Flexural Behavior Of Composite Concrete-Filled Steel Tube Roof Structure Under Symmetrical Concentrated Loads

This paper presents an experimental research on the composite concrete-filled steel tube roof (C-CFST-R) structure, which is proposed as a new type of tubular-roof structure. The longitudinal large-diameter steel tubes are connected by small-diameter steel tubes in transverse, forming the supporting structure after concrete casting. The mechanical performance and failure mode of the C-CFST-R members are analyzed and following parameters are tested: diameter of the connection tube, eccentricity of the connection tube, the presence of bottom steel plate, and the longitudinal tube spacing. A theoretical formulation for the transverse bending capacity of the cross-section of this structure is also presented. The results show that the failure mode of the test specimens exhibits ductile failure. The transverse stiffness and the bearing capacity increase with the increase of connection tube diameter, while the eccentricity of connection tube has unobvious impact on flexural behavior of the member. Welding the bottom steel plate significantly enhances the bending stiffness and capacity by more than 4 times. The increase of longitudinal tube spacing mainly causes reduction in transverse stiffness. The proposed theoretical calculation method shows a reasonable prediction of the bending capacity in compare with the test results.