Lateral–torsional buckling of cold-formed zed-purlins partial-laterally restrained by metal sheeting

This paper presents an analytical model for predicting the lateral–torsional buckling of cold-formed zed-purlins partial-laterally restrained by metal sheeting for both down and uplift loadings. The critical load is determined by using energy methods. The focus of the study is to investigate the individual influences of restraints provided by the sheeting and by interval anti-sag bars, the variation of moment distribution along the longitudinal axis, and boundary conditions on the lateral–torsional buckling behaviour of the purlin.