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

This article presents the detailed results of numerical investigation on the structural behaviour of a novel coldformed 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 builtup 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 Ibeams 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.