Compression tests of cold-formed steel I-shaped open sections with edge and web stiffeners

A series of column tests on cold-formed steel I-shaped open sections with edge and web stiffeners has been conducted. The test specimens were firstly brake-pressed from high strength zinc-coated steel sheets and then two of the same members were connected back-to-back by self-tapping screws to form an I-shaped section with edge and web stiffeners. The members had the nominal thicknesses of 0.48, 1.0 and 1.2 mm. The column length of the test specimens varied from 300 to 3200 mm with an increment of approximately 600 mm. The column specimens were compressed between fixed ends. Tensile coupon tests were also conducted to obtain the material properties at both flat and corner portions of the sections. Initial local and overall geometric imperfections were measured. The columns were failed by local, distortional, flexural buckling and the interaction of these buckling modes. The failure modes and ultimate strengths of the column specimens were presented. The direct strength method in the North American Specification and the Australian/New Zealand Standard was used to calculate the design strengths of the I-shaped open section columns. The appropriateness of the direct strength method for I-shaped open sections with edge and web stiffeners was evaluated. In addition, the reliability of the direct strength method for the I-shaped open sections was evaluated using reliability analysis. It is shown that the direct strength method can be used for cold-formed steel I-shaped open sections with edge and web stiffeners.