Axial compressive behavior of FRP-concrete-steel double skin tubular columns with a rib-stiffened Q690 steel tube and ultra-high strength concrete

•Compressive behavior of DSTCs with high-strength steel tube and ultra-high strength concrete is studied and presented.•The axial load-axial strain curves exhibit an ascending-descending-ascending-failure behavior.•The stiffeners are beneficial in enhancing the performance of DSTCs.•The existing model is inaccurate in predicting the ultimate axial stress and the ultimate axial strain of high/ultra-high strength concrete in DSTCs. Fiber-reinforced polymer (FRP)-concrete-steel double skin tubular columns (DSTCs), which possess an outer FRP tube, an inner steel tube and sandwiched concrete between both tubes, are a kind of hybrid column with a particular merit of lightweight. It is expected that using high-strength materials (i.e., ultra-high strength concrete (UHSC) and high-strength steel (HSS) tubes) in DSTCs magnifies the merit of DSTCs. This paper presents an experimental study on axial compression behavior of DSTCs with ultra-high strength concrete and a rib-stiffened Q690 steel tube. The rib-stiffened steel tubes, which are less susceptible to local buckling compared with those without stiffeners, were used in the present study. The parameters including the quantity of stiffeners, the length of stiffeners, the FRP tube thickness, the steel tube diameter and the concrete strength were carefully designed and investigated through the experimental study. The test results demonstrate that DSTCs with UHSC and HSS tubes exhibit a ductile behavior and the axial load-axial strain curves exhibit an ascending-descending-ascending-failure behavior. Additionally, the stiffeners are beneficial in enhancing the performance of DSTCs. The comparisons between the test results and theoretical results show that the existing model of Yu et al. is inaccurate in predicting the ultimate axial stress and the ultimate axial strain of HSC and UHSC in DSTCs.