Compression Tests of Cold-formed Steel Built-up Closed Sections with Web Stiffeners

Abstract

This paper describes an experimental investigation of cold-formed steel built-up closed sections compressed between fixed ends. Two built-up closed section types, one with inward web stiffeners, and the other with outward web stiffeners, were tested. The test specimens were firstly brake-pressed from high strength zinc-coated steel sheets. Then, two of the same sections were connected face-to-face by self-tapping screws to form a built-up closed section. The members had the nominal thicknesses of 0.48 and 1.0 mm. The column length of the test specimens varied from 300 to 3200 mm, with an increment of approximately 600 mm. The material properties were obtained by tensile coupon tests. The failure modes including local buckling and interaction of local and flexural buckling were observed in the tests. The appropriateness of the direct strength method in the North American Specification and Australian/New Zealand Standard for cold-formed steel structures was evaluated based on the test results. It is shown that the direct strength method can be used for cold-formed steel built-up closed sections with web stiffeners.