Effect of bidirectional load on seismic performance of jacketed external diaphragm joints of high-strength concrete-filled high-strength steel tube frame

Abstract

As one of the solutions for promoting green building and building industrialization, the application of high-strength concrete-filled high-strength steel tube (HCFHST) can further improve the structural performance of concrete-filled square steel tube (CFST). The beam-column joints, being a major stress component of the frame structure, influence the overall structure's performance during earthquake activity. In the external diaphragm joint of the frame, the stiffness of the steel tube at the connection between the external diaphragm and the CFST column is insufficient; aiming for this, a new type of jacketed external diaphragm joint (JED joint) connected between HCFHST column and steel beam were proposed in this paper. The ABAQUS was used to establish an analysis model to simulate the seismic performance of the joint accurately, and 5 kinds of bidirectional load conditions corresponding to the actual seismic action were designed to carry out numerical simulation for the evaluation of the seismic behavior of the joints of 17 specimens (4 groups), revealing the influence law of bidirectional load and providing design suggestions. The results showed that the hysteresis curve of the JED joint was full, the ductility coefficient was between 2.41 and 4.11, the equivalent viscous damping coefficient was between 0.48 and 0.6, and the deformation and energy consumption capacity in the joint domain reached the ductility requirements specified in GB 50011 and FEMA-350. According to AISC-LRFD and EC3, JED joints were determined to be semi-rigid. The seismic performance of the JED joint under bidirectional load was superior to that under unidirectional load. For the seismic performance of space joints, the most unfavorable load angle joint is characterized by bidirectional synchronous seismic action in the direction of 45°, edge joints are characterized by bidirectional asynchronous seismic action, and middle joints are manifested as constant load and unidirectional seismic joint action.