Seismic performance of concrete-filled steel tubular column connections using blind bolts

In this study, a demountable connection that connects the upper and lower concrete-filled steel tubular columns with an inner sleeve section and blind bolts (referred to as Hollo-Bolts in this study) is proposed. The utilization of Hollo-Bolts allows them to be installed outside the steel tubes prior to the concrete casting and renders such connection to be readily dismantled after typical service loading. In order to study the seismic performance of the concrete-filled steel tubular column-column connection, six specimens were designed in the present study. The studied parameters included the axial load ratio, length of the inner sleeve, and location of the connection. The results demonstrated that the proposed connection exhibited good ductility performance, and the disassembly and reassembly of the connection after a service loading had no significant effect on their seismic performance. Additionally, the load-transfer mechanism of the concrete-filled steel tubular column-column connection was explored. Simplified formulae of anti-slip flexural bearing capacity of the connection were proposed, and the predicted values agreed well with the test results on the safe side.