DESIGN OF LIPPED CHANNEL COLUMNS

The paper describes a series of tests on lipped channels compressed be tween fixed ends. Complete column curves were obtained for two cross s ections with different flange slenderness. Detailed measurements were conducted of the material properties, residual stresses, and local and overall geometric imperfections. The test strengths are compared with the rules of the Australian, American, and European specifications fo r cold-formed steel structures. It is shown that a fixed-ended channel column can be designed using an effective length of one-half of the c olumn length and assuming the applied force acts at the centroid of th e effective section. Pin-ended column tests of the same cross sections were conducted for reference. It was shown that the current design ru les lead to very conservative predictions. The shift of the effective centroid, as predicted by the Australian and American specifications, was shown to be inaccurate compared with the tests for the cross secti on with slender flanges. This led to the abnormal result of an increas e in column strength with increasing length.