Experimental out-of-plane seismic response of URM gables

Abstract

Low-rise masonry buildings around the world often include unreinforced masonry (URM) walls combined with pitched roofs that are supported or enclosed by masonry gables. Such buildings constitute a significant portion of the built environment in several earthquake-prone regions, affected by either natural or induced seismicity. Masonry gables in these structures have repeatedly shown high seismic vulnerability to out-of-plane excitations, as documented in post-earthquake survey studies. This paper presents the main outcomes of an experimental campaign carried out within the ERIES-SUPREME project to increase the understanding in URM gable out-of-plane seismic response. Three full-scale, densely instrumented gable specimens were tested using a dual shake-table configuration and subjected to incremental dynamic excitations up to collapse, simulating both induced and tectonic earthquake scenarios. The experimental tests examined the influence of differential motions between the top and base of the gable wall, either linearly amplified or both amplified and out-of-phase, implemented by the two tables to reproduce the interaction with three distinct roof diaphragm configurations. Experimental results are discussed in terms of observed failure mechanisms, hysteretic force-displacement behaviour, as well as acceleration and displacement capacities. In particular, increasing roof diaphragm flexibility leads to earlier activation of the out-of-plane failure mechanism and to a marked reduction in collapse acceleration at the gable base, while the acceleration at ridge level provides a more consistent representation of the effective seismic demand acting on the gables.