Tests and Analyses of Nonorthogonal Hollow Joints in Cable-Stayed Bridges under Cyclic Loading

Cable-stayed bridges usually employ diamond-shaped or Y-shaped RC towers. Different from classical solid RC beam–column joints, nonorthogonal hollow joints (NOHJs) may deliver unique damage features under transverse earthquakes. In this study, five NOHJ specimens with different beam–column angles are designed and tested to investigate their damage patterns and load-carrying capacities. The test results indicate that the joint zones suffer from concrete cracking and reinforcement yielding. Ultimate failure occurs at the end section of the brace beam, which is the controlling section for the load-carrying capacity. The hysteresis curves of the NOHJ specimens show evident asymmetry because of the beam–column angle, which introduces an initial moment at the brace beam end. A simple analytical model is proposed to estimate the yielding and peak loads. In addition, a sophisticated numerical model showing good agreement with the test results is developed using ABAQUS (version 6.14). The damage evolution mechanism of the joint zone is quantitatively discussed based on the numerical analysis, and a parametric analysis is then performed to verify the influence of the beam–column angle, the aspect ratio of joint zone, and other parameters. Finally, a regressed model for predicting the cracking and yielding loads of the joint zone is developed using the random forest method.