Experimental assessment of the out-of-plane seismic response of URM infill walls

In-plane behaviour of unreinforced masonry infills has been widely investigated in the past, while a deeper knowledge on their out-of-plane seismic response is yet necessary to prevent out-of-plane collapse and its detrimental effects on human life safety shown by recent earthquakes. In this paper, a state-of-the-art review on the experimental tests carried out in the past to investigate the out-of-plane behaviour of infills is presented. An experimental program aimed at assessing the influence of different boundary conditions on the lateral strength and displacement capacity of thin URM infill walls is described and its results discussed. Pseudo-static tests carried out to investigate the influence of in-plane damaging on the out-of-plane behaviour of infills, i.e., the in-plane/out-of-plane interaction effects, are described. Based on the experimental tests’ results, an out-of-plane strength degradation curve is presented and compared with the prediction of literature models and with the results of previous experimental programs in order to discuss the effects of infills’ slenderness on their out-of-plane strength reduction due to in-plane damaging.