Compressive Capacity of Cold-Formed Steel High Strength Low-Alloy Lipped Channels with Intermediate Stiffeners

We report herein a set of compression tests on high strength low alloy (HSLA) cold-formed steel steel sections intended for use as piles. The specimens are lipped channels with outer cross-section dimensions of 6 in. wide and 4 in. deep, and include 1 in. lips and feature two intermediate flat hat-shaped stiffeners in the web, one intermediate stiffener in the flange, and return lips. The HSLA employed has a measured mean yield stress of 100.5 ksi and a nominal thickness of 0.075 in. The compression tests were conducted between rigid steel end platens and resulted in highly repeatable strengths at all studied lengths: 12 in., 24 in. and 48 in. Mean peak strength for the shortest 12 in. long specimens was 85.3 kips, followed by 80.1 kips for the 24 in. long specimens, and 74.1 kips for the 48 in. long specimens. Tested strengths were compared to predictions using the Direct Strength Method of AISI S100 and assuming either simply supported or clamped end boundary conditions. Although the test conditions only use end bearing, best agreement is still found when assuming clamped end boundary conditions, mean test-to-predicted ratio is 1.16 assuming simple ends and 0.97 assuming clamped ends. In addition, work to summarize measured geometric imperfections, comparisons against a set of companion tests using advanced high strength sheet steels, and potential future work items are all discussed.
cold-formed steel, solar array pile, HSLA, Direct Strength Method