FRAGILITY CURVES FOR ROCKING MASONRY FAÇADES OF CHURCHES: A SENSITIVITY STUDY OF VULNERABILITY PARAMETERS

Out-of-plane failure of façades is one of the most distinctive local mechanisms in masonry churches recognizable in the aftermath of a seismic event. The purpose of this paper is to de-rive large-scale fragility curves for masonry church façades using incremental static analysis, and to assess the influence of some parameters on their vulnerability. According to the dis-placement-based approach, pushover analysis is carried out considering both the geometric nonlinearities and the stabilizing contribution of frictional resistances exerted by the church sidewalls. The seismic demand is derived using acceleration-displacement response spectra (ADRS) for different limit states, obtained according to the Italian seismic code. The analyses are addressed with reference to a large sample of masonry churches generated starting from the geometric parameters of a reduced sample of churches hit by the seismic event of 21st Au-gust 2017 in the Ischia Island (Italy). Several geometric aleatory variables, i.e. the length, the height and the thickness of the façade, are treated by means of the Monte Carlo simulation (MCS) to generate a numerical sample of 400 facades. Considering two limit states for rock-ing (moderate and severe motion), fragility curves are derived for these facades subjected to the same single ground motion scaled at different values of PGA, using incremental static analysis (ISA) and multiple stripe analysis (MSA). Finally, on the same sample of 400 fa-cades, the sensitivity of the fragility curves to the friction coefficient, the length of masonry units and the position of the façade mass center is investigated.