Buckling curves of stainless steel CHS members: Current state and proposed provisions

Abstract

The study objective is to propose the optimal shape of the flexural buckling curves for stainless steel circular hollow cross-section (CHS) members. It has been pointed out by several researchers, that the currently utilized buckling curves do not fulfil the required structural reliability level, and several provisions have already been proposed. Following this research, our proposals are based on a numerical investigation of the ultimate limit state of geometrically imperfect stainless steel CHS columns of three different material grades (Austenitic 1.4307, Ferritic 1.4003 and Duplex 1.4462) using the statistical characteristics of input initial imperfections, material and geometric parameters. The statistical characteristics are considered according to the results of published research. The first-order reliability method (FORM) supported by the advanced finite element method – geometrically and materially nonlinear imperfect analysis (GMNIA) – is used. The values of the ultimate resistance obtained using FORM are compared with the values of the design resistance determined according to the corresponding European standards and are used to determine the optimal shape of flexural buckling curves. Additionally, the influence of linear correlation between the ultimate resistance of CHS stainless steel columns exposed to flexural buckling and input imperfections is discussed. Studies have shown that the maximum effect of initial axial curvature on resistance occurs at higher slenderness compared to carbon steels. The obtained results present provisions to optimize the flexural buckling curves of stainless steel CHS members and could significantly improve the structural efficiency, resulting in material savings, while preserving the required level of structural reliability.