Effect of Geometric Parameters (β and τ) on Behaviour of Cold Formed Stainless Steel Tubular X-Joints

CIDECT guideline of carbon steel is frequently applied to design the cold-formed stainless steel tubular X-joints. The allowable range of the brace to chord width ratio (β) had been recorded in this guideline without mention to specific limits for the brace to chord thickness ratio (τ). Therefore, this study was carried out to investigate the effect of β and τ ratios on the behaviour of tubular X-joints by using LUSAS software. Three numerical models were created based on the stainless steel sheet type which symbolled as XD (duplex EN1.4462), XH (high strength austenitic), and XN (normal AISI 304). A good consistency was achieved with the experimental test in terms of load–deflection behaviour, ultimate joint strength, and failure modes within a maximum error of 8.63%. Parametric studies results indicated that the increased of (β) ratio at constant (τ = 1) capable to increase the joint strength which was quite conservative with the CIDECT design strengths of specimens failed with the chord side wall failure, while it was unconservative to chord face failure. Hence, equations were proposed to calculate the joint strength for specimens failed by chord face failure. A range of (0.4–2) had proposed for (τ) ratio. The ultimate joint strength obviously increased at high values of (τ) ratio within a constant value of (β = 1). Moreover, the chord side wall and brace local buckling failure modes observed when (τ > 0.5) and (τ ≤ 0.5), respectively, which indicated that the brace local buckling failure can be only occurred when (β > 0.85) and (τ ≤ 0.5).