Abstract
Cold-formed stainless steel is becoming popular as a structural member with its increased corrosion resistance and durability when compared with carbon steel. Examples of cold-formed steel structures include trusses, wall frames and portal frames. In cases where increased axial strength is required, it is becoming increasingly popular to use battened built-up channel sections, instead of just back-to-back channel sections. For carbon steel battened built-up columns, limited experimental and finite element (FE) results are available in the literature. These results, however, are not applicable to cold-formed stainless steel. This issue is addressed numerically herein. Using the finite element model (FEM) previously reported by the first author of this paper for cold-formed carbon steel, an extensive parametric study, comprising 132 models is described in this paper for stainless steel battened builtup columns. Two different grades of stainless steel, that is, austenitic EN1.4404 and ferritic EN1.4003 have been considered. The effects of slenderness, different cross-sectional geometries and batten depth are investigated. From the results of parametric study, it was found that most of the short, intermediate, and long columns failed by distortional-flexural buckling interaction. For stub columns, distortional buckling governed the failure mode. The axial strengths determined from the parametric study were then compared against the design strengths calculated by the design guidance of carbon steel built-up columns from the American Iron and Steel Institute (AISI (2016)) and Australian and New Zealand Standards (AS/NZS (2018)). This is due to the unavailability of design guidelines for stainless steel battened built-up columns. From the comparison, it was found that the design strengths are 4% conservative on average for stainless steel battened built-up columns. Therefore, a design recommendation is proposed to modify the current design rules of carbon steel built-up columns, which was found to be accurate for stainless steel battened built-up columns.