Numerical investigation into the buckling behaviour of face-to-face built-up cold-formed stainless steel channel sections under axial compression

Abstract

Stainless steel is becoming popular as structural members because of its increased corrosion resistance and durability, compared with carbon steel. In cold-formed steel structures, such as trusses, wall frames and portal frames, the use of face-to-face built-up cold-formed stainless steel channel sections as compression members are becoming increasingly popular. In such an arrangement, intermediate fasteners at discrete points along the length prevent the individual channel sections from buckling independently. Current guidance by the American Iron and Steel Institute (AISI) and the Australian and New Zealand (AS/NZS) standards for built-up sections describes a modified slenderness approach, to take into account the spacing of the screws. Not even a single experimental test or finite element analysis, however, have been reported in the literature for such face-to-face built-up stainless steel channel sections, to understand the effect of screw spacing. The issue is addressed numerically herein. This paper presents a finite element investigation on the behaviour of face-to-face cold-formed stainless steel built-up channel sections, subjected to axial compression. Three different grades of stainless steel i.e. duplex EN1.4462, ferritic EN1.4003 and austenitic EN1.4404 have been considered. The effect of screw spacing on axial strength of face-to-face built-up stainless steel channel sections was investigated. A comprehensive parametric study was carried out, covering a wide range of slenderness and different cross sectional geometries to assess the performance of the current design guidelines by AISI and AS/NZS. In total, 160 finite element models were analyzed. From the results of the parametric study, it was found that the AISI & AS/NZS are conservative by around 15% for all stainless steel face-to-face built-up columns failed through global buckling. However, the AISI & AS/NZS are un-conservative by around 5% for face-to-face built-up stainless steel columns failed through local buckling.