Dottorato in INGEGNERIA STRUTTURALE E GEOTECNICA

Titolo della tesi: Pre- and post-earthquake safety evaluation and loss assessment of reinforced concrete buildings

The severe socio-economic consequences of recent catastrophic earthquakes worldwide have further highlighted the high seismic vulnerability of existing buildings, as well as the crucial need to define and implement a medium-to-long-term plan for seismic risk mitigation in many earthquake-prone countries worldwide. Moreover, in addition to a seismic prevention plan, advanced post-earthquake emergency-management strategies are deemed critical for building up a more resilient community. In the aftermath of an earthquake, both rapid surveys and detailed assessments of the seismic residual capacity of earthquake-damaged buildings are required to support the decision-making process of re-occupancy and repair vs. demolition. Thus, reliable and standardized procedures are needed for the detailed evaluation of the expected performance of existing buildings - in terms of both safety and socio-economic consequences – in either their intact or damaged condition and support the implementation of adequate retrofit/repair strategies. Within this context, a significant research effort has been carried out in the last decades to propose advanced assessment frameworks able to provide a detailed description of the seismic performance of the structure by performance metrics of major interest for the stakeholders (e.g., repair cost, downtime, and casualties). Nevertheless, for practical applications, rapid and easy-to-apply (yet reliable) procedures could be preferred by different end-users/stakeholders, depending on their needs and the number and importance of the buildings. Moreover, when dealing with large-scale applications, the relevant building data collection may be challenging, often leading to limited building knowledge. Therefore, research effort is still needed to develop simplified, adaptive, and updatable methodologies/frameworks/tools to support the seismic-risk assessment of buildings. Considering the previous background, this Thesis aims to (1) investigate and propose simplified procedures for the seismic performance assessment of existing buildings in either pre- and post-earthquake scenarios and (2) develop adaptive and updatable frameworks for knowledge-based seismic risk assessment at a large scale. The Thesis initially provides a background and research motivations, as well as an overview of the seismic assessment methodologies for either intact and/or damaged buildings developed at the international level and adopted in the main building codes and guidelines. A particular focus is given to Reinforced Concrete (RC) structures, representing a wide part of the European building stock. Then, in line with the state-of-the-art methodologies for seismic risk assessment, a simplified procedure to develop state-dependent fragility relationships is proposed, based on nonlinear static analyses and a spectrum-based approach. The effectiveness of the proposed procedure is confirmed through a comparison with a more-refined state-dependent fragility estimation on multi-storey RC buildings. An application of the proposed methodology to a case-study RC building is also presented, evaluating both pre- and post-earthquake collapse risk and economic loss considering different damage states. Moreover, the Thesis investigates and discusses a simplified multi-knowledge seismic assessment methodology, involving the analytical-mechanical SLaMA (Simple Lateral Mechanism Analysis) method, for large-scale applications. The simplicity of the SLaMA method allows for its implementation even in the case of limited or incomplete building knowledge, thus directly accounting for the related uncertainties. In these cases, the multi-knowledge assessment procedure provides a range of possible capacity curves, and the dispersion in the results can be reduced if more building data are collected. An illustrative application to case-study schools in Italy is thus presented. Finally, the Thesis addresses the problems related to an integrated seismic-and-energy requalification of the building stock, investigating and proposing a simplified predictive model for the energy consumption of schools in Italy and the costs and benefits of possible refurbishment intervention scenarios. An extensive database, involving the results of refined energy analyses of school buildings in south Italy, is used to implement the study. The applicability of the proposed predictive model in a framework for the preliminary design of energy refurbishment interventions is also discussed through an illustrative application.