Faculty Publications
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Item Local buckling behaviour of web perforated cold-formed steel lipped channel columns(Elsevier Ltd, 2024) Shabhari, A.; Jeyapragasam, V.V.K.; Chandrasekar, D.To connect beams and bracings with storage rack uprights, closely spaced perforations are provided along the web, flanges, and rear flanges of uprights. These perforations can significantly lower the ultimate capacity of such compression members with the possible influence of its natural buckling modes. This capacity reduction can depend on various parameters such as (a) geometrical shape, proportioning of cross-section, and stiffeners; (b) perforation shape, size, spacing, and location; (b) slenderness of member, cross-section, and elements of cross-section; and (d) material properties. A thorough understanding of the influence of the above-mentioned factors is necessary for the accurate strength prediction of perforated Cold-formed steel (CFS) compression members. Even though the current design standards are updated for the accurate strength prediction of unperforated CFS compression members, they do not collectively account for the influence of all the aforementioned factors on the load-carrying capacity of the perforated CFS members, particularly for the local buckling capacity. Though the Direct Strength Method (DSM) of design is the most accepted method for accurate strength prediction of CFS members even for complex cross-sectional shapes, recent research on the strength evaluation of perforated CFS members using DSM has emphasized the need for refinement in DSM. The Modified Direct Strength Method (MDSM), which accounts for the simultaneous buckling of flanges and web, includes the cross-section aspect ratio and cross-section slenderness to predict more accurately the local buckling design strength. However, it was developed only for unperforated specimens. Hence, a systematic experimental and numerical investigation was done to understand the influence of the perforation in the local buckling behavior of the lipped channel section. In total, 14 specimens, including 2 unperforated and 12 web perforated CFS lipped channel stub columns were physically tested with fixed support conditions. The Finite Element Analysis using ABAQUS software was used to conduct an extensive parametric numerical study. The results were used to compare the strength curves of DSM and MDSM and the modification in the design curves has been proposed by considering the erosion in strength due to the presence of perforation. © 2024 Elsevier LtdItem Local buckling strength enhancement due to non-slender flanges in web perforated plain channel columns(Elsevier Ltd, 2025) Francis, R.; Shabhari, A.; Jeyapragasam, V.V.K.; Chandrasekar, D.Cold-formed steel columns are the primary compression members in housing and industrial storage racks, with discrete holes or closely spaced web perforations. The element slenderness and web perforations influence the local buckling capacity. This study examines the local buckling capacity of slender web plain channel cross-sections with non-slender or slender flanges in the presence of web perforations. Fourteen plain channel stub column tests were conducted on two cross-section aspect ratios, two perforation shapes, with three perforation orientations. Further, a comprehensive parametric study was conducted using validated Finite Element models. The local buckling strength of unperforated and web-perforated cold-formed plain channel columns is evaluated using the Direct Strength Method (DSM) and Modified Direct Strength Method (MDSM). The increase in local buckling strength due to non-slender flanges becomes significant, depending on the aspect ratio and non-dimensional local buckling slenderness ratio of the plain channel cross-section. This research provides the scope to expand the applicability of DSM and MDSM design strength predictions from cold-formed steel design to general thin-walled steel sections, where the welded thin-walled steel sections can have different element thicknesses. As the element thickness plays a crucial role in element slenderness and inter-element interaction, the local buckling capacity prediction available for uniform cross-section thickness can be unduly conservative. This study highlights the significance of element slenderness and effective area reduction due to perforation shape and orientation in the local buckling strength of cold-formed plain channel sections. © 2025 Institution of Structural Engineers. Published by Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.