Bond Behavior of the ETS FRP Bar Shear-Strengthening Method

The embedded through-section (ETS) technique was recently developed to avoid the debonding failure that occurs with other fiber-reinforced polymer (FRP) strengthening techniques, such as the externally bonded (EB) and near-surface-mounted (NSM) methods. The method offers greater confinement and leads, therefore, to a substantial improvement in bond performance. In addition, it requires less concrete preparation than the EB strengthening technique. In this study, experimental results from 13 direct-shear test specimens are reported. The influence of the following major parameters on the bond behavior of FRP-strengthened reinforced concrete beams is examined: concrete strength, hole diameter, bar diameter, bar surface area, and bar bond length. The experimental results show that debonding can be avoided by providing a sufficient bar length and high concrete strength. Among the analytical models suggested in the literature for the bond behavior of FRP reinforced concrete, the Eligehausen, Popov, and Bertero (BPE) modified model and the Cosenza, Manfredi, and Realfonzo (CMR) model are compared with the experimental results obtained here. The CMR model with new fitting parameters is found to be an accurate way of simulating the experimental results. A new equation that accounts for concrete compressive strength and bar diameter is provided to estimate the development length. DOI: 10.1061/(ASCE)CC.1943-5614.0000280. (C) 2012 American Society of Civil Engineers.