Design of Cold-Formed Steel Built-Up Back-to-Back Columns Subject to Local-Flexural Interactive Buckling
Publication: Journal of Structural Engineering
Volume 149, Issue 12
Abstract
The North American Standard (NAS) and the European Standard (EC3) for cold-formed steel design provide limited guidelines for the strength predictions of built-up columns. The existing design equations are limited to flexural buckling and local-flexural interactive buckling. The present study evaluates the local-flexural interactive design equations for cold-formed steel built-up back-to-back I-section columns against the results of experimental and numerical studies. The results show that the existing design guidelines for local-flexural interactive buckling are unconservative by about 17%, 5%, and 15% for DSM-NAS, EWM-NAS, and EWM-EC3, respectively. Furthermore, a maximum reduction in the built-up column strength by local-flexural interaction is observed when its nominal local and flexural buckling loads are close. Based on the results and observations, new design equations are proposed by including the product of nominal local and flexural buckling loads for the North American and European standards, which capture the local-flexural interactive buckling in built-up I-section columns. The effect of fastener spacing on the ultimate load for local-flexural interactive buckling is also evaluated, and its effect is found to be small, unlike for global buckling. The minimum fastener spacing criteria of NAS are assessed, and suitable recommendations are provided for fixed-end columns. Overall, the present study provides insights into the local-flexural interactive buckling behavior of built-up I-section columns and proposes reliable design equations to predict the ultimate load.
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Data Availability Statement
Some or all data, models, or code that support the findings of this study are available from the corresponding author upon reasonable request.
Acknowledgments
The authors thank the Indian Institute of Technology Madras (India) and Queensland University of Technology (Australia) for providing financial support and the research infrastructure facilities for the research work reported in this paper.
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Published In
Journal of Structural Engineering
Volume 149 • Issue 12 • December 2023
Copyright
© 2023 American Society of Civil Engineers.
History
Received: Apr 15, 2023
Accepted: Jul 31, 2023
Published online: Oct 9, 2023
Published in print: Dec 1, 2023
Discussion open until: Mar 9, 2024
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