GBT-based assessment of the buckling behaviour of cold-formed steel purlins restrained by sheeting

• Buckling analysis of lipped channel and zed cold-formed steel purlins restrained by steel sheeting.
• GBT-based assessment of the local/distortional/global buckling of purlins under uplift loading.
• Sheeting restraint modelled through elastic translation/rotation springs at purlin upper flange.
• Purlins with strengthened/lapped joints at internal/intermediate supports are also investigated.
• A GBT-based strategy to determine “optimal joint strengthening/lap lengths” is proposed.

This paper presents and discusses the results of a GBT-based numerical investigation concerning the local, distortional and global buckling behaviour of lipped channel and zed-section cold-formed steel purlins restrained by steel sheeting and subjected to an uplift loading. Strengthened (lapped) joints, commonly employed at internal supports to preclude the occurrence of local/distortional buckling phenomena, are also investigated and an illustrative application of the use of GBT to determine strengthening lengths is also presented. The sheeting restraint is modelled by means of elastic translational and rotational springs, located at the purlin upper flange, and the joint strengthening is modelled by doubling the cross-section wall thickness. For validation, the GBT-based results are compared with values yielded by Ansys shell finite element analyses.