Behavior of concrete-filled double-skin thin-walled steel tubular columns under eccentric compression

In order to investigate the effects of the eccentricity and slenderness ratio on the behaviors of concrete-filled double-skin steel tubular columns with the outer stiffened thin-walled steel tube, the tests of five slender concrete-filled double-skin thin-walled steel tubular (CFDSTST) columns with outer square hollow section and inner circular hollow section under the eccentric compression were carried out. The test results indicate that the load-carrying capacity decreases with the increase of the eccentricity and slenderness ratio. The ductility of this composite column is lower than traditional CFDST columns. The finite element (FE) simulation of CFDTST columns under eccentric compression was performed. The FE predictions agreed well with the test results. Based on the FE model, the mechanical and parametric analyses were carried out. The mechanical analysis indicates that the confinement of the outer steel tube is focused on a small region at the corner of the cross-section. And the most of the loading is carried by the core concrete. The parametric analysis indicates that the shape of the axial compression versus moment interaction curve is directly affected by the concrete strength, steel yield strength, diameter to thickness ratio, diameter to width ratio or slenderness ratio. A simplified calculation method was proposed to predict the load-carrying capacities of CFDTST columns under eccentric compression, and it is useful for real project. © 2018, Editorial Office of Journal of Building Structures. All right reserved.