Effect of screw spacing into the behaviour of back-to-back cold-formed duplex stainless steel built-up channel sections under compression

Abstract

Stainless steel is becoming popular as structural members because of its increased corrosion resistance and durability. In CFS structures, built-up cold-formed stainless steel channels, connected back-to-back, are becoming increasingly popular as compression members. Current guidance by the American Iron and Steel Institute (AISI) and the Australian and New Zealand Standards for built-up carbon steel sections describes a modified slenderness approach, to take into account the spacing of the fasteners. Although, the AISI & AS/NZS does not include stainless steel built up columns. Limited experimental tests or finite element analyses have been reported in the literature for such back-to back cold-formed stainless steel lipped channel sections. The issue is addressed in this study. This paper presents a numerical investigation into the behaviour of back-to-back cold-formed duplex stainless steel built-up columns. A comprehensive parametric study has been carried out covering a wide range of slenderness and different cross section geometries to assess the performance of the design guidelines by AISI & AS/NZS. In total, 78 FE models were analysed. The effect of screw spacing on axial capacity was investigated. From the results of the parametric study, it was found that the current design guidelines are conservative by around 15% for all columns failed through overall buckling, however, design standards were un-conservative by around 6% for columns failed through local buckling.