Probabilistic seismic response analysis of existing masonry structures

Masonry buildings represent a large and important portion of the existing building stock in several countries. They are still being built and nowadays they are mainly used as residential buildings, offices or for other activities. Most of these buildings are not designed to withstand earthquake-induced forces, therefore seismic safety assessment represents a crucial task to estimate risk level and eventually define retrofit measures. This task is hampered by the many uncertainties affecting the acquired data on plan and elevation geometry, material properties, connections between walls and roof, connections between walls and walls, seismic actions. The present paper intends to give a contribution in dealing with such uncertainties by applying a global probabilistic analysis on different masonry structural units. Such approach is based on the Italian seismic code and relies on a simplified non-linear assessment method. Purposely developed codes have been used for deriving the equivalent bilinear constitutive laws of floors and of the entire structural unit. Afterwards, a fully probabilistic Monte Carlo-based analysis has been performed by including and consistently modeling all uncertainties affecting the structural response. Capacity-demand ratios and failure probabilities have been evaluated for every considered structural unit. The subsequent sensitivity analyses have allowed for identification and quantification of the effect of all considered variables on the global response. Some interesting remarks on results obtained have been developed in order to progress towards a reliable and simple assessment procedure.