Experimental study on seismic performance of precast high-strength RC beam-column joint with embedded channel steel and UHPC

To further improve the seismic performance, economic and seismic resilience of prefabricated reinforced concrete (RC) beam-column joints, an innovative prefabricated high-strength RC beam-column joint (PHBCJ) with ultra-high strength concrete (UHPC) and embedded channel steel has been developed, which integrates the 500 MPa high-strength rebar, 120 MPa UHPC and embedded channel steel (ECS). To evaluate its performance, one high-strength cast-in-place RC beam-column joint and four PHBCJ specimens with varying rebar strength, concrete strength and ECS, along with two repaired PHBCJ specimens, were tested under cyclic loading, simulating rare and ultimate seismic conditions. Finite element models were established and verified with test results. Key parameters such as failure modes, hysteresis curves, skeleton curves, secant stiffness, energy dissipation capacity and strain-displacement behavior were analyzed. The results indicate that the incorporating UHPC and ECS effectively prevents cracking occurs in the joint region, confining damage primarily to the beam ends. The PHBCJ with HRB500 rebar and ECS demonstrated superior bearing capacity and cost efficiency. Moreover, the seismic performance of PHBCJs with grouted sleeve connections between the precast upper and lower columns, combined with post-poured concrete in the joint region, closely resembled that of cast-in-place specimen. Additionally, the repaired joints exhibited nearly identical seismic performance to their pre-damage condition. In the PHBCJ with post-pored UHPC, damage was localized at the end of beam, reducing the affected area and severity, thereby enhancing repair efficiency and economic viability. Overall, the novel PHBCJ successfully meets the key design principles, including “strong joint weak component,” “strong column weak beam,” “strong shear weak bending,” and “plastic hinge relocation away from the column,” ensuring improved seismic performance and seismic resilience capacity, which align well with the seismic demands of modern structures.