Closed built‐up cold‐formed steel columns under compression

Cold‐formed steel (CFS) structural profiles are extremely versatile enabling the combination of multiple individual cross‐section shapes to fabricate a built‐up member presenting enhanced structural performance (higher load‐bearing capacity and torsional stiffness). Built‐up members have the potential to contribute to further expanding the current use of CFS products in the construction industry. However, the existing design codes, such as the EN 1993‐1‐3 and AISI S100, do not present specific design methodologies for the design of such members, mainly due to a limited understanding of the complex behaviour of built‐up CFS members combining multiple components. The behaviour of built‐up CFS columns comprising 4 individual shapes was assessed through experimental tests and numerical modelling. The interaction between the different components and the influence of spacing between connectors was investigated using the finite element method, providing recommendations concerning the effective use of fasteners to attain composite action between the individual shapes. The suitability of the design codes, namely, Eurocode and North American design predictions, following to Effective Width Method (EWM) and Direct Strength Method (DSM), respectively, were assessed for the built‐up members.