Research On Modal Parameters Identification And Application Of Bridge Structure

The safety of the bridge is closely related to people's lives and property. Therefore, it is particularly important to test the dynamic characteristics of bridge, to detect the changes in structural parameters of bridge and then to build the detection system of bridge. During bridge's sevrice, the bridge will usually have different degrees of damage which is suffered from various natural disasters and human artificial destorying. The injury will not only increase the aging of bridge and reduce the load carrying capacity of bridge, but also affect the safe operating of bridges. Therefore, a warning and timely maintaining systme based on identifying the modal parameters and then inspecting damage of the bridge structure is developed in this study, which will contribute to eliminate hidden dangers and to avoid catastrophic accidents.Based on the study of Chaobai River bridge, a benchmark theoretical model of bridge structure was established by using of signal processing, modal parameter identification and finite element theory. In this study, dynamic characteristics testing, modal parameters identification and structure finite element establishing were comprehensive and systematic discussed. The main research results and innovation are as follows:Firstly, the dynamic characteristics of Chaobai River bridge was tested by car excitation. And the preprocessing program of the bridge vibration signal was compiled. The role of the software include: filtering, integration, smoothing, elimination of the trend term and certainty signal extraction from random vibration signal. This not only makes identification from mass of data faster, but also greatly improved the precision and accuracy of modal parameters identification.Secondly, two modal parameter identification methods: ZOOM-FFT method based on frequency domain and ARMA method based on time domain were discussed. The corresponding calculation procedure was also written, which provided an effective means for the analysis of structural dynamic characteristics, and could also serve as a means to test the correctness of theoretical model of finite element methods.Thirdly, the spatial finite element theoretic model of the Chaobai River bridge is constructed and modified according to the results of vibration test. The dynamic characteristics of this bridge was studied based on this model in order to master the changing rules of the bridge's natural frequencies and mode shape. After testing, the results were exact and credible, which provide theoretical basic for further research on bridge dynamic harmonic analysis.