Tubular members are widely used in structural applications such as trusses, frames and lattice towers, where joints play a crucial role in transferring loads effectively. The purpose of this study is to evaluate the structural performance of cold-formed steel (CFS) T-joints with square tubular sections (STS) under combined axial compression and bending. By focusing on enhancements through side-plate reinforcement, the study examines the impact of reinforcement on joint strength, load capacity, stiffness and failure delay.
The study involves experimental testing of six CFS T-joints with a brace-to-chord width ratio of unity, fabricated through automatic gas metal welding. To enhance load capacity, stiffness and delay joint failure, side plates of varying lengths were welded at the brace-chord junction. Performance indicators – maximum load, stiffness and deformation at failure – were analysed. A numerical analysis explored the influence of critical ratios, such as brace-to-chord width and thickness, on joint strength. Comparative assessments with Eurocode 3 (EC3) and CIDECT predictions highlighted inadequacies, leading to proposed amendments in CIDECT incorporating a reduction factor, validated through reliability analysis.
Current predictions of joint strength by EC3 with and without considering the reduction factor, as well as CIDECT without considering the reduction factor, were found to be inadequate in accurately predicting the joint strength of CFS square tubular T-joints reinforced with side plates. Finally, this study proposes amendments to be incorporated into CIDECT, accounting for a reduction factor to enhance the accuracy of predicting T-joint strength. Furthermore, the reliability of these proposed changes was confirmed through rigorous reliability analysis.
This study provides valuable insights into the behaviour of CFS T-joints with STS under combined axial compression and bending – an area with limited existing research. By incorporating side-plate reinforcements, the study demonstrates enhanced load capacity, stiffness and delayed failure in T-joints, offering a novel approach to improving joint performance. Additionally, it critically examines and identifies inadequacies in current strength prediction models (Eurocode 3 and CIDECT), proposing a modified CIDECT approach with a reduction factor for better accuracy. These findings offer valuable contributions to the design and application of reinforced CFS T-joints in structural engineering.
