Environment Inspired By The Bridge Structure Modal Parameter Identification Methods

Bridge structural modal parameter identification is the important content of the modal analysis. Traditional modal parameter identification methods require artificial excitation by large equipment, which affect the normal operation of the structure. However, the modal parameter identification methods under ambient vibration like wind load, earth pulsation, vehicle exciting, etc. only need response signals, without imposing excitations on the structure, which can save labors and equipment costs, and avoid potential damage to the structure. So the modal parameter based on ambient vibration has been adopted extensively in engineering applications. In this paper, modal parameter identification method by ambient excitation is studied. The main work and research contents are as following:1. Comprehensively elaborate the important role of the structure modal parameter identification under ambient excitation in engineering application. Domestic and international research situation in the field is reviewed. Typical modal parameter identification methods based on ambient excitation are briefly introduced.2. The paper focuses on the theory and application of the NExT/ERA method under ambient excitation. The NExT/ERA method exerts each advantage of natural excitation technique (NExT) and eigensystem realization algorithm (ERA) in identifying the structure modal parameter under ambient excitation. Based on the platform of MATLAB, the program of NExT/ERA method is compiled to identify modal parameters. The simply supported beam of concrete is simulated by this method. The results show the validity and anti-noise property of NExT/ERA method.3. A cantilever beam is used in the vibration test. Modal parameters are identified from the measured acceleration responses by NExT/ERA method, and compared with the theoretical values. It is indicated that the NExT/ERA method is feasible in practice. 4. Build the 3-dimensional finite element model of the Nanjing Yangtze River Bridge using finite element software ANSYS. Earth pulsation is loaded to the model to obtain the response signals. With NExT/ERA method the structural modal parameters are identified. The identified modal parameters are compared with those obtained by finite element analysis. The feasiblity and effectivity of NExT/ERA method are verifed in practical engineering applications of bridge.