Seismic performance of a novel concrete-filled steel tube column to continuous reinforced concrete beam joint with multiple openings in the core region

This study developed a novel concrete-filled steel tube column to continuous reinforced concrete beam joint with multiple openings in the core region, aiming to eliminate field welding and improve construction efficiency. To evaluate the seismic performance of the joint, six full-scale specimens were tested under cyclic loading, which and a series of numerical simulations were implemented upon refined models. The effects of reinforcement ratio, steel tube thickness, and concrete strength on the failure mode and the mechanical performance degradation of the joint were quantitively evaluated. The results indicated that depending on the beam-column flexural capacity ratio, three typical failure modes, i.e., compression bending failure at the column end, shear failure at the joint core region, and flexural failure at the beam plastic hinge region, were observed. Among them, the flexural failure-dominated joint possessed the best energy dissipation capacity and a high ductility coefficient greater than 3.72. Moreover, increasing the thickness of steel tube within the core region can effectively compensate for the reduction of seismic performance caused by multiple openings, and a preliminary value of at least 2.5 times the thickness of column steel tube is recommended. This novel joint configuration exemplifies a balance between structural integrity, construction efficiency, and mechanical performance, rendering it a feasible alternative for frame structure in seismic-prone regions.