Cold-formed steel channel sections with web stiffeners subjected to local and distortional buckling - Part I: Tests and finite element analysis

An experimental investigation of simply supported beams with two different stiffened channel sections has been conducted under both four-point bending and three-point bending about the major axis of the sections. Stiffeners were employed to the web of plain channel and lipped channel sections to improve the flexural strength of cold-formed steel sections that are prone to local buckling and distortional buckling. In this study, the channel sections were brake-pressed from high strength zinc-coated grades G500 and G550 structural steel sheets with nominal 0.2% proof stresses of 500 and 550 MPa, respectively. The high strength stiffened channel sections had the thicknesses of 0.48, 1.0 and 1.2 mm. Material properties were obtained from the tensile coupon tests. The moment capacities and observed failure modes at ultimate loads in the beam tests were reported. A nonlinear finite element model (FEM) was developed and verified against the test results in terms of strengths, failure modes and moment- curvature curves. It is shown that the FEM well predicted the moment capacities and failure modes of the test beams.