Numerical investigation on the composite action of cold-formed steel built-up battened columns

Cold-formed steel (CFS) built-up sections are widely used to achieve adequate load-bearing capacity when individual shapes are not able to resist the design loads. In the existing codes, there are few guidelines for designing and fabricating these members. This paper evaluates the influence of fastener patterns and spacing as well as reinforcing plates on the global and local buckling behavior of the CFS battened columns comprising two individual lipped channels. A large set of experimental results, available in the literature, were considered for the calibration of the developed numerical models. The effectiveness of the composite action between all profiles is crucial to fully exploit the capabilities of the built-up sections. To evaluate the performance of the investigated battened columns as well as the influence of spacing and configuration of the connecting plates, a large numerical investigation was undertaken. The results showed improved axial load-bearing capacity for the CFS battened columns when the number of fasteners rows was increased. Considering the spacing of the battened plates and their configuration, detailed analysis was conducted on the predominant buckling modes. The numerical results were also compared with analytical predictions based on Eurocode and the North American Specification (NAS). The results of this paper recommend that three rows of fasteners per battened plate are the optimal scenario for achieving composite action within the CFS built-up sections.