Elastic Buckling of Thin-Walled Steel Columns with Periodic Perforations

Finite strip eigen-buckling methods are introduced and validated through finite element eigen-buckling studies for calculating the local, distortional, flexural, and flexural-torsional elastic buckling of open thin-walled steel columns with periodic perforations. The goal in developing these simplified elastic buckling prediction methods is to provide an alternative to often cumbersome thin shell finite element modeling and, in research to come, the tools to accurately predict capacity of cold-formed steel rack sections, including the influence of holes, without the need for physical testing. For local buckling, an elastic plate buckling coefficient is derived with an energy solution considering hole size and frequency. The coefficient, which is lower to reflect the influence of holes on local buckling, is represented as a reduced cross-section element thickness in a finite strip analysis. For distortional buckling, the reduction in transverse web bending stiffness bracing the compression flanges is found to be a function of the planar net and gross areas of the perforated web element and is used to the modify web thickness in a finite strip analysis. For global buckling two viable methods are proposed for calculating the elastic buckling load including hole patterns. The first is a weighted average approach employing the classical cubic buckling equation and the second is simply to multiply the buckling load of the unperforated member by a ratio of the weighted average to gross-section properties of moment of inertia for flexural buckling and the St. Venant torsion constant for flexural-torsional buckling.

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