Resistance of cold-formed sorbite stainless steel circular tubes under uniaxial compression

Recently developed novel high-strength sorbite stainless steel (S600E) integrates the merits of exceptional mechanical properties, high corrosion resistance, effortless weldability, and cost-effectiveness, offering remarkable competitiveness in stainless steel structures. However, the lack of information regarding its mechanical performance impedes its application as a structural component in the construction industry. In this paper, material tensile tests, axial compression stub column tests, and axial compression long column tests were conducted to determine the constitutive curves, failure patterns, and ultimate capacity of cold-formed S600E high-strength stainless steel with a circular hollow section (CHS). The experimental results demonstrate that the material strength of S600E increases to a yield and ultimate strength of 580 MPa and 690 MPa, respectively. In addition, all stub columns are in a local buckling mode, with an “elephant foot” shape at one end, whereas all long columns fail by the overall buckling. To find an accurate ultimate capacity prediction method for the studied columns, the experimental data were compared with those of existing standards and methods. The comparisons demonstrate that (1) for stub columns, all the existing approaches evaluate the axial resistance conservatively, where the continuous strength method (CSM) delivers comparatively precise predictions; and (2) for long columns, the design strength recommended by Australian/New Zealand codes proves to be unsafe. Conversely, the direct strength method (DSM) holds an overly cautious attitude. Among the codes, the Chinese code accurately assesses axial resistance. The findings of this study inform mechanical behaviors for designers and engineers to facilitate the use of high-strength sorbite stainless steel.