Tensile behaviour of concrete-filled double-skin steel tubular members

Concrete-filled double-skin steel tube (CFDST) a type of steel-concrete composite section which has two concentrically placed steel tubes and concrete filled in between. The CFDST members inherit the advantages of traditional concrete-filled steel tubes and are relatively lighter. They have been used in electric poles and have great potential in other types of structures. This paper in particular presents an experimental study on the concentrically and eccentrically loaded CFDST tensile members. The test parameters include the load eccentricity, the hollow ratio and the nominal steel ratio of the cross section. It is found that the filled concrete works efficiently with the double steel tubes, and provides additional support to the steel tubes under tension. All eccentrically loaded CFDST tensile members exhibit ductile behaviour with end rotation exceeding 0.1 rad. Design calculations are also assessed. The results indicate that the existing design proposal for CFDST tensile member has to be improved.