The Application Of Wavelet Analysis In Damage Identification Of Frame Structure

Frequent occurrences of natural corrosion and different disaster inevitably cause variable damage in structures which is in complicated service environment. Structural damage identification, correct evaluation and repair play an important role in greatly reducing the loss of lives and properties. Wavelet Analysis is recently getting utilized in many fields due to its ability to deal with the signal both in time and frequency domains, especially for the merit that it can deal with the non-stationary signals perfectly. Structural damage identification using Wavelet Analysis is an active research domain in current structure engineering and has strong engineering background. The correlative theory and technology are developing continuously.In this thesis the theory of structural damage identification based on wavelet analysis are studied carefully. The main efforts are devoted to the following aspects:1. The basic theory of wavelet transform,wavelet packet transform and Hilbert-Huang Transform is introduced simply. And the method and steps of using wavelet analysis,wavelet packet analysis and Hilbert-Huang Transform for structure damage identification is explained here.2. According to the method of Wilson_θ, the frame structural analysis program of a three-freedom-model is designed, which makes use of MATLAB language. The damage is simulated by reducing stiffness of damage part. The gotten acceleration response signal of each layer is transformed by wavelet, wavelet packet and HHT. The application of wavelet transform,wavelet packet transform and Hilbert-Huang Transform in three-freedom-model structural damage identification is achieved.3. Frame structure dynamical response analysis is done using ANSYS finite element analysis software. The damage is simulated by reducing modulus of elasticity of damage part. The gotten acceleration response signal of each measuring point is transformed by wavelet, wavelet packet and HHT. The application of wavelet transform,wavelet packet transform and Hilbert-Huang Transform in frame structural damage identification is achieved as such.The result of study show that Time-Frequency analysis method that is used to detect the structural damage online is excellent, the method conquer the defect of traditional method that can not time the damage and local the site of damage in structure simultaneously, namely the method can detect and identify structural damage promptly while it happens, consequently structural damage is detected and identified early, and the authentic foundation is provided for the service and reinforcement of structure.