Seismic behavior of joint of top-flange-welded and bottom-flange-bolted with CFDST column to steel beam

In order to investigate the seismic behavior of the composite joints of top-flange-welded and bottom-flange-bolted with concrete-filled double steel tubular (CFDST) column to steel beam,five scale 1∶ 2. 4 joints were tested under low-cyclic loading. The failure characteristics, hysteresis curves, skeleton curves, ductility, rigidity and bearing capacity, energy dissipation, and other seismic performance indicators of the specimens were analyzed. A plastic analysis model of the composite joints was established based on the test failure modes. The bending capacity formula of the joints was derived, which was validated with the experimental results in this study and relevant literatures. The results show that beam end failure occurres in the joint specimens, exhibition as fracture or wavy plastic deformation at the connection of the upper flange of the steel beam to the ring plate, vertical slip of the web of the steel beam and the connection plate, and horizontal slip at the bolt connection of the lower ring plate. The hysteresis curve of the specimens is stable and full without pinching. The ductility coefficients and the equivalent viscous damping coefficients range from 2. 88-4. 60 and 0. 472-0. 579, respectively. The joint area has an excellent capacity for deformation and energy dissipation. The types of composite joints are semi-rigid joints. The stiffness, bearing capacity, ductility, energy dissipation capacity and other seismic performance indicators of the joint are improved by increasing the thickness, width, and extension length of the outer ring plate and the bolt numbers in the bottom ring plate. The results of the theory calculation and experiment reach a good agreement, which shows the calculation method of the flexural bearing capacity for composite joint proposed in this paper has good precision. © 2024 Science Press. All rights reserved.