Experimental Investigation of High Strength Cold-Formed C-Section in Combined Bending and Shear (No. R894)

Abstract

In roof systems, high strength steel profiled sheeting fastened to high strength steel cold-formed purlins of lipped C or Z-section are commonly used throughout the world. The design of such systems is performed according to the provisions of the limit states Australia/New Zealand Standard AS/NZS 4600:2005 (Standards Australia 2006) in Australia and the North American Specification (NAS) for the Design of Cold-Formed Steel Structural Members (AISI 2007) in the USA. In both Standards, which include the newly developed Direct Strength Method of design (DSM), the method presented [Chapter 7 of AS/NZS 4600:2005, Appendix 1 of (AISI 2007)] is limited to pure compression and pure bending. The situations of pure shear and combined bending and shear as occurs in a continuous purlin system are not considered. In order to extend the DSM to purlin systems, three different test series on high strength cold-formed C-section purlins have been performed at the University of Sydney. 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 in this study. Farther, tests with and without torsion/distortion restraint straps screwed on the top flanges adjacent to the loading points were also considered. This report summarizes the test results and formulae developed from the Effective Width Method (EWM) and Direct Strength Method of Design (DSM). Proposals for design are included in this report. Comparisons with AS 4100:1998 (Standards Australia 1998) are also included to take account of tension field action.