Behaviour and design of cold-formed steel built-up I-beams composed of four channels

• Published in: Journal of constructional steel research 2024-06, Vol.217, p.108671, Article 108671
• Main Authors: Amali, D., Anbarasu, M.
• Format: Article
• Language: English
• Subjects: Built-up beams; Channel section; Cold-formed steel; Direct strength method; Local buckling; Reliability analysis
• ISSN: 0143-974X; 1873-5983
• DOI: 10.1016/j.jcsr.2024.108671

This article presents the detailed results of numerical investigation on the structural behaviour of a novel cold-formed steel (CFS) built-up beams composed of four plain channels arranged together as a closed I-beam, under simply supported end conditions. Finite element (FE) models were developed, validated against existing test results published in the literature. The parametric studies were conducted with main variables: (a) aspect ratio (b) thickness (c) compression flange plate slenderness (d) steel grades and (e) width of flange of flange channels. To analyze to effect of selected factors comprehensively, 168 FE models were studied. Additionally, numerical results were compared with the current DSM in the AISI-S100 Specification to observe the accuracy. The evaluation results reveal that the existing DSM is inadequate to predict the flexural capacity accurately of CFS built-up I-beams composed of four plain channels. Finally, suitable design modifications were proposed, which were also capable of having sufficiently realistic predictions of the flexural strength and behaviour of CFS built-up I-beams and the reliability of the design recommendations was confirmed by means of reliability analysis, which aids in predicting sufficiently realistic complex buckling behaviour of CFS built-up I-beams. •CFS built-up I beam composed of four plain channels under four-point bending were investigated.•Extensive FE parametric analysis on critical factors over a wider range was carried out on a validated FE model.•A novel method to determine the elastic critical buckling stress of CFS built-up I beam was proposed.•A new DSM design equation for accurate strength prediction of CFS built-up I beams was proposed•The reliability of the new proposed equation was verified through a reliability analysis.