Flexural Performance of Reinforced Concrete Beams Strengthened with Carbon Fiber-Reinforced Polymer (CFRP) under Hygrothermal Environment Considering the Influence of CFRP-Concrete Interface

As an important component, the bond behavior of carbon fiber-reinforced polymer (CFRP)-concrete interface for a reinforced concrete (RC) beam is very significant. In this study, a theoretical model was established to analyze the flexural behavior of CFRP-strengthened RC beams, and the CFRP-concrete interfacial bond-slip relationship under hygrothermal environment was unified into one model. Two failure criteria corresponding to two types of failure modes, i.e., concrete crushing and intermediate crack (IC)-induced debonding, were developed. Through the theoretical model, the flexural behavior of deflection, interfacial shear stress distribution and ultimate load of a CFRP-strengthened RC beam under hygrothermal environment were obtained and predicted. Moreover, the theoretical model was verified by test results. The results showed that the hygrothermal environment had a significant impact on the CFRP-concrete interface behavior. Compared with the control beam without hygrothermal environment pretreatment, the deflection and ultimate load of the strengthened RC beam decreased by 51.9% and 20%, respectively.