RINTC project: nonlinear dynamic analyses of Italian code-conforming URM buildings for collapse risk assessment

This paper deals with the computation of the collapse risk of new masonry buildings designed according to the Italian Building Code. Companion papers describe the overall EUCENTRE-ReLUIS joint research project, funded by the Italian Department of Civil Protection (DPC), which considers different building types (r.c., steel buildings, etc) and uses multi-stripe nonlinear dynamic analyses by properly selected ground motion records. 2- and 3-storey unreinforced masonry buildings have been designed in cities with increasing seismic hazard, considering two different soil conditions at each site. First, the paper describes geometry, material characteristics (clay block masonry) and main structural details of the buildings, discussing the effect of different design methods (rules for simple buildings, linear and nonlinear static analysis) and models (cantilever or equivalent-frame models). The models used for the assessment by nonlinear dynamic analyses are equivalent-frame models made by masonry piers and spandrels, as well as reinforced concrete members. Two alternative macroelement models are used for the in-plane response of masonry members. Out-of-plane failure modes are assumed to be prevented by the presence of ring beams and limited slenderness of masonry walls. Pushover analyses are used to esti-mate the EDP (maximum inter-storey drift ratio) threshold for the collapse limit state. Finally, the results of the multi-stripe analyses are presented for 10 different earthquake's return periods.