Simple formulae for distortional buckling loads of cold-formed lipped channel sections for integrating processes

The determination of the elastic distortional buckling loads of the cold-formed lipped channel sections subjected to the eccentric compression and the pure bending was performed based on the analytic solutions combined with the finite strip buckling analyses. The parameter analyses were carried out an the distortional buckling under two extreme load cases of axial compression and pure bending, leading to an approximate formulae for predicting the buckling half-wavelength and the modified factor to take into account the effect of the shear and distortional deformation of the flange section. The rotational restraint, provided by the web to the flange during buckling deformation, was then examined, and a more accurate linear approximate expression for the rotational restraint and the web stress was proposed. Based on these approximate formulae/expressions, the two simplified formulae were finally developed to predict the elastic distortional buckling loads of the cold-formed lipped channel sections subjected to the eccentric compression and the pure bending. These two proposed formulae are shown to be accurate through comparisons with the results of finite strip buckling analyses, easy to be applied, may be used in practical applications and taken account into design codes and guidelines. A simple example was also included in the study.