Bending performance and failure mode of circular hollow section TT-joint connected to ring plates

Abstract

This study focuses on the bending performance of an innovative circular hollow section (CHS) TT-joint connected to ring plates, including the bearing capacity and failure modes. TT-joint specimens with different extended ring-plate widths were designed and tested, and the failure mechanism of the TT-joint was studied from different perspectives, including the failure mode, load displacement, and stress development. A finite element model validated through tests was established, and further 166 finite element models based on dimensionless parameters was carried out, including the diameter-to-thickness ratio of the chord (γ), diameter ratio of the brace to the chord (β), thickness ratio of the brace to the chord (τ₁), thickness ratio of the ring plate to the chord (τ₂), width to thickness ratio of the ring plate (λ), and angle of the braces (θ). The results reveal three typical failure modes of the TT-joints connected to the ring plate with the change in component dimensions, including bulging failure of the chord, buckling failure of the brace, and buckling failure of the ring plate. When the two braces are subjected to uneven loads, the TT-joints are more prone to buckling failure of the brace. All parameters will affect the failure mode of the TT-joints, and the ultimate bearing capacity of the joints decreases as γ increases, and the ultimate bearing capacity of the joints increases with β, τ₁, τ₂, and θ. The parameter λ primarily affects the failure mode and yield bearing capacity of TT-joints and has almost no effect on the ultimate bearing capacity. Finally, a calculation method for the bending capacity of TT-joints was proposed based on the failure mode.