Effect of unsupported chord slenderness on the buckling strength and stability response of CFS battened columns

Limited tests on cold-formed steel (CFS) battened columns (with channel chords) have revealed that the unsupported chord slenderness has a significant impact on the performance of battened columns. Furthermore, it was suggested that the relative slenderness of the unsupported chord should not exceed 0.25, if the current codes for the design of CFS members were to be adopted for strength predictions. However, it needs to be substantiated properly, as few test results were used to bring out this recommendation. This study deals with a numerical investigation on the role of unsupported chord slenderness, chord compactness and overall slenderness, on the axial strength and deformation behaviour of battened columns composed of unstiffened channels. Two plain CFS channels with adequate transverse gap to achieve the cross-sectional aspect ratio as unity, were connected in toe-to-toe arrangement using batten plates to form closed built-up sections. Special emphasis was put on the influence of unsupported chord slenderness on the buckling strength and stability response of battened columns. For each overall column slenderness, three zones of relative unbraced chord slenderness, i.e., 0.25, 0.5 and 0.75 were investigated. The numerical model was adequaltely validated against the test results on battened columns available in the literature, before conducting the extensive parametric study. The numerical analysis will generate a wide pool of data points to be used for checking the adequacy of the current codes, and bringing out the revised value for the relative slenderness of the unsupported chord, if necessary, for safe strength predictions.

Learning Objectives:
Adequacy of the unsupported chord slenderness.

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