Generalized direct strength design approach: steel cold-formed columns under buckling mode interaction

Resumo

Thin-walled steel cold-formed members exhibit local (L), distortional (D), and global (G) buckling
modes. These modes can interact in various ways, depending on the relationship between the corresponding
buckling loads (PcrL, PcrD, and PcrG). The direct strength method (DSM) provides equations for designing columns
experiencing global, local, distortional, and local-global buckling interaction (LG). This study focuses on the most

general buckling mode interaction (LDG), building upon a recent approach by the authors that covers local-
distortional buckling (LD). To develop the design equations, extensive numerical (FEM) and experimental

databases were utilized, covering the relevant ranges of slenderness factors (λL, λD, and λG) associated with L, D,
and G buckling modes, respectively. The proposed approach combines the existing DSM equations from the
Brazilian code NBR 14762:2010 and the design equations for LD buckling interaction, recently proposed by the
authors. After identifying the main variables and calibrating the design equations using FEM and literature-based
experimental results, the contribution of the global mode is incorporated. The resulting set of design equations
takes into account all the possible buckling modes, L, D and G, and the buckling interactions (LG, LD, and LDG)
for axial compression of steel cold-formed members.