Cold-Formed Steel Lipped Channel Section Columns Undergoing Local-Overall Buckling Interaction

This paper presents an experimental and finite element (FE) investigation into the local-overall buckling interaction behaviour of axially loaded cold-formed steel (CFS) channel section columns. Current design guidelines from the American Iron and Steel Institute (AISI) and the Australian and New Zealand Standards (AS/NZS) recommend the use of a non-dimensional strength curve for determining the axial capacity of such CFS channel section columns. This study has reviewed the accuracy of the current AISI (2016), AS/NZS (2018) and Eurocode (EN 1993-1-3) design guidelines for determining the axial capacity of CFS channel sections under local-overall buckling interaction failure. A total of 40 tests were conducted on CFS channel sections covering stub, short, intermediate, and slender columns with varying thicknesses. A nonlinear FE model was then developed and validated against the test results. The validated FE model was used to conduct a parametric study comprising 70 FE models to review the accuracy of the current design guidelines in accordance with AISI (2016), AS/NZS (2018) and Eurocode (EN 1993-1-3). It was found that the AISI (2016) and AS/NZS (2018) are conservative by 10 to 15% on average when determining the axial capacity of pin-ended CFS channel section columns undergoing local-overall buckling interaction. Eurocode (EN 1993-1-3) design rules were found to lead to considerably more conservative predictions of column axial load capacity for CFS channels.This paper has therefore proposed modifications to the current design rules of AISI (2016) and AS/NZS (2018). The accuracy of proposed design rules was verified using the FE analysis and test results of CFS channel section columns undergoing local-overall buckling interaction.