Buckling Strength of Axially Loaded Cold Formed Built-Up I-Sections

This paper presents a numerical procedure using finite element analysis for the calculation of axial strength of cold formed steel built-up I-sections composed of two back-to-back channels. The material nonlinearity of the flat and corner portions of the section were incorporated in the model. The effects of initial local and overall geometric imperfections as well as the membrane residual stresses have been taken into consideration in the finite element model. The results of the nonlinear finite element analysis were compared with the available experimental results, and with the calculated theoretical buckling capacities based on the AISI design provisions. A parametric study was carried out using the developed finite element model to study the effects of member and cross-section geometries and imperfection values on the strength of cold-formed steel built-up I-columns. The column strengths predicted from the parametric study were compared with the design strengths calculated using the American Specification. The results of the parametric study showed that the design provisions specified in the American Specifications are generally conservative for long and medium length columns, but may give un-conservative estimates for some of the short columns.

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