Seismic performance of prefabricated joints for T-shaped CFST column to U-shaped steel composite beam

The combination of T-shaped concrete-filled steel tubular (CFST) columns and U-shaped steel-concrete composite beams is widely acknowledged for its superior mechanical properties, efficient prefabricated construction, and optimized building space utilization, presenting broad application prospects in prefabricated structural systems. As the critical load-transferring components and potential seismic vulnerable links of such structures, the beam-column joints between these two members deserve in-depth systematic research. This study innovatively proposes two types of prefabricated corbel connection joints with a fully bolted configuration and a bolt-welded hybrid configuration, respectively. Full-scale quasi-static seismic tests and finite element (FE) simulations were carried out on both joint types, and a theoretical calculation formula for the bearing capacity of the joints was developed. The results indicate that both proposed joints exhibit higher ductility coefficients than conventional reinforced concrete joints, with their positive bearing capacity exceeding the negative counterpart. The fully bolted joint shows superior ductility over the bolt-welded hybrid joint, albeit with a notable reduction in bearing capacity. A plastic hinge forms at the beam end for the fully bolted joint, which maintains favorable deformation capacity after the peak load; by contrast, the bolt-welded hybrid joint develops a plastic hinge at the corbel base, with failure accompanied by tearing along the column wall. The bearing capacity calculation formulas can accurately predict the mechanical performance of the proposed joints.