Lateral Buckling Tests on Cold-Formed Z-Beams
Publication: Journal of Structural Engineering
Volume 125, Issue 11
Abstract
This paper is concerned with the lateral buckling capacities of cold-formed lipped Z-beams (CFZs). It is argued that design code formulations that are based on those for hot-rolled I-beams may be inappropriate for CFZs, because of the very different cross-sectional shapes and methods of manufacture, and that there is a need for test data on the lateral buckling capacities of CFZs. Described are a series of six lateral buckling tests on simply supported, unbraced CFZs, and a series of subsidiary tests, including tension tests, a torsion test, and measurements of initial crookedness and twist. The test beams failed catastrophically by local or distortional buckling of the most compressed element of the cross section. The moments at failure were lower when the beam lateral deflections increased the compression in the compression flange lip, and higher when they increased the compression in the flange-web junction. The lateral buckling test results are compared with theoretical predictions and with capacities calculated using existing design codes AS4100 and AS/NZS4600. Agreement between the test results and theoretical predictions is reasonably good. The single design curve of AS/NZS4600 may be unduly optimistic for near-uniform bending and unnecessarily conservative for high-moment gradients in beams of intermediate slenderness. Improvements of the design method of AS4100 are suggested for future design code formulations.
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Information & Authors
Information
Published In
Journal of Structural Engineering
Volume 125 • Issue 11 • November 1999
Pages: 1277 - 1283
History
Received: Nov 11, 1998
Published online: Nov 1, 1999
Published in print: Nov 1999
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