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This paper describes a series of compression tests performed on long columns fabricated from cold-formed high strength steel plates with nominal yield stress of 550 MPa. The steel is classified as G550 to Australia Standard AS1397. The test results presented in this paper are the second stage of an Australian Research Council research project entitled “Compression stability of high strength steel sections with low strain-hardening.” A total of 28 long columns, which were made from two thicknesses of sheet steel (0.42 and 0.6 mm), were tested. A box shaped section was tested between pinned ends over a range of lengths. This paper shows the comparison of loads obtained experimentally with those predicted on the basis of AS/NZS 4600 and the AISI specification including Supplement No. 1, 1999. The finite element program, ABAQUS, was also used to simulate the column behavior. For sections which undergo local instability at loads significantly less than the ultimate loads, the column design rules in AS/NZS 4600 and the AISI Specification are unconservative if used in their current form for G550 steel. Proposals for improved column design of high strength slender sections are proposed in this paper. A first companion paper (Part I) describes a series of compassion tests on stub columns. [ABSTRACT FROM AUTHOR]

In roof systems, a high strength steel profiled sheeting fastened to high strength steel cold-formed purlins of a lipped C- or Z-section is commonly used throughout the world. The design of such systems is performed according to the provisions of the limit states Australia/New Zealand Standard for Cold-Formed Steel Structures in Australia and the North American Specification for the Design of Cold-Formed Steel Structural Members in the United States. In both standards, which include the newly developed direct strength method of design (DSM), the method presented 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 the lipped channel section were tested in this study. Further, tests with and without torsion/distortion restraint straps screwed on the top flanges adjacent to the loading points were also considered. This paper summarizes the test results and formulas developed from the effective width method and the DSM. Proposals for design are included in this paper. Comparisons with the Australian Steel Structures Standard are also included to take account of the tension field action. [ABSTRACT FROM AUTHOR]

This paper describes a series of compression tests performed on stub columns fabricated from cold-formed high strength steel plates with nominal yield stress of 550 MPa. The steel is classified as G550 to Australia Standard AS1397. The test results presented in this paper are the first stage of an Australian Research Council research project entitled “Compression stability of high strength steel sections with low strain-hardening.” The tests include lipped-square and hexagonal sections, including 94 box-shaped fix-ended stub columns. The purpose of these tests was to determine the influence of low strain hardening of G550 steel on the compressive section capacities of the column members. The results of the successful stub column tests have been compared with the design procedures in the Australian/New Zealand Standard for Cold-Formed Steel Structures and recent (1999) amendments to the American Iron and Steel Institute Specification. As expected, the greatest effect of low strain hardening was for the stockier sections where material properties play an important role. For the more slender sections where elastic local buckling and postlocal buckling are more important, the effect of low strain hardening does not appear to be as significant. This is contrary to recent design proposals in the USA where it was proposed that the more slender sections would be more greatly influenced by low strain hardening. A simple proposal for improved design capacity is given in the paper. A second companion paper (Part II) describes a series of compression tests on long columns made from the same material. [ABSTRACT FROM AUTHOR]