Research Spotlight: On the Distortional-Global Interaction in Cold-Formed Steel Columns: Relevance,

2017 Annual Stability Conference Presentation

Session SS2A: Technical Presentations: Stability of Thin-Walled Columns Tuesday, March 21, 2017 3:15 pm

On the Distortional-Global Interaction in Cold-Formed Steel Columns: Relevance, Post-Buckling Behavior, Strength and DSM Design

This work reports results of an ongoing numerical (shell finite element) investigation on the relevance, post-buckling behavior, strength and design of fixed-ended cold-formed steel columns undergoing distortional-global (D-G) interaction. The columns analyzed exhibited three cross-section shapes, in order to study distinct natures of D-G interaction, which may involve distortional and (major-axis) flexural-torsional buckling (plain and web-stiffened lipped channel columns), or distortional and (minor-axis) flexural buckling (Z columns). The occurrence of different types of D-G interaction, namely “true D-G interaction” or “secondary-(distortional or global) bifurcation D-G interaction” are investigated for each of the aforementioned D-G interaction natures. The results presented concern columns with various geometries and yield stresses, ensuring a wide variety of combinations between (i) global-to-distortional critical buckling load ratios and (ii) squash-to-non critical buckling (distortional or global) load ratios. Then, the numerical failure load data obtained are compared with their predictions by (i) the current DSM (Direct Strength Method) column global and distortional design curves, and (when necessary) (ii) proposed DSM-based design approaches, developed to handle D-G interactive failures.

André Dias Martins, Dinar Camotim, and Pedro B. Dinis, University of Lisbon, Lisbon, Portugal

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