Analytical Study on the Torsional Behavior of Reinforced Concrete Beams Strengthened with FRCM Composite

In this study, an analytical approach was used to predict the full torsional response of RC beams strengthened with externally bonded fiber-reinforced cementitious matrix (FRCM) composite. The analytical model was based on the softened membrane model for torsion (SMMT) modified for fiber-reinforced polymer (FRP)-strengthened beams. As a first attempt, fully wrapped beams with fiber rupture governing the mode of failure were considered in this study. The model was validated by comparing the analytical response to the experimental response of five solid, rectangular RC beams. The model was able to predict values of the cracking and ultimate torsional moment and the corresponding angles of twist per unit length with reasonable accuracy. Also, reasonable agreement was achieved between the experimental and analytical results in terms of the overall response and failure sequence. The results confirm the feasibility of the SMMT model to predict the torsional response of fully wrapped FRCM-strengthened beams with the fiber rupture failure mode. However, additional modifications are required to extend the model to U-wrapped configurations and composite debonding failure modes.