Shaking Table Tests of Masonry Vertical Spanning Strip Walls: Energy Dissipation, Overturning Spectrum and Fragility Analysis

Unreinforced masonry structures exhibit significant vulnerability to seismic loading due to their considerable mass, intrinsic material brittleness, limited tensile capacity, and the frequent absence of stiff diaphragms or effective interconnection between structural components. Among their possible failure mechanisms, out‐of‐plane collapse is particularly critical when earthquake actions act perpendicular to the wall thickness, as it is characterised by low resistance. A commonly observed out‐of‐plane response occurs in walls with restraints at the top and bottom boundary conditions, which develop a three‐hinge mechanism and form what is referred to as a vertical spanning strip wall (VSSW). Experimental studies on VSSWs are still scarce, offering insufficient insights into the probabilistic assessment of their response and potential overturning, while existing experimental evidence on energy losses shows inconsistencies when compared with theoretical predictions. This paper presents a comprehensive experimental study aimed at advancing the understanding of the dynamic behaviour of VSSWs. Six configurations of dry‐stacked granite walls are examined, encompassing two height‐to‐width ratios and three overburden conditions. Detailed material characterisation is conducted for both the granite units and their interfaces, with the latter having a significant influence on the rocking response. The experimental campaign consists of over 350 shaking table tests, including both free‐ and forced‐vibration tests. The free‐vibration study provides key insights into the identification of the experimental hinge height, period‐amplitude relationships, and energy dissipation quantified through the coefficient of restitution. The forced‐vibration tests address the VSSW behaviour from multiple perspectives. First, simplified pulse excitations are used to construct, for the first time, an experimental rocking overturning spectrum. Subsequently, the response under recorded ground motions is examined within a probabilistic framework, from which experimentally informed limit states together with corresponding fragility curves are defined, providing valuable insights for the performance‐based seismic assessment of unreinforced masonry walls.