Seismic fragility curves via nonlinear dynamic analyses: derivation for three unreinforced masonry school buildings

This research deals with the seismic risk assessment of existing masonry buildings and, more specifically, it focuses on the fragility component, i.e. the development of fragility curves. In the paper, fragility curves are derived by using a numerical approach, based on the execution of nonlinear dynamic analyses (NLDA) according to the Cloud Method. Among other possible different approaches (i.e. empirical, analytical-mechanical based, hybrid), the numerical approach has been selected as one of most suitable when the risk study is addressed to portfolio of buildings, like the examined case that focused on Italian unreinforced (URM) schools. In the paper, the adopted procedure to interpret the huge data provided by NLDA and convert them into the attainment of synthetic damage level is described. It has been tentatively applied to three URM schools. Finally, mechanical-analytical fragility curves and residential fragility curves, already available in literature, were used to compare and validate the derived numerical fragility curves.