Strength enhancements in cold-formed structural sections — Part I: Material testing

This paper describes a material test programme carried out as part of an extensive study into the prediction of strength enhancements in cold-formed structural sections. The experiments cover a wide range of cross-section geometries – twelve Square Hollow Sections (SHS), five Rectangular Hollow Sections (RHS) and one Circular Hollow Section (CHS), and materials – austenitic (EN 1.4301, 1.4571 and 1.4404), ferritic (EN 1.4509 and 1.4003), duplex (EN 1.4462) and lean duplex (EN 1.4162) stainless steel and grade S355J2H carbon steel. The experimental techniques implemented, the generated data and the analysis methods employed are fully described. The results from the current test programme were combined with existing measured stress-strain data on cold-formed sections from the literature and following a consistent analysis of the combined data set, revised values for Young’s modulus E and the Ramberg-Osgood material model parameters n, n' 0.2,u and n'0.2,1.0 are recommended. A comparison between the recommended values and the codified values provided in AS/NZS 4673, SEI/ASCE-8 and EN 1993-1-4 is also presented. The test results are also used in a companion paper for developing suitable predictive models to determine the strength enhancements in cold-formed structural sections that arise during the manufacturing processes.