Out-of-plane seismic response of masonry façades: a comparison among full dynamic and pushover analyses

The paper is focused on the seismic risk assessment of monumental masonry buildings, and more specifically on the analysis of out–of–plane mechanisms which actually represent the most recurrent collapse mode for the fac¸ade of buildings such as churches or basilicas. The full Nonlinear Dynamic (ND) modelling of the seismic response is performed by adopting a specific rigid body and spring model, RBSM, where damage is ascribed to the out-of-plane flexural behaviour. A phenomenological description of the cyclic response of the masonry material is provided in the definition of the constitutive prescriptions, including hysteretic and degrading material behaviour. Then, a comparison is made with a non linear static pushover (NSP) analysis , which is performed by means of the same specific RBSM under quasi-static loading, incrementally applied. The seismic response in terms of generalized force–displacement curve and the ultimate limit displacement capacity are evaluated, comparing them with the seismic displacement demand, expressed in terms of spectral coordinates. The two different approaches are compared by considering as a case study the church of Rosario, in Guastalla, which was damaged by Emilia Romagna Earthquake (1987). A number of analyses have been performed, investigating a variety of different aspects concerning the accelerogram records and their correlation with the damage indicators of the non-linear models.