OUT-OF-PLANE RESPONSE OF MASONRY CHURCH FACADES INCLUDING P-DELTA EFFECTS

Out-of-plane rocking mechanisms represent one of the major causes of damage and failure for unreinforced masonry buildings, monuments and churches leading to significant economic and social losses every year in many regions throughout the world. Due to their slenderness, masonry walls subjected to rocking mechanisms can show large displacements before the complete overturning. Therefore, seismic analyses should consider geometrical nonlinearities, requiring more complex formulations and increasing the computational effort. This paper applies a recently proposed P-Delta formulation of the discrete macro-element method (DMEM) to analyse the seismic behaviour of masonry façades interacting with lateral walls. The model accounts for geometrical nonlinearities considering the P-Delta effects by updating the load vector at each step of the analysis, avoiding assembling and updating the geometrical stiffness of the system. In addition, the capability of the model to describe the coupled in-plane and out-of-plane wall responses allows for describing spatial failure mech-anisms. The presented study aims at quantifying the role of the P-Delta effects in conjunction with the cohesive-friction connections between the façade and lateral walls on the ultimate rocking of the external façade. These effects are here investigated through pushover analyses on a church façade. The analyses are conducted on a global model, accounting for brick interlocking, and on a simplified model, including only the façade where ad hoc calibrated non-linear links simulate the interaction with the lateral walls. The results show that geometrical nonlinearities affect the façade’s response even at relatively low-magnitude displacements, with increasing influence as the quality of the façade-to-lateral-walls connections reduces.