DSM-based Design Approach Against Flexural-Torsional and Global-Global Interactive Failures in CFS Columns

Very recently, Dinis et al. (2021) performed a numerical investigation on the post-buckling behavior, strength and Direct Strength Method (DSM) design of cold-formed steel fixed-ended plain (U) and lipped (C) channel columns undergoing global-global (G-G) interaction - a coupling phenomenon involving major-axis flexural-torsional (FMT) and minor-axis flexural (Fm) buckling modes that was first unveiled by Dinis et al. (2020), in the context of fixed-ended U columns. On the basis of the U and C failure load data gathered, a DSM-based design approach for columns buckling in FMT modes that exhibit either pure or G-G interactive collapses was developed and shown to provide accurate, mostly safe and reliable predictions of the experimental (only a few) and numerical and failure loads available. The success of this research effort led the authors to extend its scope to columns (i) with a wide variety of cross-section shapes (return-lip, web-stiffened and web/flange-stiffened lipped channels, lipped zed-sections, hat-sections and rack-sections), cross-section dimensions and lengths, (ii) having various end support conditions (not only fixed-fixed) and (iii) covering wide slenderness ranges. The aim of this work is to report the available results of this ongoing investigation, intended to find an efficient and reliable DSM-based design approach for arbitrary CFS failing in FMT or G-G interactive modes. After a brief overview of the above DSM-based design approach, the paper (i) presents and discusses numerical results concerning the post-buckling behavior and strength of the columns analyzed in this work, and (ii) assembles a fairly extensive set of failure loads - ANSYS non-linear shell finite element analyses are employed. Finally, the numerical failure loads (assembled in this work) are used to assess how the existing DSM-based design approach predicts them and, eventually, propose modifications to improve its performance.

Learning Objectives:
Efficient DSM-based design of cold-formed steel columns failing in flexural-torsional and global-global interactive modes.

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