Out-of-plane behaviour of prefabricated damped infill wall panels in a steel frame: Experimental and numerical investigation

The prefabricated damped infill wall panel (PDIWP) for steel frames is an innovative system that can reduce the in-plane (IP) diagonal action of the traditional prefabricated infill wall panel (TPIWP) by introducing friction-based damping layer joints (FBDLJs). However, the out-of-plane (OOP) behaviour of the PDIWP, which plays a critical role in its overall seismic performance, remains unclear. This study investigates the OOP response and resistance mechanisms through experimental testing and parametric analysis. The results indicate that each wall panel underwent independent horizontal bending, with vertical cracks primarily concentrated at the midspan, and frictional sliding developed within the FBDLJs, leading to a stepwise OOP displacement pattern. Due to isolation gaps between precast wall sub-panels (PWSPs) and columns, as well as significant relative movement between PWSP and the top beam, arching action was inhibited, resulting in peak load and initial stiffness reductions of 47.94% and 60.68% compared with the TPIWP, respectively. Nevertheless, the PDIWP was able to resist the maximum OOP seismic force demands specified for the highest seismic regions. Owing to the steel material ductility of the T-shaped connectors which yielded in bending but remained intact without fracture, the PDIWP maintained a highly stable post-yield load-transfer path and outstanding deformation capacity without collapse up to a displacement of 1.0 times the wall thickness. Numerical investigation further confirms that enhancing concrete and reinforcement strengths improves the OOP capacity without altering the failure mechanism, whereas an excessively large connector width-to-thickness ratio restricts the post-yield capacity due to compromised panel-to-panel deformation compatibility.