Parametric Studies and Design Rules for Local and Distortional Biaxial-Bending Capacity of Cold-Formed Steel Storage-Rack Uprights

This paper first describes a finite element model using advanced analysis to determine the biaxial bending capacity of cold-formed steel storage rack upright sections. The model is found to accurately predict published experimental results with an average predicted to an experimental capacity ratio of 1.02. Second, the validated model is used to run parametric studies and analyze the biaxial response of slender, semicompact and compact unperforated storage rack upright cross sections. Analyses are run for local and distortional buckling failure modes only. Nine biaxial bending configurations are considered per cross section and buckling mode. Results show that a nonlinear interactive relationship typically governs the biaxial bending of the studied uprights. This relationship is discussed and analyzed for the different failure modes and cross-sectional slenderness. The results from the parametric studies are used to verify the accuracy of different forms of published direct strength method (DSM) equations. They consist of the classical DSM equations and the use of inelastic reserve capacity in the DSM with and without using an extended range of the cross-sectional slenderness. Results show that for all investigated buckling modes, the DSM results in better predictions when the inelastic reserve capacity is considered. The appropriate form of the DSM to predict the biaxial capacity of unperforated cold-formed steel storage rack uprights is discussed.