Compressive behaviour and design of tapered lightweight concrete-filled double-skin stiffened steel tubular short columns with large hollow ratio

Tapered concrete-filled double-skin steel tubular (CFDST) members, due to their high strength-to-weight ratio and inherent spatial advantages, hold significant prospect in marine structures, such as ocean platforms and wind turbine tower. As the height and span of the column continue to increase, its weight and local buckling problems begin to emerge and become the main concerns of engineering design. To address this issue, lightweight concrete instead of normal concrete and tapered steel tubes with longitudinal stiffeners are adopted. As a result, a novel composite member, called tapered lightweight concrete-filled double-skin stiffened steel tubular short columns with large hollow ratio (LHRTL-CFDSST), is developed by the authors. In order to gain a more comprehensive understanding of the axial compression behavior of LHRTL-CFDSST members and provide an axial strength model, this study conducted axial compression tests on ten LHRTL-CFDSST short columns, investigating key parameters such as hollow ratio, longitudinal stiffeners and diameter-to-thickness ratio. The results indicated that both larger hollow ratio sections and diameter-to-thickness ratios tend to reduce the axial compressive strength and the ductility of such members, while the effect of the longitudinal stiffeners are opposite. Based on the test results, finite element (FE) model was developed and validated, and was then to conduct the mechanical analysis of the studied members, followed by a parametric study. Finally, a novel method for predicting the axial compressive strength of LHRTL-CFDSST short columns, applicable across a wide range of parameters, was proposed.