Mechanical behaviour of concrete-filled double-skin steel tube (CFDST) with stiffeners under axial and eccentric loading

This paper presents an experimental investigation of the mechanical behaviour and working mechanism of the concrete-filled double-skin steel tube (CFDST) with stiffeners. A total of 40 CFDST columns were prepared and subjected to axial and eccentric loading. The failure modes and ultimate load-bearing capacities, together with the deformation and strain responses of the specimens, were analysed. The effects of the stiffener type, slenderness ratio, and eccentricity ratio were researched in this study. The test results indicated that the ductility of the CFDST specimens was improved greatly by the presence of stiffeners, which gave a lower load-bearing capacity owing to the reduction in the effective area of the inner concrete. Moreover, an analytical-numerical model was developed to analyse the mechanical behaviour of the CFDST specimen, and an improving mechanism was considered. In addition, theoretical estimations to predict the ultimate load-bearing capacities of CFDST specimens subjected to axial and eccentric loading were established. These estimations showed good agreement with the theoretical results and the test results.