Buckling mode interaction in cold-formed steel (CFS) members must be considered for the structural design, which may lead to a significant reduction of the structural strength, usually recognized as erosion of the limit load. So far, the distortional-global (DG) buckling interaction is not covered by codes, e.g. Brazilian code NBR 14762:2010. The present investigation is aimed at the DG interaction of CFS lipped channel (LC) columns, which is the most usual section. The methodology evolves a parametric analysis, over a single LC column under DG buckling interaction. First, a study of initial geometric imperfection (IGI) sensibility is performed, with the purpose of understanding the influence of the IGI on the column’s behavior. Moreover, the parametric analysis is extended to a set of yielding stress and column lengths, to understand the ultimate load under different types of DG buckling interaction natures. Conclusions on this research have been shown that the actual global buckling equation from the Direct Strength Method is already suitable to cover the DG buckling interaction for the case of lipped channel columns.

The objective of this research is to present practical solutions for improving structural performance of thin-walled conic polygonal monopoles. The analysis encompasses computational simulations, analytical evaluation, and structural verification of reinforcements for openings and longitudinal folded stiffeners of flat walls. A benchmarked solution is derived from a design involving a 20-sided cold-formed steel polygonal section employed to support telecommunication antennas at a height of 40 meters. The structural verification is performed under the influence of wind loads, with particular attention to the commonly reported basic gust wind speed in Brazil. The conducted analysis encompasses: (i) wind-induced static equivalent dynamic behavior, (ii) parametric elastic buckling analysis, (iii) non-linear finite element analysis of reinforced openings, and (iv) direct strength method (DSM) performance evaluation of stiffened polygonal cross-sections. The importance of combining tailored numerical tools such as the finite strip and finite element methods, as well as wind-induced behavior, is demonstrated through the structural analysis results. In essence, the study's findings reveal the previously overlooked local-distortional buckling interaction in current design guidelines. Moreover, the research demonstrates that incorporating reinforcements and longitudinal stiffeners significantly enhances the flexural capacity of slender structures. Notably, the adoption of a single 4-fold (trapezoid) stiffener shape, per polygonal wall, emerges as a promising effective solution for enhancing the overall flexural capacity. Further full scale experimental structural tests and computational fluid dynamics should be considered for advanced structural analysis and improved design.