Tests of fixed-ended plain channel columns

The paper describes a test program on cold-formed plain channel columns compressed between fixed ends and pinned ends. Whereas it is well-known that local buckling of pin-ended channel columns induces overall bending, this phenomenon does not occur in fixed-ended channel columns that remain straight after local buckling and only bend when overall buckling occurs. These fundamentally different effects of local buckling on the behavior of pin-ended and fixed-ended channel sections lead to inconsistencies in traditional design approaches, which account for full or partial rotational end restraint solely by using effective lengths. A series of tests was performed for different geometries of cross section fabricated by brake pressing from high-strength steel sheet. Tests were performed over a range of lengths such that the column curve could be obtained. Local buckling loads were also obtained from the fixed-ended column tests. Detailed measurements of local and overall geometric imperfections, material properties, and residual stresses were conducted. The purpose of this paper is first to present and compare the test strengths with existing Australian/New Zealand, American, and European specifications for cold-formed steel structures and, second, to propose recommendations for the design of fixed-ended singly symmetric columns.