The Research On The Moving Mass Method Of Damage Detection In Beam

This paper mainly studies a new method of structural damage identification—moving mass method. Firstly introduce in detail its implementing steps and theory analysis. Under the premise of needing the information of both beam's before and after damaging, this paper proposes a new method, which can detect roughly the damage location. The method only uses the first natural frequencies from the moving mass method. Numerical simulation results show its effectiveness.As the method can only detect single damage in beam, this paper proposes the method of combining moving mass method and neural network to detect structural damage. A BP neural network and radial basis neural network are designed by the MATLAB soft. The first natural frequencies from the moving mass method are used directly as the input vector of the neural network. The results show that after training with the sample from single damage condition the neural network can detect both single damage location and damage level of damaged structure;Compared with BP neural network, radial basis neural network need much less time to train, and after adjusting the value of 'spread' carefully, the generalization can be improved greatly, so it is recommended to use radial basis neural network for structural damage identification.Moving mass method is a practical structural damage identification method with much prospect. The current experimental modal analysis has developed various methods to measure the natural frequencies of structure. The natural frequencies of structure can be measured with very high accuracy. In the meantime, measuring structural displacement modes and strain modes needs a large number of sensors, and their measured accuracy is comparatively lower than the natural frequencies'. So although other methods, such as flexibility curvature, curvature mode, mode energy and so on, are more sensitive to damage, they need displacement modes or strain modes. Theoretically they can be workable, but practically they are difficult to apply. The moving mass method only measures the natural frequencies of structure, which makes it possible to detect structural damage conveniently and easily in practice.