Buckling of fixed-ended concrete-filled steel columns under axial compression

In recent years, due to a relatively high price increase of nickel alloys, there is an increase in demand for lean duplex stainless steel (LDSS) with a low nickel content of ~1.5%, such as grade EN 1.4162. LDSS offers roughly twice the strength compared to austenitic stainless steels and has great potential for expanding future structural possibilities, enabling a reduction in the section sizes leading to lighter structures. This paper reports the buckling behavior of fixed-ended concrete-filled LDSS tubular (CFDSST) columns with L-, T-, and +-shape (Non-Rectangular Sections or NRSs) sections and a representative square section with varying lengths through Finite Element (FE) analysis. The purpose is to compare and assess the strength and deformation characteristics as well as the failure modes of such columns. It is seen that concrete-filled tubular columns with NRSs offered a better performance for all lengths considered, especially the T-shaped and +-shaped sections, in terms of strength. The influence of the cross-sectional shapes on the εu becomes less significant with increasing λ, but becomes increasingly significant with decreasing λ. The design standards show over conservative results for square and L-shape sections and conservative for T-shape and +-shape sections.