Strengthening of Drilled Beam Column Connection with Openings

The integration of openings in reinforced concrete (RC) beam–column joints is a common practice for accommodating utility services, but these modifications can compromise structural integrity, especially under cyclic loading conditions. This study investigates the impact of post-construction openings on the performance of beam–column joints using a three-dimensional nonlinear finite element model developed in ANSYS. The model was validated against experimental data, demonstrating an error margin of less than 5.8%, confirming its accuracy. Two retrofit strategies, steel tube reinforcement and fiber-reinforced polymer (FRP) wrapping, were evaluated for their effectiveness in restoring the load-carrying capacity, stiffness, and energy dissipation of joints with openings. The results indicate that both retrofits improve performance; however, the steel tube retrofit outperforms the FRP wrap, maintaining higher load resistance at the 3% drift ratio, though cracks were observed in the surrounding concrete. While the FRP wrap shows similar peak load capacity, it exhibited reduced stiffness under larger cyclic deformations.