Structural performance of reinforced concrete interior beam-column joints with high-strength bars

This study evaluates the structural performance of reinforced concrete interior beam-column joints having high-strength screw-type steel bars mechanically connected with couplers. A total of six full-scale specimens were cast and subjected to repeated cyclic lateral loads. High-strength screw-type reinforcing bars, with a yield strength of 690 MPa, were used as longitudinal reinforcement of the specimens. The main test variables were designed with and without couplers and the longitudinal reinforcement ratio of the beam. The couplers were applied to the plastic hinge zones of columns and beams to maximize their impact. The experiment confirmed that the flexural cracks generated near the couplers slightly influenced the initial stiffness, the yielding point of the longitudinal reinforcement of the beams, and the displacement at peak load of the specimens. However, the load versus story drift relationship, the peak load, and the ductility capacity of the specimens were not significantly affected. In addition, the analytical results obtained using the current structural design codes and finite element analysis were similar to the experimental results.