Local Buckling Expressions for Lipped Channels

This paper develops empirical closed-form equations for local buckling of cold-formed steel lipped-channels under four conditions: pure compression, major axis bending, minor axis bending of the web, and minor axis bending of the lip. A series of semi-analytical finite strip method simulations are conducted and the local plate buckling coefficients for the cross-section are determined from these simulation results. Empirical closed-form equations are developed by curve-fitting to the simulated local plate buckling coefficients. The coefficients are expressed in a manner for convenient use in cold-formed steel design specifications such as AISI S100. The relationships between the plate buckling coefficients and the following ratios: web depth to flange width, lip length to flange width, and web depth to lip length are explored. The developed equations provide a simpler alternative to performing simulations when developing the local buckling of lipped channels in AISI S100. In ongoing work, closed-form equations for additional cold-formed steel shapes, such as zee sections and hat sections, will be generated.

Learning Objectives:
Explain the differences in local buckling behavior for lipped-channels that are placed under (a) pure compression, (b) major axis bending, (c) minor axis bending of the web, or (d) minor axis bending of the lip.

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