Seismic performance and analytical model of CFDST joint with endplates and long bolts

Developing the prefabricated structures is an effective way to reduce carbon emission. At present, the research on the prefabricated concrete-filled double-skin steel tubular (CFDST) joints is insufficient. In this paper, a prefabricated steel beam to CFDST column joint was proposed. In order to investigate the seismic behavior of the joint, a series of pseudo-static tests were performed on four 1/2 scale specimens with consideration of the endplate type and the inner steel tube shape. The failure modes included bending deformation of the endplate, warpage of the bolts, fracture of the weld seam, and buckling of the steel beam flange. Besides, all specimens exhibited better hysteretic behavior, ductility, strength, and stiffness. The ultimate strength and the energy dissipation capacity of the joint with the extended endplate were higher than the joint with the flush endplate. The inner steel tube shape had limited impact on the seismic performance except that the inner circular steel tube can distinctly increase the energy dissipation capacity of the extended endplate joint. According to the classification method in EC3, the proposed prefabricated joint was the semi-rigid and partial-strength joint. Moreover, the strain analysis indicated that the yield pattern was from the steel beam flange to the endplate. In addition, a prediction method of moment resistance was proposed and verified by test results. The research results of this paper provide a design basis for the prefabricated CFDST structures.