Simplified multicriteria method for seismic assessment of unreinforced masonry buildings

The aims and motivations that were driven this PhD thesis arise from the common interest on the mitigation of the seismic risk, wide field of continuous relevance and of interest for different disciplines. The scientific community, specially in engineering field, reserves attentions on the mitigation of the seismic risk. The human and economic losses, caused by fragilities of the urban centres, manifested in the aftermath of a seismic event, confirm the need of research effort. The PhD thesis presents a multi criteria method for seismic assessment of unreinforced masonry buildings, URMs. The majority of the built environment consists of URMs. The study of their seismic behaviour is exasperated by the ageing of materials, the lack of anti-seismic criteria, construction process, architectural alterations or restorations, and the poor mechanical properties of used materials. Nevertheless, URMs are unique constructions for their historical and architectural value, that need to be protected against earthquakes. The knowledge of structural fragilities of urban centres is a prerequisite to face the mitigation of the seismic risk. Simplified assessment methods arise to overcome the effort and time consuming of analysis at a large scale of the built environment, by means the introduction of several simplifications. The proposed multi criteria vulnerability method provides a quick assessment based on few structural parameters, known from field observations and geometric survey, to overcome excessive computational demand, thanks to two different levels of evaluation. The first level of the vulnerability assessment method bases on the evaluation of few structural parameters to perform a first screening of the seismic fragilities. The second level predicts the seismic capacity of masonry walls more accurately respect to the empirical one, to establish strengthening measures or strategies more accurately. Therefore, the multi criteria method could support the activities of authorities and stakeholders in the mitigation of the seismic risk of the built environment. The thesis consists of eight chapters. The first chapter introduces an overview on the seismic risk, as field of the research activity. The second chapter concerns the state of the art of structural vulnerability, the structural vulnerability. An in-depth classification of seismic vulnerability assessment methods is reported. The third chapter regards the test-site of the research activity. The fourth chapter reports the dynamic campaign on a URM, chosen as representative of the structural class. The aim of this activity was to investigate the influence of a suite of structural parameters influencing the building behaviour. The fifth chapter introduces the first level of the predictive multi-criteria method. The empirical method aims to estimate the seismic vulnerability through the evaluation of a few structural parameters, ensuring a quick application. The derivation and validation of the formulations' method are reported. The last part of the chapter compares the method with others available from the literature, to highlight its reliability and advantages. The sixth chapter illustrates possible applications of the empirical predictive method. The seventh chapter discusses the second level of the proposed method. It aims to grasp the seismic vulnerability of buildings, with a higher accuracy than the first level. The eighth chapter completes the PhD thesis, with a broader point of view, to explain the results and future developments.