Material Properties Models for Analysis of Cold-Formed Steel Members

The development and accuracy of an appropriate analytical model to predict the behavior of cold-formed steel (CFS) structural members necessitate a correct representation of the corresponding material characteristics. The results of two series of experimental investigations to evaluate the mechanical properties and the built-in residual stresses of CFS sections are reported in this paper. These investigations were performed on channel-shaped CFS sections manufactured using the cold-roll forming technique. Tensile coupon tests were used to evaluate the mechanical properties at different locations such as flat area, and the corner areas, of the channel sections. Electrical resistance strain gauges with an “electrical discharge machining” cutting technique were used to establish the magnitudes and the distributions of residual stresses within the channel sections. Based on the experimental results, appropriate analysis models for the stress-strain relationship, the variation of the yield strength, and the residual stresses in CFS channel sections have been established. The proposed analysis models for material properties have been incorporated within a large deformation shell finite element to form an analysis model for CFS sections. The efficiency and accuracy of the proposed material properties models have been evaluated by comparing the finite-element analysis results against corresponding experimental results of CFS sections subjected to axial compressive loads.