Cyclic Loading Test for Concrete-Filled U-Shaped Steel Beam to Concrete-Filled Steel Tube Column Connections

Concrete-filled U-shaped steel (CFUS) beam and concrete-filled steel tube (CFST) column are recently developed because of the quick construction and economical saving. This paper aims to investigate the seismic performance of a composite connection system connecting CFUS beam to square CFST columns. In the joint system, the grooved cuts on the square tube allowed the U-shaped steel beam passing through the joint core completely, which developed a through beam connection. To verify the seismic behavior of the beam-column connection, three specimens designed according to the strong column-weak beam and strong joint-weak member seismic concept were tested under combined constant axial compression and cyclic loading. For the test parameters, the different connection details and the axial load on the CFST column were considered. The test results showed that the specimens exhibited good load-carrying, deformation, and energy dissipation capacities. The maximum story drift ratio of all the three specimens was 5%, satisfying the minimum requirement of special moment frames. The primary failure mode of the specimens was local buckling of the webs and the fracture of the bottom flanges of the CFUS beam near the column tube. In addition, the joint shear strength of the specimens was evaluated based on ASCE design guidelines.