Analytical Model for Predicting Shear Strengths of FRP-Retrofitted Exterior Reinforced Concrete Beam-Column Joints

In this study a nonlinear procedure for analysis of a membrane element of a FRP strengthened concrete beam-column joint is proposed based on softened truss model. The procedure employs three equations for equilibrium, three for compatibility and six equations for the constitutive laws of materials. The model is capable of analysing nonlinear behaviour of RC beam-column joints under cyclic loading and has three major attributes including nonlinear association of stress and strain in the presence of FRP, contribution of concrete damage by means of softening coefficient and consideration of the bond effect between steel, FRP and concrete. The proposed model is applied to some previously tested, strengthened beam-column joints and shows good predictions of shear strength of these joints. The effect of various parameters on response of reinforced concrete beam-column joint, such as column axial load, FRP reinforcement amount and FRP properties has been studied on parametric manner. It is observed that even a low quantity of FRP can enhance the shear capacity of the joint significantly. Also, it is observed that the axial load increases the confinement of the joint care, which in turn increases the shear capacity of the joint.