Direct strength prediction of cold-formed steel fixed-ended singly-symmetric columns buckling in flexural–torsional modes

• Published in: Thin-walled structures 2023-06, Vol.187, p.110730, Article 110730
• Main Authors: Cerqueira, Elisa, Landesmann, Alexandre, Camotim, Dinar, Dinis, Pedro B., Martins, André D.
• Format: Article
• Language: English
• Subjects: CFS fixed-ended singly-symmetric columns; Direct Strength Method (DSM) design; Flexural–torsional and interactive global failures; Flexural–torsional buckling; Flexural–torsional/flexural interaction; Shell finite element analysis
• ISSN: 0263-8231; 1879-3223
• DOI: 10.1016/j.tws.2023.110730

The work reported in this paper is a sequel of previous numerical investigations carried out by the authors on the post-buckling behaviour, strength and Direct Strength Method (DSM) design of cold-formed steel (CFS) fixed-ended plain and lipped channel columns (both singly-symmetric with respect to the major-axis) buckling in flexural–torsional modes and experiencing global-global interaction – a coupling phenomenon involving major-axis flexural–torsional (FMT) and minor-axis flexural (Fm) buckling that was first unveiled in those studies. In the specific context of plain and lipped channel columns, a DSM-based design approach for columns buckling in FMT modes and failing in either pure FMT or FMT-Fm interactive modes was developed and shown to provide accurate, mostly safe and reliable predictions of the experimental (only a few) and numerical failure loads available. The success of this research effort encouraged the authors to extend the scope of the investigation to fixed-ended columns with other singly-symmetric cross-section shapes, namely return-lip, web-stiffened and web/flange-stiffened lipped channels, hat-sections and rack-sections (deemed representative of any arbitrary singly-symmetric cross-section). The results attained during this investigation are presented and discussed in detail – they concern the post-buckling behaviour, strength and DSM-based design of the columns analysed, including fairly extensive failure load sets (Ansys non-linear shell finite element models are used to obtain them). The main output of this work is a DSM-based design approach for arbitrary CFS fixed-ended singly-symmetric columns exhibiting pure FMT or FMT-Fm interactive failures. •Major-axis flexural–torsional (FMT) - minor-axis flexural (Fm) interaction in CFS columns.•Fixed-ended singly-symmetric columns buckling in FMT modes and failing in FMT-Fm interactive modes.•Numerical investigation of 1200 columns with several geometries, yield stresses and interaction levels.•Column buckling and post-buckling (elastic and elastic–plastic) behaviour under FMT-Fm mode interaction.•DSM-based design against FMT (pure) or FMT-Fm (interactive) failure of columns buckling in FMT modes.