Interfacial Bond Behavior and Load-Transfer Characteristics of CFRP-Strengthened Traditional Masonry with Glutinous Rice Mortar.

Traditional brick masonry buildings in China are commonly constructed using fired clay grey bricks bonded with glutinous rice mortar, forming a unique historical masonry system with significant cultural value. During long-term service, these structures are vulnerable to environmental deterioration, material aging, and seismic actions, resulting in cracking, deformation, and degradation of structural integrity and load-carrying capacity. Carbon fiber-reinforced polymer (CFRP) sheets have been increasingly applied for strengthening masonry structures due to their high strength-to-weight ratio, corrosion resistance, and convenient installation. However, most existing studies on Fiber-reinforced polymer (FRP)-masonry interfaces have focused on conventional masonry systems, while the interfacial bond behavior and load-transfer characteristics between CFRP sheets and traditional grey brick masonry bonded with glutinous rice mortar remain insufficiently investigated. This study investigates the interfacial bond behavior of CFRP-strengthened traditional grey brick masonry through combined experimental testing and numerical analysis. First, uniaxial compression tests were conducted to determine the mechanical properties of glutinous rice mortar and fired clay grey bricks. Subsequently, double-shear tests considering different CFRP bond widths, bond lengths, and interface integrity conditions were performed to characterize the failure modes, force-displacement responses, and interfacial load-carrying behavior. The effects of interface geometric and integrity conditions were considered to evaluate the load-transfer characteristics of the strengthened interface. Based on the experimental results, a finite element model considering interface behavior was established and verified through comparison with the experimental results, which was subsequently employed to investigate the influence of bond width on interfacial stress transfer behavior beyond the experimental conditions. The results show that interfacial debonding accompanied by near-surface masonry damage dominates the failure process of CFRP-glutinous rice mortar masonry interfaces. Increasing the CFRP bond width enhances the interfacial load-carrying capacity and initial stiffness, while the ultimate capacity exhibits an approximately linear relationship with bond width within the investigated range. Numerical analyses further demonstrate that increasing bond width expands the effective load-transfer region, redistributes interfacial stresses, and delays stiffness degradation. These findings improve the understanding of interfacial bond behavior and load-transfer characteristics in CFRP-strengthened traditional masonry systems and provide references for the design and performance evaluation of strengthening applications in historic masonry structures.