Research On Wavelet Analysis And Damage Diagnosis Of Dynamic Response Data Of Cable-stayed Bridges

Wavelet analysis has the advantages of multi-resolution analysis,and has the ability to characterize signal characteristics in both time and frequency domains.This ability is particularly important for damage diagnosis of cable-stayed bridges.The dynamic response signal test is convenient,simple and fast,and is widely used in the field of health monitoring.In order to further explore the application of wavelet analysis method in the field of cable-stayed bridge damage diagnosis,the wavelet analysis and damage diagnosis of cable-stayed bridge dynamic response data are studied.The main research work is as follows :(1)The theories of short-time Fourier transform,continuous wavelet transform,discrete wavelet transform,multi-resolution analysis and wavelet packet analysis are summarized.The short-time Fourier transform,continuous wavelet transform,discrete wavelet transform,multi-resolution analysis and wavelet packet analysis are realized by MATLAB programming.(2)Based on the theory of discrete wavelet transform,the damage identification index of wavelet total energy difference is derived,which is obtained by the difference of wavelet energy.Through the example of cable-stayed bridge,the benchmark finite element model of cable-stayed bridge is established,and the optimal wavelet basis and layers are determined.The damage index of wavelet total energy difference is used to locate the damage of main girder of cable-stayed bridge.(3)The damage identification method of cable-stayed bridge based on the variation coefficient of wavelet packet energy transfer rate is proposed.Based on the wavelet packet energy transfer rate,the wavelet packet energy transfer rate and the variation coefficient are fused to derive the damage index QD(Quantization Different)and the damage degree index DL(Damage Level)of the variation coefficient of wavelet packet energy transfer rate.The effectiveness of the proposed method is verified by the example analysis of cable-stayed bridge.The damage condition of the main girder is set and the transient dynamic analysis of the benchmark finite element model of the cable-stayed bridge under environmental excitation is carried out to determine the optimal wavelet packet basis and number of layers.The dynamic response of the real bridge is decomposed and reconstructed by wavelet packet.The obtained data are used as input to obtain the damage index and damage degree index of the real bridge,and then the damage of the real bridge is judged.(4)A damage identification method based on the sum of curvature of wavelet packet energy change rate is proposed.Based on the wavelet packet energy analysis method,the expression of wavelet packet energy change rate is derived,and then the curvature of wavelet packet energy change rate is obtained by second-order difference method.The curvature of wavelet packet energy change rate at the end point is derived by Taylor formula,and the damage index of the sum of curvature of wavelet packet energy change rate is derived by summation formula.The proposed method is verified by the simulation analysis of cable-stayed bridge,and the noise robustness analysis is carried out.The measured response of the real bridge is extracted,and the wavelet packet decomposition and reconstruction are carried out.The proposed method is used to identify the damage of the real bridge.