Modeling of Reinforced Concrete Beam–Column Joint Retrofitting

Abstract

Failure of reinforced concrete (RC) beam–column joints (BCJs) is sudden especially when they are subjected to high shear demands caused by seismic actions. One novel advantageous method is shear retrofitting of BCJs with carbon fiber-reinforced polymer (CFRP) using an externally bonding technique. CFRP is a lightweight, high strength, flexible, and corrosion-resistant material, and the proposed system is highly efficient and exhibits high shear capacities compared to other retrofitting methods such as concrete and steel jacketing. A recent experimental study on retrofitting of reinforced concrete BCJs using composites shows that the CFRP retrofitting configurations significantly improved the behavior of deficient joints. Strengthened specimens exhibited significant increases in strength and energy dissipation capacities as compared to the unstrengthened control specimen. The lateral load capacities of strengthened specimens increased by 50–100% when compared to the control specimen. Cracks propagated diagonally from one corner to the other corner of the joint. Therefore, CFRP fibers were oriented diagonally closer to principal stresses to prevent shear cracks in the joint core. The anchorages were applied to the beam, preventing the debonding of the CFRP sheets which gave a superior retrofitting effect. However, in the context of RC, shear behavior is still a riddle, exploring shear strengthening optimization as a challenge. The current study verifies the nonlinear numerical simulation potential of beam–column joint retrofitting using the experimental database. CFRP thickness is identified as a governing strengthening parameter via the FE analyses. The failure load increases with the increase of CFRP thickness, but the change in the ultimate load is not proportional to the increment of the thickness of the CFRP material.