Compressive behaviour and design of square concrete-filled stainless steel double-skin tubular short columns

This study thoroughly examines the strength, ductility, and ultimate resistance of square concrete-filled double-skin stainless steel tubular (CFDST) short columns with outer stainless steel tubes, based on the relatively limited available data on the literature. Three stainless steel grades were examined, namely the austenitic stainless steel grades EN 1.4301 and EN 1.4318 and the duplex stainless steel grade EN 1.4462. A numerical model was developed and validated using experimental data. The parameters considered in this study include the slenderness ratios of the outer and inner tubes, concrete compressive strength, yield stress of the outer tube, and section hollow ratio. These extensive parametric studies identify concrete strength and outer tube slenderness as key influencing factors to the overall behaviour and capacity. Then, the applicability of design rules from European and North American specifications, along with methods proposed in the literature was evaluated against numerical results. The findings indicate that almost of these methods yield unconservative resistance predictions, with just the method proposed by the AISC 360 providing safe estimates for the ultimate resistance. However, none of the five design methods examined ensured the structural integrity of the columns, as measured by the reliability index. Finally, a modification to the Eurocode 4 design equation has been made to get safe, accurate, and reliable strength predictions. • Behaviour of SS-CFDST under axial compressive loading is investigated. • FE models of the columns were developed and validated against available test data. • Failure modes observed were local buckling. • A method for calculating the ultimate axial capacity of the columns is proposed.