In-plane/out-of-plane interaction of strong masonry infills: From cyclic tests to out-of-plane verifications

The construction of RC frame structures with masonry infills is part of the traditional building practice in many European countries and worldwide. Several studies have been recently conducted to improve further the understanding of the seismic response of masonry infills, which are mainly focused on weak/slender clay masonry panels representing a common typology of the past, whereas very limited research has been devoted to stronger/thicker masonry infills, which nowadays are being adopted with increasing frequency in newly designed RC structures for their excellent thermal and acoustic performance. In order to fill this gap, within a systematic experimental and numerical research program, the in-plane and out-of-plane experimental response of ‘strong’ masonry infills has been investigated at the Eucentre and the University of Pavia. In particular, this paper presents the framework and discusses the results of out-of-plane static cyclic tests on full-scale, single-storey, single-bay RC frame specimens infilled with 35 cm thick tongue and groove clay unit walls, the related damage propagation and the failure mechanisms. The in-plane/out-of-plane experimental interaction evaluated in terms of stiffness and strength reduction and period increase in function of previous in-plane damage is also introduced, with the aim of providing a simplified out-of-plane strength verification within the European codified design procedures.