Full-range behavior of FRP-to-concrete bonded joints subjected to combined effects of loading and temperature variation

Abstract

Concrete structures strengthened with externally bonded fiber-reinforced polymer (FRP) composites are likely to experience significant temperature variations (i.e., thermal loadings) due to daily and seasonal temperature changes or possible fire exposure during service life. Such thermal loadings may lead to changes in the mechanical properties of components (including FRP, bonding adhesive and concrete substrate) and induce interfacial thermal stress due to the thermal incompatibility between FRP and concrete. A limited bond length is usually adopted to investigate the bond behavior (e.g., the local bond-slip characteristics) of the FRP-to-concrete interface under temperature variations. This paper presents an analytical study for the first time to predict the full-range deformation behavior of a mechanically loaded FRP-to-concrete bonded joint with a limited bond length under temperature variations. The solution is in a closed-form manner and has enabled isolation of the interfacial thermal stress effect from the temperature-induced changes of material properties, thereby leading to an accurate calibration of the bond-slip characteristics and the interfacial fracture energy. The closed-form analytical solution has been verified by comparing the analytical predictions with the existing experimental and numerical results in the literature. To further understand the mechanism of the FRP-to-concrete interface under combined thermal and mechanical loadings, the effects of thermal stress and bond length on the interfacial responses and the full-range deformation behavior of the FRP-to-concrete interface are comprehensibly analyzed.