Experimental vs. theoretical design approaches for thin-walled cold-formed steel beam-columns

The response of thin-walled cold-formed (TWCF) members is significantly influenced by local and distortional buckling phenomena as well as by their interactions with overall instability. Furthermore, because of the frequent use of mono-symmetric cross-section members, their design is often complex and laborious engineering calculations are required, independently of the adopted provisions. With reference to the European (EU) and United States (US) design standards, which are the most commonly adopted worldwide, different alternatives can currently be used: a direct comparison between the predicted load carrying capacities should hence be of great interest for structural engineers and manufacturing technicians. This issue is discussed in the paper, which is focused on isolated TWCF beam-columns. In particular, 5 EU and 2 US alternatives have been discussed focusing attention on the pure theoretical approaches to evaluate the member performance. The applicative part proposes a direct comparison between the associated axial force bending-moment domains investigating the influence of the member slenderness as well as of the moment distribution. Furthermore, these alternatives have been applied to predict the strength of members tested in laboratory for which the behavior of an adequate number of nominally identical specimens has been thoroughly investigated. The proposed statistical re-elaboration of test data, which is comprised of 8 practical cases differing for cross-section sizes, materials and length, for a total of 112 compression tests, allows for defining the experimental design performance to be directly compared with the corresponding one associated with the considered design approaches. © 2019 by The Hong Kong Institute of Steel Construction. All rights reserved.