Compression Tests of Cold-Reduced High Strength Steel Sections. II: Long Columns

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 $550\mathrm{MPa}$. 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 $0.6\mathrm{mm}$), 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.