Seismic performance of special-shaped concrete-filled steel tubular column to U-shaped concrete-filled steel beam joints under cyclic loading

To study the failure modes and seismic performance of the joints of special-shaped concrete-filled steel tubular column to U-shaped steel-concrete composite beam, three full-scale exterior joints were tested under reversed low cyclic loading. The test parameters were the details of panel zone and axial compression ratio. The mechanical process and failure modes of the specimens were investigated, as well as the seismic performance, such as load-displacement hysteretic curve, bearing capacity, stiffness and strength degradation behaviors, energy dissipation capacity and ductility were also analyzed. The test results show that the typical failure modes were the buckling of the steel tube wall, the fracture of the connecting channel steel, and the collapse of the floor concrete. The hysteretic loops of the joints are in plump-shape. The story displacement ductility ratio μ is 1.43-2.02, the elastic limits of story drift rotation θy is 1/62-1/48, elastic-plastic limits of story drift rotation θu is 1/39-1/30, and the equivalent viscous damping coefficient ξeq is 0.140-0.170 indicate that the joint has favorable deforming capacity and a certain energy dissipating capacities. In addition, the reinforcements passing through the panel zone can improve the bearing capacity and stiffness of the joint subject to the forward loading, and the improvement of the axial compression ratio can also improve the energy dissipation capacity. © 2020, Editorial Office of Journal of Building Structures. All right reserved.