Stub Column Response in Light of Local vs Distortional Buckling

The objective of this paper is to study the effect of distortional buckling on the stub column testing that is typically used by industry to determine effective area of the members under compression. The testing standards (e.g. AISI S902) are intended to experimentally determine the effective area of the stub columns, however, other failure modes like distortional buckling or local premature failures at the ends of the specimens can potentially occur prior to the local buckling and therefore, the effective area would be underestimated. This could end up in underestimating the capacity of the longer compressive members in design of the real structure, where the overall capacity of the cross-section could be knocked down even more due to local-global buckling interaction. An experimental study on lipped channels and rack sections with relatively lower distortional buckling than the local buckling capacity has been conducted at Thin-Walled Structures Laboratory in Johns Hopkins University to shed light on the effect of other failure modes on the calculation of the effective area. Different end conditions including, bare, in-track, welded, clamped, and also different means of artificially postponing the distortional buckling are examined experimentally and practical recommendations have been provided on how to conduct experiments to get more realistic effect area in stub columns testing.

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