Seismic Behavior and Design of Concrete-Filled Thin-Walled Steel Tube Column-to-Foundation Connections

AbstractThin-walled steel tubes are highly recommended to be used in concrete-filled steel tube (CFST) columns due to their economic benefits. However, the inherent difficulty of connections between the steel tube and foundation limits the application of thin-walled CFSTs. Four types of CFST column-to-foundation connections employing anchor bars to resist the bending moment are proposed, avoiding the insertion of the steel tube into the foundation. In this paper, the design method for the proposed column-to-foundation connections was first studied. Eight column-to-foundation connections for thin-walled CFST columns were tested under combined constant axial load and cyclic lateral load. The observed failure modes, load-displacement hysteresis curves, load-displacement skeleton curves, circumferential stiffness, energy-dissipation coefficient, and load-strain curves of steel tube were analyzed and presented. The experimental results and theoretical analyses indicated that properly designed connections possessed higher bending strength and better ductility than traditional embedded connections.