Damage Identification Of Frame Structure Based On The Wavelet-artificial Immune Algorithm

Frame is a kind of structure which is widely used in engineering structure. The damage may occur due to the impact of natural or man-made factors,pose a threat to the safety of the structure. When these damages accumulate to some extent, it may lead to significant engineering accident. Therefore, research on the theory and method of damage identification of frame has great significance.Wavelet analysis is a new kind of signal processing method. The wavelet analysis can show the local characteristics of signal effectively in time and frequency domain and analyze the signal singularity position accurately. So the wavelet theory has been applied to the structural damage diagnosis. Artificial immune algorithm is a learning and optimizing artificial intelligence algorithm which is established by modelling the operation mechanism of biological immune system. Artificial immune algorithm has excellent global search ability which can be used to identify the structure damage degree. So, this paper is put forward the concept of wavelet-artificial immune algorithm based on the respective advantages of wavelet analysis and artificial immune algorithm and setting up a method of wavelet-artificial immune algorithm which can both identify frame structural damage location and degree.Taking the damage framework structure as the research object. The wavelet-artificial immune algorithm which was put forward in this paper was used to establish the element model of frame structure. Modal of structure can be analyzed by using Lanczos method, so the modal parameter of the damage frame structure can be calculated. The theory of wavelet analysis was applied to analyze the modal parameters of the structure to get the wavelet coefficient chart, The damage position of the frame structure can be identified by the singular point in the graphic. Then, the objective function which was established by the frequency and modal shape was regard as the antigen, and the degree of the damage elements which was identified by wavelet theory was regard as the antibody. The artificial immune algorithm was used for iterative calculation of global optimization, so the damage degree of the structurecan be identified.In this paper, finite element model of the damage frame structures with a layer of a cross(with two injuries or three injuries) and a layer of two cross(with three injuries or four injuries) is established. Set a variety of damage conditions for numerical simulation analysis. The damage position of the frame structure can be identified by the theory of wavelet analysis. The artificial immune algorithm can be used to identify the extent of structural damage on the basis of the damage location and quantity.The above method is applied to more complex damage frame structures with two layers of a cross(with three injuries or four injuries) and two layers of two cross(with two injuries or three injuries) on the basis of simple frame structure in this paper. The method is proved to be effective. This method can be used for reference in the engineering application of structural damage diagnosis.