Tests on Cold-Formed Steel Laced Stub Columns: Axial Strength and Stability Characteristics

The research on cold-formed steel (CFS) built-up columns, which has grown over the past decade, has been instrumental in developing new CFS built-up columns with transversely spaced chords, demonstrating better axial performance than conventional I-type built-up columns. However, previous research findings on CFS laced columns have been limited, with no data available on stub columns. This paper presents the first test program for cold-formed steel laced stub columns using plain channels. The program involved fabricating 12 specimens with a single lacing configuration, connecting lacing elements and end plates to the chords using self-drilling screws, and evaluating the impact of critical parameters on column performance under concentric axial loading. Important variables such as lacing slenderness, end plate length, and transverse chord spacing were examined, with the built-up section's aspect ratio varying from 0.75 to 1.25. The failure modes, peak strengths, and load-displacement curves of the stub column specimens were used to evaluate their performance. In addition, the study compared strength predictions from the current American Iron and Steel Institute (AISI S100-16) and Eurocode (EN1993-1-3) standards against the test strengths. Unlike slender column axial strength, these current standards predicted the axial strengths of the stub columns better, with an overprediction of less than 5%. It was verified that lacing slenderness and end plate length variation does not change the failure mode in CFS laced stub columns. Further, earlier recommendations on end plate length for CFS laced columns cannot be extended to CFS laced stub columns.