Numerical Investigation of the Seismic Performance of Deficient Reinforced Concrete Beam–Column Joints Strengthened With CFRP Sheets

Shear failure of reinforced concrete (RC) beam–column joints is a primary cause of structural collapse in moment‐resisting frames subjected to seismic loading, particularly in older or poorly detailed buildings. This study presents a comprehensive three‐dimensional nonlinear finite element (FE) investigation into the cyclic behavior of exterior RC beam–column joints strengthened with carbon fiber–reinforced polymer (CFRP) sheets. Numerical models were developed in ANSYS to simulate both unstrengthened and CFRP‐retrofitted joints, incorporating typical deficiencies such as insufficient joint shear reinforcement and reduced concrete strength in the joint core. The proposed modeling approach was validated against published experimental results and demonstrated good agreement in terms of load–deformation response, stiffness degradation, energy dissipation, and failure mechanisms. Parametric analyses were then conducted to evaluate the effectiveness of various CFRP strengthening configurations. The results indicate that CFRP retrofitting significantly enhances joint strength, ductility, and energy dissipation while effectively preventing brittle joint shear failure. Strengthened specimens exhibited stable hysteretic behavior and promoted plastic hinge formation in the beam rather than within the joint core, resulting in a safer and more ductile seismic response. The findings confirm that appropriately detailed CFRP strengthening schemes provide an efficient and practical retrofit solution for improving the seismic performance of deficient RC beam–column joints.