Development of multi-fiber approach finite element model for reinforced concrete beam using frp reinforcements under pure torsion

Abstract

A finite element model using a multi-fiber approach is proposed in this paper for the analysis of reinforced concrete (RC) members using fiber-reinforced polymer (FRP) reinforcements, with a specific focus on the effect of pure torsion. The proposed model is formulated using a displacement-based approach and a kinematic assumption involving a two-node Timoshenko beam. The compatibility and equilibrium between concrete and FRP materials in the membrane elements are formulated based on a discretization of the cross-section into several areas following its stress state and the principle of the Modified Compression Field Theory. The nonlinear responses of RC elements with FRP bars can be predicted using an appropriate constitutive material law with internal equilibrium of transverse reinforcement and concrete. The pure torsional response is implemented using an enhanced formulation of concrete's tensile behavior, which is based on experimental tests on torsion and the characteristics of FRP materials. The good agreement between the numerical results and experimental data confirms the validity of the proposed model