Experimental investigation of high strength cold-formed SupaCee® sections in combined bending and shear

High strength steel cold-formed purlins of lipped C or Z-sections are commonly used throughout the world, one of which is the SupaCee® section (Lysaght, 2003). They contain additional return lips and web stiffeners which enhance the bending and shear capacity of the sections. These sections are widely used in Australia as purlins in roof and wall systems. Design methods for these sections are normally specified in the Australian/New Zealand Standard for Cold-Formed Steel Structures AS/NZS 4600:2005 (Standards Australia 2005) or the North American Specification for Cold-Formed Steel Structural Members (AISI 2007). In both Standards, which include the newly developed Direct Strength Method of design (DSM), the method presented [Chapter 7 of AS/NZS 4600:2005 (Standards Australia 2006), Appendix 1 of (AISI 2007)] is developed for beams and columns, including the reliability of the method. Both the Effective Width Method (EWM) and the Direct Strength Method (DSM) can be used for the design of C-sections although no formal rules for shear and combined bending and shear exist for the DSM in either standard/specification. This report presents three different test series on SupaCee® sections performed at the University of Sydney for the extension to the DSM for shear, and combined bending and shear. The test series include predominantly shear, combined bending and shear, and bending only test series. Two different section depths and three different thicknesses of lipped channel section were tested and are described in this report. Tests with and without torsion/distortion restraint straps screwed on the top flanges adjacent to the loading points were also considered. The test data were used to compare with the existing EWM without tension field action. The report also proposes new DSM formulae based on the North American Specification in DSM Format in shear without tension field action and a proposal in DSM Format including tension field action. Both test results and formulae developed from the EWM and DSM are summarized. © 2009 Cao Hung Pham and Gregory J. Hancock.