Nonlinear Seismic Response of Strengthened Reinforced Concrete Frames: A Comparative Finite Element Investigation Using CFRP, RC Jacketing, and UHPC

Abstract

This study investigates the seismic performance of reinforced concrete (RC) frames strengthened using different retrofitting techniques under cyclic loading conditions through advanced finite element simulation. A three-dimensional nonlinear finite element model was developed in ABAQUS and calibrated using the experimental results of a previously tested RC frame reported in the literature. Concrete behavior was simulated using the Concrete Damage Plasticity (CDP) model, while reinforcing steel was modeled using an elastoplastic constitutive relationship. The numerical model achieved a high level of agreement with the experimental response, with an accuracy of approximately 95.12% in predicting the peak lateral load, as well as accurately capturing stiffness degradation, crack propagation, and hysteretic behavior. Following validation, three strengthening techniques were investigated, including CFRP strengthening, RC jacketing, and UHPC jacketing. The results demonstrated that all strengthening methods enhanced the seismic behavior of the frame; however, UHPC strengthening exhibited the best overall performance, achieving an increase of approximately 88.5% in load-carrying capacity, 44.73% in ductility, and significant improvement in stiffness and energy dissipation capacity. The findings confirm the effectiveness of advanced strengthening techniques, particularly UHPC jacketing, in improving the seismic resistance and structural performance of deficient RC frames. Keywords: Reinforced Concrete Frames, Seismic Strengthening, Cyclic Loading, Nonlinear Finite Element Analysis, ABAQUS, CFRP, RC Jacketing, UHPC