Design Models for Thin-Walled Sections in Bending Containing Unstiffened Elements (No. R820)

Abstract

This report presents a general design procedure for calculating the moment capacity of sections containing unstiffened elements under stress gradients. The method uses the design equations for calculating both elastic and plastic effective widths of unstiffened elements under stress gradients, based on plate test results, presented in a companion report. Current international design provisions allow the capacity of sections that contain unstiffened elements under stress gradients to be calculated on the basis of initiation of yielding in the section. This report presents non-iterative methods for the calculation of the capacity, when both elastic and plastic effective width equations are used to establish the effective section. The methods are shown to be in good agreement with experimental data of I-sections and plain channels in minor axis bending. Particular attention is given to the effect of both the elastic buckling coefficient used in the effective width method, and the use of inelastic considerations, on the bending capacity of sections that contain unstiffened elements under stress gradients. Specific design proposals are presented in the form of amendments to the current Australian standard for cold-formed steel structures.