Distortional Buckling of Cold-Formed Steel Members

Cold-formed steel members are widely employed in steel construction because they are lighter and more economical than traditional hot-rolled ones. Nowadays, the easy availability and accessible cost of high-strength low-alloy steels, weathering steels, and zinc-coated steels have led to members with high width/thickness ratios, rendering them even more susceptible to local buckling and to another buckling mode called distortional buckling, affecting mainly members with edge stiffeners (lipped channels, Z sections, hat, rack, etc.). Hence, current versions of technical codes for cold-formed steel design have warned about the importance of this phenomenon, outlining procedures to evaluate member strength based on distortional buckling, e.g., the simplified model of the Australian/New Zealand Standard AS/NZS 4600 proposed by Lau and Hancock, also adopted by the Brazilian Standard NBR 14762. In this study, an analysis is made about lipped channels under compression and bending, comparing the results obtained through the Brazilian Standard simplified model against those of the elastic analysis via the finite strip method, evaluating the conformity and the range of validity of the simplified model application.