Combined in-plane and out-of-plane seismic effects on masonry infills in RC frames

Unreinforced masonry (URM) infills, classified as non-structural elements and often neglected in design models, highly affect the seismic behaviour of RC frames increasing the global structural stiffness; furthermore, the in-plane (IP) damage of panels highly reduces their out-of-plane (OOP) resistance, anticipating soft-floor mechanisms. This paper presents a FE macro-model to simultaneously simulate the IP-OOP infill behaviour, calibrated for two different types of URM panel using experimental results. The goal is to investigate the seismic response of RC infilled frames considering earthquake directional effects. Nonlinear static analyses with different load-pattern directions are performed on traditionally and seismically designed frames. Results are presented using pushover curves, ductility indexes and resistant Peak Ground Acceleration associated to the achievement of infill and frame Limit States. IP/OOP interaction considerably affects both the global resistance and the infill Limit States in case of thin panel, and the frame Ultimate Limit State in case of thick panel.