Direct Strength Approach for Local Buckling of Cold-Formed Steel Built-Up Beams with Slender Unstiffened Flange Elements
Publication: Practice Periodical on Structural Design and Construction
Volume 26, Issue 3
Abstract
The behavior of cold-formed steel (CFS) built-up members is fascinating, and owing to its advantages, the necessity of using built-up members is increasing in construction practice. However, as per the current design specifications of the American Iron and Steel Institute (AISI), there is no explicit design method for CFS built-up members. The objective of this investigation is therefore to examine the appropriateness of using the current AISI design method for CFS open or single cross-section members toward the design of built-up members with slender unstiffened flange elements subjected to bending. The investigation results indicate that the previously suggested design procedure (built-up elastic buckling model with double flange element) results in unconservative design predictions compared to the experimental results ( versus ). The reason for the unconservative design prediction by AISI expression with the previously suggested procedure is due to the overestimation of the critical elastic local buckling stress and incorrect failure mode prediction of the built-up cross section, which is a key input to the direct strength method (DSM). Hence, modified design equations and procedures are suggested for the CFS built-up beams with slender unstiffened flange elements. The modified design procedure is formulated from the investigation of failure modes. It is also shown that the newly proposed design equation with the suggested procedure for determining the local buckling stress for slender unstiffened flange elements is reliable.
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Data Availability Statement
Some or all data and photographs of the failure modes, i.e., full-scale specimen and sheathing fastener connection and analysis models, used during the study are available from the corresponding author by request.
Acknowledgments
The investigation reported in this paper was funded by the Science Engineering and Research Board (SERB) Research Grant No. SB/S3/CEE/046/2014 from the Department of Science and Technology (DST), Government of India. The first author would like to acknowledge the financial assistance received from this project.
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© 2021 American Society of Civil Engineers.
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Received: Oct 30, 2020
Accepted: Mar 29, 2021
Published online: Jun 1, 2021
Published in print: Aug 1, 2021
Discussion open until: Nov 1, 2021
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