Impact of global flexural imperfections on the cold-formed steel column curve

摘要

Due to inherent complications in manufacturing and installation global out-of-straightness imperfections in cold-formed steel columns may sometimes be greater than L/960, which is the maximum amount assumed in North American cold-formed steel design specifications. The correction that should be applied to currently used column design curves to account for imperfections larger than L/960 is unknown. To find this correction the strength of typical cold-formed steel columns with explicit imperfections is determined using a geometric and material nonlinear beam finite element solution, and a closed-formed solution. The closed-formed solution is shown to agree well with the finite element solution and accurately recreates the current design specification column curves at the L/960 imperfection level. The closed-formed solution is used as the basis for predicting reductions in the nominal column stress for columns with imperfections that are greater than L/960. The developed solution is recommended in design for those situations in which large out-of-straightness imperfections are encountered.