Buckling and Strength of Cold-Formed Thin-Walled Built-Up Columns under Axial Compression: Tests and Code Evaluation

Fei Yang; Xingkui Yang

doi:10.46604/ijeti.2026.15850

Authors

Fei Yang Shanxi Polytechnic College, Shaanxi, China
Xingkui Yang Shanxi No. 6 Construction Group Co., Ltd., Shaanxi, China

DOI:

https://doi.org/10.46604/ijeti.2026.15850

Keywords:

cold-formed thin-walled steel, built-up sections, axial compressive capacity, design methods

Abstract

This study examines the axial-compression behaviour of cold-formed thin-walled steel built-up columns. Sixty concentric axial tests are carried out on six cross-section configurations (single C- and U-sections and four screw-fastened built-up sections) with lengths from 500 to 3000 mm. The measured capacities are compared with predictions from the Chinese code GB 50018-2002 using the Effective Width Method (EWM) and from AISI S100-2007 using both EWM and the Direct Strength Method (DSM). For closed multi-limb built-up sections, members with slenderness λ < 70 failed mainly by local buckling, whereas λ > 70 led to global buckling. For open built-up sections, λ < 80 is governed by distortional buckling and λ > 80 by global buckling. Overall, GB EWM provided the closest strength predictions for the built-up members, while AISI DSM is generally conservative. The results offer practical guidance for the design of cold-formed steel built-up compression members.

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