Shear performance of brick masonry walls strengthened by deep structural repointing using FRP reinforcement

Enhancing seismic safety of masonry structures while preserving historical authenticity requires specific retrofitting techniques. Bed-joint structural repointing has emerged as an attractive solution for heritage conservation. However, existing studies primarily focus on shallow embedment depths ($\le$ 30 mm) with divergent conclusions. In order to optimize the strengthening effect while considering the construction feasibility, this study innovatively increased the embedment depth to 80 mm to examine the shear performance of brick masonry walls strengthened by deep structural repointing with FRP reinforcement. Through diagonal compression tests, crack patterns, failure modes, shear stress-strain curves and related mechanical parameters were analysed under three variables: FRP reinforcement type, frequency of grooves and amount of reinforcement per groove. Experimental results revealed the near-surface mounted (NSM) FRP reinforcement significantly improved the post-peak performance of the masonry walls. Compared to unreinforced specimens, the shear strength increased by 6 %–67 %, ultimate strain by 54 %–444 %, ductility by 75 %–361 %, and energy dissipation capacity by 39 %–1113 %. These values highlighted the efficacy of structural repointing in deformation capacity improvement. The material property of FRP reinforcement had a minimal effect on shear performance improvement, while the geometric parameter exerted a greater influence. Instead of merely increasing the frequency of grooves, enhancing the reinforcement amount per groove proved to be a more effective strategy. Additionally, deep structural repointing mitigated out-of-plane failure risk by reducing eccentricity effects. Based on the experimental findings, predictive formulas for the shear capacity of masonry walls reinforced with NSM FRP were proposed, providing a reliable design basis for the application of FRP materials in historical building rehabilitation.