Structural Behaviour of Cold-Formed Steel Built-Up Beams

Cold-Formed Steel (CFS) built-up beams are used widely in the construction industry. In the current study, an experimental investigation of simply supported built-up beams with intermediate web stiffeners was carried out under both three-point and four-point bending. The built-up sections were assembled from press-braked sigma-shaped open sections connected back-to-back and front-to-front by spot welding at flanges to form I-sections and hollow tubular sections respectively. A total of 30 specimens comprising of both I and hollow sections for various beam lengths and intermediate connection spacing were tested. The observed failure modes and the obtained moment capacities from experiments are presented along with a comparison of moment capacities predicted using the North American Specification’s Direct Strength Method (DSM). The findings indicate that the AISI’s DSM method of moment calculations was found to be conservative for few specimens and unconservative for the majority of the test specimens.