Column tests of cold-formed steel channels with complex stiffeners

This paper presents an experimental investigation of cold-formed steel channels with complex stiffeners subjected to pure axial compression for fixed-ended columns. The complex stiffeners of the channel sections consist of simple lips with return lips. A total of 30 column specimens were tested. The specimens were brake pressed from high strength zinc-coated structural steel sheets. Four different cross sections with different flange slenderness were tested over a range of column lengths. Detailed measurements of material properties, geometric imperfections, and local buckling loads of the specimens were conducted. Interaction of local and overall buckling was observed in the tests. Failure modes include local buckling, distortional buckling, and flexural-torsional buckling. The test strengths of the columns are compared with the design strengths predicted by the American Specification and the Australian/New Zealand Standard for cold-formed steel structures. Design column curves are also plotted. It is shown that the design strengths predicted by the American Specification are generally unconservative for short and intermediate columns, whereas the design strengths predicted by the Australian/New Zealand Standard are generally conservative for all column lengths. This is because the Australian/New Zealand Standard has a separate check for distortional buckling of singly symmetric sections.