calculating the nonlinear stiffness and ultimate strength of tube–gusset plate joints in circular hollow sections

Tube-gusset plate joints (tgpjs) play a significant role in tower structures. however, there is limited literature on calculation methods for the nonlinear stiffness and generic bearing capacity of these joints. to address this gap, this study employs full-scale tests, numerical simulations, and theoretical analyses to investigate tgpjs. the load transmission path and failure mechanism of the joint are elucidated by discretizing the joint chord. the joint primarily relies on the ring beam for load transmission until it reaches the limit state. after the ring beam loses its bearing capacity, the busbar beam continues to support the joint. a calculation model for the elastic stiffness and ultimate bearing capacity of the ring beam is formulated, considering the constraint effect of the busbar beam. furthermore, the stiffness and limit state of multiple ring beams under cooperative loading are numerically analysed. the interaction mechanism of ring beams under cooperative loading is clarified, highlighting a decrease in stiffness and ultimate bearing capacity from the edge to the centre. the nonlinear stiffness and ultimate bearing capacity formulas for ring beams under cooperative loading are derived by fitting correction coefficients to the existing calculation method. finally, an overall mechanical performance analysis model for tgpjs is established by incorporating a nonlinear stiffness spring support within the rigid beam spring support model. a comparison of the theoretical calculation results and numerical analysis values verifies the accuracy and feasibility of the proposed method for predicting the nonlinear stiffness of joints. © the author(s), under exclusive licence to the iran university of science and technology 2023.