Theoretical analysis of partially restrained zed-purlin beams subjected to up-lift loads

Cold-formed steel section beams are usually used as the secondary structural members in buildings to support roof and side cladding or sheeting. Thus these members are commonly treated as the restrained beams either fully or partially in its lateral and rotational directions. In this paper an analytical model is presented to describe the bending and twisting behaviour of partially restrained cold-formed steel purlins when subjected to uplift loading. Formulae used to calculate the bending stresses of the roof purlins are derived by using the classical bending theory of thin-walled beams. Detailed comparisons are made between the present model and the simplified model proposed in Eurocodes (EN1993-1-3). To validate the accuracy of the present model, finite element analysis is also conducted and the bending stress distribution along the lip, flange and web lines obtained from the finite element analysis is compared with those obtained from the present and EN1993-1-3 models.

► It presents an analytical model describing bending and twisting behaviour of purlins
► It derives the formulae to calculate the bending stresses of roof purlins.
► It provides detailed comparisons between different models and calculation methods.
► It provides an illustration of the development of the EN1993-1-3 model.