Ultimate strength of multiplanar KT-type tube–gusset plate joint with half-ring stiffener plates

Abstract

In this study, full-scale tests, numerical simulations, and theoretical analyses on double KT (DKT)-type tube–gusset plate joints (TGPJs) stiffened with half-ring stiffener plates were performed. The failure modes and mechanisms of DKT-TGPJ under the opposing action of multiplanar loading (e.g., compression vs. tension) were determined to comprise ‘chord failure’, ‘stiffener plate failure’, and ‘combined failure’. The incidence of each failure mode was clearly related to the stiffness of the stiffener plate. When the stiffener plate had low stiffness, the TGPJ exhibited ‘stiffener plate failure’; when the stiffener plate had high stiffness, the TGPJ exhibited ‘chord failure’; and lastly, when the stiffness of stiffener plate is moderate, the TGPJ exhibited ‘combined failure’. A method for calculating the ultimate bearing capacity in the case of stiffener plate failure was proposed based on the yield-line theory. According to the deformation mode of TGPJ in the case of chord failure, a leverage model was established, and a method for calculating the ultimate bearing capacity was obtained. The minimum value obtained from the above two methods was taken as the ultimate load bearing capacity of DKT-TGPJ, which was subsequently verified against the test and finite element model results. The proposed bearing capacity calculation method was shown to reproduce the test and numerical analysis results more accurately than the Japanese and Committee for International Development and Education on Construction of Tubular Structures (CIDECT) codes.