Analytical study on RC beams strengthened for flexure with externally bonded FRP reinforcement

This paper presents analytical study on reinforced concrete (RC) beams strengthened for flexure with externally bonded fiber reinforced polymer (FRP) reinforcement. A simple yet rational numerical model is developed and proposed for this purpose. The model is based on cross-sectional analysis satisfying strain compatibility and equilibrium conditions. The moment-curvature relationship can be generated for an RC beam section using an incremental strain technique. The model can also generate the load-deflection relationship of the beam with respect to its configuration, loading system, and preloading conditions. The model can predict the flexural capacity of FRP-strengthened section based on full composite action and IC debonding failure modes. This also allows for designing the FRP strengthening area according to the desired failure mode. Various IC debonding criteria were adopted in the model and compared with test results from the literature. The result of comparison indicated that the accuracy of the model is dependent on the adopted IC debonding criterion. Furthermore, the model was verified against test data related to full composite action failure mode and good agreement was found.