Axial compression behavior of corner-stiffened concrete-filled double-skin steel tubular (CFDST) members: Experimental and analytical research

Traditional square concrete-filled double-skin steel tubular (CFDST) member inevitably has the limitation of stress concentration at the steel tube corners, making it difficult to meet the development needs of heavy-load structures. This paper proposed a new-type corner-stiffened CFDST members for the potential application in the towers or piers of long-span bridges. An axial compression test was conduct to investigate its compressive behavior, where the failure mode involved the inward buckling of inner steel tube, outward buckling of flat steel plate and corner steel tube, and the concrete crushing. A finite element (FE) model was verified in terms of the failure mode, full-range load-displacement curve and maximum bearing capacity, for the further mechanism analysis and parametric study. Mechanism investigation reflects that: the reinforcement of corner concrete-filled steel tubular (CFST) members intensifies the confining stress between the corner concrete and corner steel tube within the reinforced zone; the flat steel plate and inner steel tube function independently, without generating substantial confining stress. Parametric study on material-geometric parameters reveals that: inner steel tube strength ( f yi ) has a slight effect on the compressive capacity, e.g., the bearing capacity respectively improves by 1.85 % and 2.98 % as f yi increases from 355 MPa to 460 MPa and 550 MPa; inner steel tube strength, diameter-to-thickness ratio of inner steel tube, and hollow ratio slightly affect the confining stress of the corner CFST component. Finally, the calculation method was established and validated for predicting the compressive capacity of corner-stiffened CFDST members.