Strength of external-ring-stiffened tubular X-joints subjected to brace axial compressive loading

This paper presents the results of numerical and analytical studies to obtain ultimate strength enhancement coefficient (R _e ) equations for external-ring-stiffened circular hollow section (CHS) X-joints under axial compression. The FE modeling approach is validated by the results of axial compressive experiments conducted in the authors’ previous research on six X-joints with and without stiffeners. In all, 160 unstiffened and ring-stiffened FE models of CHS X-joints subjected to brace axial compression were investigated. The effects of the brace-to-chord diameter ratio β the ratio of chord diameter to twice the chord wall thickness γ the stiffening ring width factor β _r (i.e. 2b _r /d ₀ where b _r is the ring width and d ₀ is the chord diameter), and the stiffening ring thickness factor τ _r (i.e. t _r /t ₀ where t _r is the stiffening ring thickness and t ₀ is the chord wall thickness) on the structural behavior of external-ring-stiffened CHS X-joints were evaluated. Parametric analysis showed that the ultimate strength enhancement coefficient R _e decreased with the increase in the diameter ratio between the brace and the chord β but once β exceeded 0.4, the effect on R _e was slight. Furthermore, the ratios of chord diameter to twice the chord wall thickness γ the stiffening ring width factor β _r , and the stiffening ring thickness factor τ _r were all positively correlated with improvement in the ultimate strength of the external-ring-stiffened CHS X-joints. An analytical formula based on the yield volume model was derived to predict the ultimate strength enhancement of external-ring-stiffened X-joints.