Seismic vulnerability analysis of historic masonry buildings with multi-mode failure modelling

The poor seismic performance observed in existing masonry buildings, for instance after recent strong earthquakes in Italy, calls for further advances in their structural assessment and vulnerability modelling. Over the years, this has become a fundamental condition for development of new seismic risk prevention and reduction strategies, due to the great variability in the typological characteristics and failure mechanisms of masonry buildings. The aim of the present work is to investigate the structural behaviour of historical masonry buildings, analytically assessing their seismic vulnerability through a methodology that accounts for both in- plane (IP) and out-of-plane (OOP) failure modes of load-bearing walls. Based on the integration of statistical data and information from the literature, representative building archetypes of Italian historic buildings are defined, and thus structural models are developed to which existing buildings can be related to on the basis of constructional similarities. Seismic response of building archetypes was first analysed through a MATLAB code based on equivalent frame modelling (EFM) and nonlinear static analysis, taking into account IP failure mechanisms. The same buildings were then assessed with the FaMIVE procedure, which produces capacity curves for OOP failure mechanisms based on a limit state analysis approach. The fragility curves were derived for each of the two procedures and compared to each other. The paper concludes with an illustration and discussion of the analysis results, which allows highlighting the methodology's potential to assess the regional- scale vulnerability of the historical masonry buildings.