Buckling behavior of UHPC filled stainless steel tubular columns subjected to eccentric compression

Ultra-high Performance Concrete (UHPC) filled stainless steel tubular (UHPCFSST) column is a new type of concrete filled steel tubular (CFST) composite columns prospective to be adopted in offshore construction. As a follow-up work of previous study focusing on concentric behavior and interfacial properties, this paper delves into the eccentric compressive behaviour of UHPCFSST columns through experimental investigation and analytical derivation. A total of 10 UHPCFSST column specimens varying in slenderness ratio, tube diameter-to-thickness ratio and load eccentricity ratio were tested to explore the load-deformation response, damage pattern, stiffness, ductility and load-carrying capacity under eccentric compressive loading. Moreover, in-depth analysis was conducted to provide deep insight into the composite action between stainless steel tube and UHPC. To promote the application of UHPCFSST columns in practice, current international design codes of conventional CFST columns were comparatively reviewed for the prediction of axial force-bending moment (N-M) interaction diagram. In view of the limitation of current methods, an improved approach with consideration of confinement effect and UHPC tensile strength was proposed to assist the design of UHPCFSST columns.