Experimental Campaign on the Seismic Response of Weak Clay Masonry Infills: In-Plane and Out-of-Plane Interaction via Shake Table Testing

Masonry infills, commonly integrated into reinforced concrete (RC) and steel-framed buildings, are typically regarded as non-structural elements. However, recent earthquakes have revealed their vulnerability to seismic actions, prompting extensive research into their seismic behaviour. Despite this, a review of the current literature highlights the need for further investigation to fully understand their dynamic response, particularly the influence of in-plane damage on out-of-plane performance. This paper presents a comprehensive experimental campaign currently ongoing at the Eucentre Foundation, aimed at examining the seismic behaviour of horizontally hollowed clay masonry infills—a typology widely used in Mediterranean countries during the 1960s–1980s. Full-scale, single-story, single-bay infill panels were constructed within steel-concrete composite frames and tested under various boundary conditions: fully connected on all edges, with top or side gaps, with different masonry unit thicknesses (12 cm and 8 cm), and with or without openings. The testing program included, for each configuration, in-plane pseudo-static cyclic tests, dynamic out-of-plane shake table tests, and combined sequential tests in which infills were first subjected to in-plane loading and then to dynamic out-of-plane shaking until collapse. Key objectives included understanding the in-plane and out-of-plane responses, their interaction, the effects of damage progression and boundary conditions on failure mechanisms, and the influence of opening presence and infill thickness. Significant findings were obtained regarding force-displacement relationships, damage propagation, acceleration and displacement distributions, and arching/bending behaviour, offering valuable insights for the seismic assessment and safer design of masonry infills. The experimental data are publicly available at https://experiments.builtenvdata.eu/datasets/43/.