Nonlinear modelling of the in-plane-out-of-plane interaction in the seismic analysis of masonry infills in r.c. framed buildings

A five-element macro-model, with four diagonal out-of-plane (OOP) nonlinear beams and one horizontal in-plane (IP) nonlinear truss, takes into account the OOP and IP failure modes occurring, in the event of seismic loading, for masonry infills (MIs) inserted in reinforced concrete (r.c.) framed buildings. Pivot hysteretic models predict the nonlinear IP and OOP force-displacement laws of the infill panel, based on geometrical rules defining loading and unloading branches. Firstly, a calibration of the proposed IP-OOP interaction model of MIs is carried out considering full-scale experimental results of traditional masonry typologies. To evaluate the interaction, the numerical results of simultaneous IP and OOP cyclic tests on MIs at the top, intermediate and lowest levels of an existing six-storey r.c. framed building are presented, assuming different displacement histories: i) OOP loading faster than IP, at the sixth storey; ii) equal IP and OOP loading, at the third storey; iii) IP loading faster than OOP, at the first storey.