy retrofit , plant-engineering adjustment and the remodelage of those structurally, aesthetically and functionally obsolete and highly vulnerable residential buildings, on which resilience can activate targeted policies aimed at the preservation of human life, environmental sustainability and the rational use of the scarce economic resources available.

The deep renovation of existing buildings is nowadays acknowledged as a priority in order to foster safety and eco-efficiency of the European construction sector. This renovation process should be inspired by some major principles as to ensure sustainability and feasibility of the interventions, also boosting the actual low renovation rate. The introduction of diagrid exoskeletons has been recently proposed as a new holistic and sustainable technique for the deep renovation of existing RC buildings under a seismic, energy, and architectural point of view. The exoskeleton can be conceived by addressing the Life Cycle Thinking principles, not also implementing eco-efficient materials but also guaranteeing reparability, adaptability, and demountability, selective dismantling and reusability of each component at the end of life. The solution is implemented exclusively from outside the building, thus avoiding inhabitants’ relocation. Off-site prefabrication of components, as well as the ...

In the last decades, sustainability has become a priority worldwide and the major objective of European policies defining future societal development. Being responsible for the greatest amount of GHG emissions, the construction sector -particularly the existing building stock- is acknowledged as among the major sources of environmental burden and as requiring urgent and serious renovation actions. Existing buildings need substantial retrofit interventions tackling their multiple deficiencies, concerning energy inefficiency, obsolescence and structural vulnerability. In this scenario new frameworks are required, which should overcome the fragmented nature of the current design standards in favor of a unitary approach, enabling the design of holistic renovation interventions. Such frameworks should as well acknowledge and propose solutions to overcome the major barriers to the renovation, while addressing new business models and integrating updated sustainable principles. In this pape...

A systematic action must be undertaken for a deep renovation of the existing building stock in order to pursuit a sustainable society and to boost the actual renovation rate; with this aim, new retrofit techniques should be envisioned. Among available techniques, in this paper, focus has been paid on steel diagrid systems. Diagrids have been introduced and investigated in the last years as bearing structures of tall buildings. When applied as retrofit solutions, diagrids are particularly suitable: they can be part of an integrated renovation project (energy, architecture, and structure); they can be carried out from outside (without requiring the inhabitants’ relocation); they can be built following an incremental rehabilitation strategy and in compliance with the Life Cycle Thinking principles. In this work an application of a diagrid system as retrofit solution is proposed as an extension of what presented by the authors during the XXVII CTA Congress.

The reinforced concrete (RC) 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 multi-purpose retrofit strategy addressing in particular both energy and structural issues is therefore necessary. The present paper considers the sole seismic retrofit interventions by investigating the suitability of external RC walls hinged connected at their base, suitable to improve the seismic performance of poorly detailed existing RC buildings. In particular, such a solution avoids the concentration of deformation at one storey of the building, i.e. the development of soft story mechanisms, and reduces the demand on the foundations of the new system, being the bending moment at the base of such walls nearly zero. The paper shows, through non-linear pushove...

The concept of resilience can be applied to postwar buildings, which are increasingly exposed to seismic events. Today this threat can be dealt with through preventive practices, based on the use of adaptive exoskeletons: prosthetic systems that identify a field of experimentation marked by an undoubted social, environmental and economic value. This technique is based on a design that simultaneously allows seismic upgrade , energy retrofit , plant-engineering adjustment and the remodelage of those structurally, aesthetically and functionally obsolete and highly vulnerable residential buildings, on which resilience can activate targeted policies aimed at the preservation of human life, environmental sustainability and the rational use of the scarce economic resources available.

The article focus on the development of a one-part alkali activated slag-based lightweight plaster for seismic retrofitting and energy upgrading of poor-quality stone masonry buildings. Two different alkali activated mortars were manufactured by using expanded glass aggregates and air entraining agent in order to guarantee the mechanical compatibility with historic stone walls (28-day compressive strength close to 8 MPa) and, at the same time, a low thermal conductivity by means of a low specific mass (< 1000 kg/m3). Experimental results evidenced that alkali activated plasters are 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/m3. Furthermore, by using methylcellulose (MC), modified starch (MS), polypropylene fibers and shrinkage reducing admixture (SRA), the shrinkage of mortars was strongly reduced and excellent adhesion to the substrate, absence of micro-cracks and detachments were achieved.

The improvement of seismic performances and the enhancement of the energy efficiency of existing buildings have nowadays become a priority. Indeed, much of the existing building stock is characterized by great structural, architectural and thermal obsolescence. In addition to the renovation of existing buildings, a very important aspect is the repair and upgrading of buildings recently damaged by the seismic events that hit the Italian territory. In particular, this article takes into account a school located in the municipality of Pievebovigliana, province of Macerata, which got damaged by the earthquakes that hit Central Italy on 24.08.2016 and 30.10.2016. In detail, the article refers to a one-story building characterized by an irregular plan configuration. The gravity load resisting system is made by masonry walls with regular blocks; in addition, few reinforced concrete columns embedded in the masonry walls support the roof girders. Different strategies of anti-seismic retrofit...

In recent years the redevelopment of the post-World War II reinforced concrete heritage has become an essential action to meet energy-saving and to foster safety and resilience of European communities. In order to overcome the major barriers to the renovation, new solutions should follow a holistic approach, thus solving the structural, energy and architectural deficiency at the same time. The interventions should be carried out from outside the building, so as to leave the building use unaltered, with no need of user relocation, and Life Cycle Thinking (LCT) principles should be addressed. In this paper, these main pillars are translated into an innovative technology, the steel diagrid exoskeleton, for which a proportioning criterion is proposed, besides the assessment of its effectiveness as a seismic risk mitigation measure. Among possible structural typologies, diagrids are particularly interesting for their remarkable architectural potential and for the possible standardization...

The majority of the European buildings is characterized by high energy consumption, technological obsolescence, and living discomfort. Moreover, these buildings have exhausted their structural service life (50 years) and may be structurally unsafe. In this paper, an integrated deep renovation solution for the seismic retrofitting, energy efficiency upgrade and architectural restyling of existing concrete buildings is proposed. More specifically, the performance of a technological-structural shell made of pre-fabricated, insulated panels is presented. The structural shell enforces a box-structural behavior of the existing building, while improving energy efficiency. The intervention is conceived to be entirely carried out from outside the building, without causing any disruption in the building use. The new shell can either adhere to the existing structure, as a thermal-structural coating layer, or can be located with an offset, thereby enabling remodelage interventions to include ba...

Considering the renovation of the existing building stock, it is necessary to develop integrated solutions aimed at the simultaneous reduction of the energy consumption, the improvement of the structural performance and, where necessary and possible, the architectural restyling of the buildings. These are measures that maximize resilience and safety and minimize the environmental impact of the existing buildings. Such interventions are designed to be conducted mainly from the outside, minimizing the disturbance caused to users. These integrated renovating projects can be effectively conducted based on the Life Cycle approach as well as following the Performance Based Design (PBD). The combined use of both methodologies maximizes the structural and energy performance of the building, while minimizing, at the same time, the environmental impact of the intervention, the overall cost of the intervention and the operational costs. The article shows a feasibility study of the upgrading st...

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/m3). 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/m3. 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 th...

In recent years, the transition to a sustainable society has highlighted the importance of tackling a holistic renovation of the existing building stock, able to contextually solve its structural, energy, and architectural deficiencies. Nevertheless, in practice, the cost of the intervention, the building downtime, and the potential relocation of the inhabitants have been recognized as major barriers to the renovation. To overcome such barriers and foster sustainability, eco-efficiency, and resilience, new design approaches and solutions sets have been proposed. However, given the lack of a global vision of current regulations, a design framework able to conjugate technical and functional performances with principles of sustainability and feasibility is still required. In this paper, a new multi-step design framework is proposed, which, for the first time: 1) adapt the three pillars of sustainability to the renovation of the existing buildings interpreting them as reduction of envir...

The renovation of the post-World-War-II reinforced concrete building has become an urgent action in order to meet energy-saving and to foster safety among the European communities. In this context, in order to overcome the major barriers to the renovation and to increase the feasibility of a deep, sustainable renovation action, a new incremental holistic rehabilitation (IHR) approach is introduced. This new approach has the major aim of fostering a safe, resilient and more sustainable society by addressing the life cycle thinking principles and by implementing incremental levels of safety. In this paper, an IHR strategy is defined and applied to a reference scholastic building. Fundamental criteria for the selection of the proper renovation strategy guaranteeing the minimum environmental impact and the applicability to Reinforce Concrete existing infilled frames are derived. The results show that a holistic incremental rehabilitation strategy can represent a good answer to the urgen...

When is demolition mandatory? To date there is a lack of specific tools and protocols enabling a rigorous scientific assessment of the deterioration level of existing structures, guiding the choice between the real possibility of renovation or the unavoidable need of demolition. In the present paper, an attempt is made to develop a protocol suitable to assess the actual capacity of existing structures and predict their future behaviour based on inspection and diagnosis of the building. The potential benefit of such a tool is to help detecting the best intervention strategy making the renovation process more sustainable and efficient. Toward this perspective, a critical analysis and comparison of literature models on the residual capacity of structural elements has already been carried out by the authors. The assessment of the preservation state is herein further extended to the overall structural level, by proposing a new approach relating the performance of deteriorated elements ov...

The construction sector corresponds to the largest industrial sector not only in economic terms, but also in terms of resource flow. Moreover, European citizens spend most of their lives inside buildings, therefore buildings turn out to be at the centre of social and economic activity. In that light, Europe is involved in several initiatives and strategies aimed at making this sector one of the most competitive and innovative, focusing on the achievement of the environmental and energy targets in line with 2020 Europe Strategy and EU 2050 roadmap, but also ensuring safety both in ordinary conditions and in presence of exceptional events, such as earthquakes. While new buildings can be constructed with high performance levels, the older buildings typically need renovation measures, because of their low energy performance and seismic vulnerability. This report has the aim to define the research needs for exploiting old buildings potential to deliver energy and CO2-emission savings and seismic performance improvement, as well as societal and economic benefits, so that energy efficient and earthquake resistant buildings can have a pivotal role in a sustainable future. In the first part of the report, a detailed analysis of the main characteristics of European buildings in terms of age, size, ownership, location, structural typology is presented in order to define the predominant typology of the European existing building stock; the seismic hazard in Europe and the earthquake vulnerability of European buildings are then analysed; and finally, energy consumptions and environmental impacts in terms of use of resources, construction and demolition (C&D) wastes and CO2 emissions are described. The analysis of the present situation turns out to be essential in order to define the starting point to assess the current and new technology options, examined in the second part of the report and necessary to obtain eco-efficient and seismic resistant buildings. In addition, benefits that a renovation project could bring against a demolition and reconstruction programme have been underlined. Once these inputs have been defined, the requalification needs and the importance to improve renovation strategies, considered as outputs of the analysis, are examined for each of the two abovementioned parts of this study. Finally, a critical discussion on the importance of considering research needs for this topic has been carried out, with a focus on barriers and challenges that could be found during a renovation programme.