Bond Strength of FRP Rebar to Concrete: Effect of Concrete Confinement

According to ACT 440.1R-06, the presence of transverse reinforcement does not affect the bond strength of fiber reinforced polymer (FRP) rebar to concrete. This conclusion was based on a limited number of data (19 confined beam tests) available in literature at the time. In the present study, 177 beam bond test data, failed by concrete splitting, was collected to investigate the effect of concrete confinement on the bond strength with FRP rebar. Of these 177 beam-type specimens, 105 specimens had transverse reinforcement. It was observed that the presence of transverse reinforcement increased the bond strength of FRP rebar to concrete by 10%-15%, which eventually decreases the development length needed for attaining the tensile strength of FRP rebar. A linear regression was performed on the collected data to develop an equation to determine the bond strength of FRP rebar to concrete in presence of transverse reinforcement and the equation was compared with the ACT 440.1R-06 equation and the experimental results. Based on the analysis, it was found that the proposed equation is in good agreement with the experimental results and it yields a better estimate of bond strength than the ACI 440.1R-06 equation.