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Strength and deflection behaviour of cold-formed steel back-to-back channels

Pilakoutas, Kypros; Shepherd, Paul; Hajirasouliha, Iman; Mojtabaei, Seyed Mohammad; Ye, Jun

Strength and deflection behaviour of cold-formed steel back-to-back channels Thumbnail


Kypros Pilakoutas

Paul Shepherd

Iman Hajirasouliha

Seyed Mohammad Mojtabaei

Jun Ye


© 2018 Cold-formed steel (CFS) construction can lead to more efficient designs compared to hot-rolled steel members as a consequence of its high strength, light weight, ease of fabrication, and flexibility in their cross-section profiles. However, CFS members are vulnerable to local, distortional and overall buckling modes. This paper develops a numerical model to investigate the flexural strength and failure modes of CFS back-to-back channel beams and verifies the efficiency of an optimisation framework previously proposed. The model incorporates non-linear stress-strain behaviour and enhanced corner properties obtained from coupon tests, as well as initial geometric imperfections measured in physical specimens. To simulate the behaviour of a bolt bearing against a steel plate in the back-to-back section, a connector model is used that takes into account both slippage and bearing deformations. The developed Finite Element (FE) models are verified against six four-point bending tests on CFS back-to-back channel beams, where excellent agreement is found between the experimental results and the FE predictions. The validated FE models are then used to assess the adequacy of the effective width method in EC3 and the Direct Strength Method (DSM) in estimating the design capacity of conventional and optimum design CFS channel beam sections. The results indicate that both EC3 and DSM provide accurate predictions for the bending capacity of lipped channel beam sections. A comparison between FE predictions and tested results show that, the geometric imperfections can change the FE predictions of ultimate capacity by 7%, while the strain-hardening of CFS material at the round corners has negligible effects. It is also shown that EC3 uses a reduced cross-sectional property to calculate deflections, which can reasonably predict deflections with a slight overestimation (6%) at the serviceability load level.


Pilakoutas, K., Shepherd, P., Hajirasouliha, I., Mojtabaei, S. M., & Ye, J. (2018). Strength and deflection behaviour of cold-formed steel back-to-back channels. Engineering Structures, 177, 641-654.

Journal Article Type Article
Acceptance Date Sep 21, 2018
Online Publication Date Oct 21, 2018
Publication Date Dec 15, 2018
Deposit Date Mar 19, 2019
Publicly Available Date Mar 20, 2019
Journal Engineering Structures
Print ISSN 0141-0296
Electronic ISSN 1873-7323
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 177
Pages 641-654
Keywords cold-formed steel, beam, finite element study, strength, deflection
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