Seismic vulnerability assessment of the basilica of San Francesco in Arezzo

The paper discusses the seismic vulnerability of the Basilica of San Francesco in Arezzo (Italy). The church was investigated within a research project, promoted and financed by the Italian MIBACT, and the paper aims to show the methodology employed to develop the knowledge process and to evaluate the seismic risk. The information collected during the knowledge process, which included an experimental in-situ campaign, allowed to characterize the geometric and mechanical parameters required to perform a reliable structural assessment. The seismic assessment of the Basilica was performed according to the Italian “Guidelines for the assessment and mitigation of the seismic risk of the cultural heritage”1 (DPCM 2011) that identify a methodology of analysis based on three different increasing levels of knowledge of the structure. The first level of analysis (LV1) allows to evaluate the collapse acceleration of the structure by means of simplified models based on a limited number of geometrical and mechanical parameters. The second level (LV2) is based on a kinematic approach performed to analyse the local collapse mechanisms that can develop on several macro-elements. The last level of evaluation (LV3) requires a global analysis of the whole building under seismic loading by suitable numerical models. To perform the global analysis (LV3) the finite element modelling technique has been employed, where the nonlinear behaviour of masonry has been taken into account by proper constitutive assumptions. Seismic capacity has been evaluated using a pushover approach, and the results obtained with the nonlinear numerical model have been compared with the simplified schemes LV2 and LV1.