In-Plane Shear Strength Characteristics of Masonry Walls with Varying Mortar Types and Aspect Ratios: An Experimental and Numerical Study

This study examines the in-plane shear performance of clay-unit unreinforced masonry (URM) walls subjected to quasi-static cyclic loading, focusing on the simultaneous effects of mortar type and aspect ratio. Six full-scale wall specimens were tested using three mortar types—lime mortar (LM), cement mortar (CM), and lime-cement mortar (LCM)—and two aspect ratios of 0.95 and 1.93. Experimental results showed that mortar type had a more significant impact on failure behavior than aspect ratio. CM and LCM walls exhibited flexural rocking or sliding shear failures depending on the aspect ratio, while LM walls consistently displayed diagonal shear cracking irrespective of geometry. CM walls achieved up to 48% greater peak lateral strength compared to LM walls; however, LM walls exhibited superior energy dissipation and equivalent damping. Finite-element (FE) simulations using a macromodeling approach with the Engineering Masonry model (EMM) were conducted to replicate the experimental response. The model captured the global cyclic behavior of CM and LCM walls with reasonable accuracy, but it significantly underperformed for LM walls due to limitations in representing localized joint degradation. A shear modulus value of G=0.025E, calibrated through sensitivity analysis, yielded the best correlation with experimental data for CM and LCM walls, while G=0.4E worked well for LM walls. Numerical predictions of peak load deviated by 3.75% and 15.72% for high and low aspect ratio walls, respectively. Analytical formulations for lateral strength aligned well with test results. The findings emphasize the critical influence of mortar properties and aspect ratios in seismic behavior of URM walls and highlight the need for enhanced modeling approaches to predict the failure behavior of URM walls when both aspect ratio and mortar types are studied together.