A masonry infill wall model with in-plane—out-of-plane interaction applied to pushover analysis of RC frames

After many recent seismic events, heavy damage and failures of unreinforced masonry (URM) walls proved to be both a considerable economical loss and a serious hazard for human safety. Despite being classified as non-structural elements and often neglected in design numerical models, URM infills have a relevant influence on the seismic behaviour of structures. Simple and more refined models for URM infill walls have existed for decades, but usually they refer only to in-plane actions. Recently, however, a few macromodels that include out-of-plane actions were proposed, but limited studies have shown their application to realistic reinforced concrete (RC) frame structures. The aim of this work is to adopt and calibrate a macro-model for masonry infill walls that considers simultaneous in-plane and out-of-plane actions, and apply it to the nonlinear pushover analysis of RC frame structures representative of traditionally and seismically designed buildings. To this scope, a recently proposed URM infill macro-model with in-plane out-of-plane interaction is calibrated with existing experimental data from quasi-static tests performed on two types of clay masonry infill walls that are commonly found both in Italy and other Mediterranean countries. The calibrated elements are included in planar numerical models of RC framed structures representative of the Italian building stock, considering both traditionally and newly designed frames. Nonlinear static pushover analyses are performed on the frames with simultaneous static forces acting on the walls elements in the out-of-plane direction. Increasing the out-of-plane loads induces both cracking and failure of the walls at lower lateral drifts of the buildings and also affects the overall response curve of the frames.