Theoretical analysis on full torsional behavior of RC beams strengthened with FRP materials

An analytical model is developed to predict the full torsional behavior of reinforced concrete (RC) beams externally wrapped with fiber reinforced polymer (FRP) materials. Based on previous modified softened truss model for torsion (MSTMT), the proposed model additionally considers the effect of concrete in tension to make a better prediction for the full torsional behavior. Reasonable compressive and tensile constitutive relationships of FRP strengthened concrete under torsion are employed in the proposed model, MSTMT-FRP-tension. Then an efficient solution algorithm is developed to accomplish the theoretical analysis. To verify the newly proposed model, a comparative analysis is conducted between the theoretical predicted torque-twist curves and the reported experimental ones of solid rectangular section strengthened with carbon fiber reinforced polymer (CFRP) or glass fiber reinforced polymer (GFRP) materials. The good agreement between the comparative results indicates the validity of the analytical model for predicting the torsional behavior of RC beams strengthened with FRP materials both at the pre-cracking and post-cracking stage.