Fang, ArthurDivi, Seshagiri Rao2024-10-282024-10-282024https://hdl.handle.net/10289/17001The use of cold-formed steel (CFS) gapped back-to-back channel sections is becoming popular, especially in New Zealand and South-East Asia. Introducing a gap between the back-to-back channels enhances resistance to lateral-torsional buckling. Previous research has investigated gapped built-up channel sections with spacers but hasn't determined the optimal number of spacers relative to length. Also, little attention has been given to how transverse spacing affects the axial capacity of these sections. This study fills those gaps by developing and validating a non-linear elastoplastic finite element (FE) model against experimental data. A parametric study of 1000 FE models examine the effects of column length, CFS section thickness, materials properties, and spacer spacing, on the axial capacity of gapped built-up columns. Key findings include: (1) Up to a column length of 4000 mm, three equally spaced spacers optimize compressive strength in gapped sections. (2) Optimal transverse spacing aligns with the channel web depth, offering no significant strength increase beyond 1.5 times the web depth. (3) Gapped sections show a substantial average increase (424%) in compressive strength over single-channel configurations, and a moderate improvement (125%) compared to non-gapped built-up sections. (4) FEA results closely match the predictions of AS/NZS4600:2018, differing by only 5% in compressive strength.enAll items in Research Commons are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.Thesis