Behavior of Retrofitted URM Walls under Simulated Earthquake Loading

TLDR

Unreinforced masonry buildings perform poorly under seismic forces and are the primary cause of loss of life in recent earthquakes, largely due to out‑of‑plane bending failures caused by lack of reinforcement. The study tested three half‑scale unreinforced brick walls retrofitted with vertical composite strips under cyclic out‑of‑plane loading, varying five reinforcement ratios and two glass‑fabric composite densities. The retrofitted walls supported lateral loads up to 32 times their weight, deflected up to 2 % of their height, and exhibited tensile‑failure or delamination depending on fabric density, demonstrating that composite strips provide a reliable, energy‑dissipating strengthening alternative.

Abstract

Unreinforced masonry (URM) buildings perform poorly under seismic forces and have been identified as the main cause of loss of life in recent earthquakes. Many of these structures fail in out-of-plane bending due to the lack of reinforcement. In this study, the experimental results from three half-scale unreinforced brick walls retrofitted with vertical composite strips are presented. The specimens were subjected to cyclic out-of-plane loading. Five reinforcement ratios and two different glass fabric composite densities were investigated. The mode of failure is controlled by tensile failure when wider and lighter composite fabrics are used and by delamination when stronger ones are used. The tested specimens were capable of supporting a lateral load up to 32 times the weight of the wall. A deflection as much as 2% of the wall height was measured. Although both URM walls and composite strips behave in a brittle manner, the combination resulted in a system capable of dissipating some energy. Retrofitting URM walls with composite strips proved to be a good and reliable strengthening alternative.