Out-of-Plane Seismic Assessment of URM Infill Walls through Parametric Analysis

Out-of-plane (OOP) collapse of unreinforced masonry (URM) infill walls is a critical vulnerability in reinforced concrete (RC) buildings during seismic events. Although often overlooked in seismic design due to their classification as non-structural components, these infills can significantly affect building performance because of their geometric slenderness and brittle failure modes. This study builds upon a analytical model based on plate behaviour to perform an extensive parametric investigation. The influence of key parameters—such as aspect ratio (Lp/Hp), slenderness (Hp/tp), masonry strength, and perforation direction—is systematically evaluated. The results are summarised into simplified design charts that offer practical tools for preliminary assessment, seismic verification, and prioritisation of retrofit interventions. The proposed framework aims to enhance the integration of OOP performance criteria in the seismic assessment of non-structural elements.