Performance and design of concrete-filled sleeve-connected stainless steel tubular stub column under axial compression

To meet the critical construction challenges in mountainous and offshore areas, a novel concrete-filled sleeve-connected stainless steel tubular column (sleeve-connected CFSST) is developed by manufacturing the stainless steel tubes in controlled length for convenient transport and assembling on-site with sleeve connection. The spliced steel tubes can further act as formwork to fill on-site mixing concrete for efficient composite action. In this study, the failure modes, load-carrying capacity and ductility of sleeve-connected CFSST columns under axial compressive loading are experimentally investigated with different spliced types. The test results indicates that the outer sleeve can provide additional confinement, leading to strength and ductility enhancement in sleeve-connected CFSSTs. Then finite element (FE) model is validated by the test data, the load-transfer mechanism and confinement effect in typical spliced CFSST columns are systematically analysed by the verified FE model, demonstrating that the existence of core concrete has positive effect on spliced steel tube in transferring axial load and providing additional confinement. Furthermore, the existing design codes give conservative predictions in load-carrying capacity of sleeve-connected CFSSTs. Based on parameter analysis, current predicted methods in cooperation with suggested influenced factor is proposed for compression capacity prediction. Meanwhile, several design recommendations are also delivered within a limited scope.