Dynamic characteristics of a thousands-meter scale cable-stayed bridge

摘要

Some dynamic topics have become of increasing concern for the large bridges' safety. However, precise dynamic characteristics of the bridges are the foundation to solve these topics. In addition, the numerical model can be updated by exact parameters to serve as the baseline model for the following health monitoring and damage detection. This paper describes the experimental and theoretical modal analysis performed on the Sutong Bridge in China, which is the firstbuilt thousand-meter scale cable-stayed bridge in the world. Ambient vibration tests are carried out with dense sensor arrays and the acceleration responses of the deck and the two towers are obtained for processing. Some global vibration modes of the bridge are identified in the frequency range lower than 1.0Hz using both the FFT-based method and the random decrement technique combined with Ibrahim time domain method. The scattering ranges of the extracted modal damping ratios of all modes are narrow and the results contribute to the following research. Theoretical analysis is conducted on the three-dimentional finite element model developed from the design drawings combined with some measured material properties. A good correlation is achieved between the theoretical and the experimental analysis. So the main assumptions adopted in the FE model for dynamic analysis are assessed and summarized. Based on the study, some useful guidelines for dynamic analysis are presented.