RC beams shear-strengthened with FRP : shear resistance contributed by FRP

Abstract

In determining the shear strength of reinforced concrete (RC) beams shear-strengthened with externally bonded fibre-reinforced polymer (FRP) reinforcement, the evaluation of the shear resistance contributed by the FRP reinforcement is the key issue. When the FRP reinforcement is in the form of U-jackets or side strips, debonding of the FRP reinforcement from the concrete substrate generally governs the shear strength of the beam and the evaluation of the shear resistance from the FRP becomes more challenging. In this paper, a theoretical shear strength model in closed-form expressions modified from a model proposed by Chen and Teng for shear debonding failure is first presented. A computational model that captures the debonding process more accurately than the closed-form theoretical model is then described. Predictions from both the original model of Chen and Teng and the modified theoretical model are then compared with results from the computational model. These numerical comparisons show that Chen and Teng's original model provides closer predictions for the shear resistance contributed by FRP side strips, but the modified theoretical model generally leads to slightly more accurate predictions for FRP U-jackets. The reasons behind this are explained. The original model of Chen and Teng is recommended as the more suitable model for use in design, given its overall accuracy and simpler form.