Seismic Behavior of Reinforced Concrete Beam-Column Joints Strengthened with Varied Installation Length of CFRP Sheets

The beam-column joint is an important part of reinforced concrete structures and significantly impacts the structure’s overall performance. Increasing the capacity of beam-column joints is needed, especially in joints lacking stirrup reinforcement. This research evaluates the effect of installation length on the seismic behavior of beam-column joints without stirrup at the joints, which are strengthened with Carbon Fiber Reinforced Polymers (CFRP) sheets. Six interior beam-column joints subjected to cyclic load were tested, with two as controls and four others strengthened with two side CFRP sheets. The behavior of joints was observed by analyzing load-displacement relationships, envelope curves, crack patterns, failure mechanisms, energy dissipation, stiffness degradation, and ductility in detail. The finite element method numerically determined the crack patterns and load-displacement relationships. The results indicate that installing CFRP with a length equivalent to twice the beam height significantly enhances seismic performance and shear behavior, providing a practical solution for retrofitting non-ductile structures.