Strengthening a RC Beam Under Torsion: An Experimental-Numerical Study

This paper shows the effect of fibre-reinforced polymer strengthening on the behaviour of reinforced concrete beams under pure torsion. Two RC beams of 150mm× 250mm× 1500mm were cast monolithically with lever arms and tested. To shed light on shear strengthening without the intervention of shear stirrups, 0% shear reinforcement and 0.69% longitudinal reinforcement were used to reinforce the beam. Firstly, experimental tests were carried out. After that, we performed a numerical validation of the experimental beams, and then a nonlinear finite element model was developed for further study. Adopting a strengthening program with two different parameters, the number of strengthened faces and the number of layers, in order to strengthen the beam. The experimental part illustrated the shear crack initiation was always on the wider face of the beam. In the failure of a beam under torsion, a crack needs to propagate on at least three faces. Extensive numerical analysis shows an increase of the ductility represented by twist-angle in addition to the strength. The gain in torque resistance and twisting angle was found to be 54.08% and 1763%, respectively.