Experimental studies on seismic performance of square concrete-filled steel tubular column to U-shaped steel-concrete composite beam joints under cyclic loading

To study the seismic performance of square concrete-filled steel tubular (CFST) column to U-shaped steel concrete composite beam joints, cyclic loading test was carried out on two interior joints and two exterior joints with a scale ratio of 3/4. The parameters were welding details in panel zone and axial load level. The ductility, load-carrying capacity, stiffness and strength degradation, and energy dissipation capacity were further analyzed according to the failure mode, hysteretic and skeleton curves of the specimens. Test results show that the typical failure modes are the local buckling of the lower flange and web of the U-shaped steel-concrete composite beam, the collapse of the slab, and the fracture of the channel steel in the panel zone. The hysteretic curves of the specimens are in plump-shape. The displacement ductility ratio equals 2.1-3.3, elastic limit of inter-story drift rotation equals 1/71-1/54, elastic-plastic limit of inter-story drift rotation equals 1/30-1/16, and the equivalent viscous damping coefficient equals 0.15-0.21, indicating that the specimens show good deformation and energy dissipation capacities. The axial load level has little effect on the energy dissipation capacity and load-carrying capacity of specimens, and the specimen without welding in the intersection of the channel steel shows better deformation capacity, but the load-carrying capacity is markedly reduced. In addition, the load-carrying capacity and total energy dissipation of interior joints are significantly higher than those of the exterior ones. © 2021, Editorial Office of Journal of Building Structures. All right reserved.