Effect of Opening Location and Size on the In-Plane Lateral Performance of Unreinforced Masonry Walls: A Zone-Based Numerical Study

Abstract

Unreinforced masonry (URM) walls with openings exhibit complex in-plane lateral behavior that is governed not only by the size of the opening but also by its longitudinal and vertical position within the wall. Despite this, most existing studies characterize the structural impact of openings solely through the Total Perforation Ratio, without accounting for the positional sensitivity of the opening relative to the internal diagonal load path. This study presents a numerical parametric investigation into the effect of opening location and size on the in-plane lateral performance of URM walls using a Simplified Micro-Modeling framework implemented in ABAQUS. The wall length was discretized into three longitudinal zones: Zone I (loaded side), Zone II (central), and Zone III (passive side); and openings of three area sizes (3.70%, 6.17%, and 8.64%) with corresponding aspect ratios of 0.85, 1.41, and 1.97 were systematically positioned at multiple vertical locations within each zone, yielding twenty-three perforated wall models. Lateral strength, initial stiffness, and failure pattern were evaluated relative to a solid wall reference model. Results demonstrate that Zone II produces the most severe strength reductions, reaching 51.56% for mid-elevation openings that directly sever the diagonal compressive strut. Bottom-positioned openings in Zone III prove equally critical, with reductions reaching 57.22% due to elimination of the strut anchor at the passive corner. Initial stiffness degrades monotonically with increasing opening area, with maximum reductions of 33.54%, 36.13%, and 31.59% in Zones I, II, and III, respectively. The failure mechanism varies systematically from diagonal tension to rocking-dominated toe crushing as opening size increases and location shifts toward the passive side.