DSM Design of CFS Lipped Channel Columns undergoing Distortional-Global Interaction at Elevated Temperatures

This work reports the results of an ongoing numerical investigation dealing with the post-buckling behavior, strength and DSM (Direct Strength Method) design of fixed-ended cold-formed steel (CFS) lipped channel (LC) columns experiencing distortional-global (flexural-torsional) (D-FT) interaction at elevated temperatures caused by fire conditions. It extends the scope of the parametric study recently reported by Ferreira Filho et al. (2022), by obtaining a fairly extensive additional set of numerical failure loads, covering wider (i) cross-section dimensions and (ii) interaction D-FT types and levels -- this is done by means of ABAQUS shell finite element GMNIA, using models previously developed by the authors and adopting an EC3-based (2005) model to describe the temperature-dependence of the CFS material properties. The whole set of assembled failure load data is then used to search for an efficient DSM-based design approach to predict them. The starting point of this search is provided by the combination of the strength curves developed by Landesmann et al. (2019) and Bicelli et al. (2021), following the idea first put forward by Schafer (2002) and later used by Martins et al. (2018) -- however, these authors only considered columns at room temperature and used the currently codified DSM column global design curve. On the basis of the findings reported in this work, it is possible to draw a few conclusions that provide (i) clues to reach a more efficient DSM-based design approach and (ii) encouragement to extend the current research effort to columns with other cross-section shapes and/or support conditions, aimed at achieving a safe, economic and reliable general DSM-based design approach for CFS columns failing in D-FT interactive modes at elevated temperatures.

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