Carrying Capacity of Back‐to‐Back Cold‐Formed Thin‐Walled U Profiles Subjected to Compression

Thin‐walled cold‐formed members are mainly used in rack structures due to their light weight and the variety of cross‐sections of different shapes that can optimize the design process. However, in cases where bigger span distances or higher resistances are required, the use of single members is not adequate and built‐up sections deem to be necessary. To form such sections, single sections are connected with intermediate fasteners, with or without packing plates. Although the effect of these intermediate connections is considered in some international standards such as the American and the Australian ones, the latter is totally neglected in EN 1993‐1‐3. Rules are only found in EN 1993‐1‐1 related to closely‐spaced battened members, but their possible extension to cold‐formed thin‐walled sections could be questionable and needs further validations. This paper presents numerical and analytical studies aiming at investigating the validity and applicability of these design rules for predicting the buckling resistance under pure compression of a battened built‐up member consisting of two back‐to‐back thin‐walled U profiles. In this framework, a specific attention is paid to the effects of the shear stiffness associated to the batten plates. Finally, design recommendations are provided.