ABSTRACT
In this study, an experimental program was conducted to investigate the buckling behaviour of cold-formed steel built-up open section members under combined axial load and bending. A total of 15 eccentrically loaded compression tests with varying initial moment-to-axial load ratio were carried out. The built-up open sections were consisted of two identical channels with both intermediate and edge stiffeners connected back-to-back using self-tapping screws. The channel sections were brake-pressed from zinc-coated grade G550 and G500 steel sheets with nominal thicknesses of 0.75 and 1.2 mm, respectively. The test specimens with nominal lengths of 300 and 900 mm were loaded under pin-ended boundary conditions. The test setup, experimental procedure, observed failure modes and test results are reported. The predicted strengths determined from the provisions specified in the North American Specification were compared with the strengths obtained from the tests. The predicted strengths are conservative for the built-up open section beam-columns.
