WEB ROTATIONAL RESTRAINT IN ELASTIC DISTORTIONAL BUCKLING OF COLD-FORMED LIPPED CHANNEL SECTIONS

The distortional buckling is one of important buckling modes for cold-formed lipped channel sections and the distortional buckling load depends significantly on the rotational restraint provided by the web to the flange during buckling deformation. So the thorough study on the rotational restraint for elastic distortional buckling analysis is presented. Analytical expressions for the rotational restraint are first derived for eight cases representing different combinations of stress states and deformation shapes of the web. Based on these analytical expressions, the effect of the deformation shape of the web is discussed in detail. Finally, an accurate simplified expression for the rotational restraint is proposed. The results of the present study are expected to be useful for the future development of a simple approximate formula for the distortional buckling load of cold-formed lipped channel columns for design use.