Numerical study of seismic performance of unreinforced masonry walls retrofitted by reinforced concrete layers under in-plane cyclic loading

Masonry structures have been a large part of the built environment for centuries, yet they remain highly vulnerable to seismic actions. Recent earthquakes have emphasized the need for reliable assessment methods and effective strengthening strategies. This paper presents a numerical investigation of unreinforced masonry (URM) walls retrofitted with reinforced concrete (RC) layers and subjected to in-plane cyclic loading. Three wall configurations were analyzed: a reference URM wall without retrofitting, a wall retrofitted with a 60 mm RC layer on one side, and a wall retrofitted with two 30 mm RC layers on both sides. The seismic performance was evaluated using key indicators, including global capacity curve, ductility factor, stiffness degradation, and energy dissipation. The results show that RC retrofitting significantly enhances the seismic response of URM walls, improving load capacity, crack distribution, ductility, and energy dissipation. Among the studied configurations, the double-sided retrofitted wall achieved the best overall performance, highlighting the effectiveness of symmetric RC layers in reducing seismic vulnerability.