Study On Beam Damage Detection Based On Wavelet Analysis

Damage in the civil engineering structure has brought a lot of hidden danger. Find and repair damage as soon as possible has very important significance to reducing the possibility of accident. How can we find structural damages that exist in the internal structure, which requires the development of damage identification technology that can be used in practical.Damage identification was first applied in the field of mechanical, structural nondestructive testing technology was developed in the1960s. In this period, the researchers proposed a lot of damage identification methods according to different structure on the different conditions. Wavelet analysis gets the favors of many scholars because it not only can describe the signal’s local features but also can describe signal’s overall features. The damage location and degree of concrete beam is studied in the paper by using wavelet theory. The main contents are as follows:First of all, this paper introduced the current situation of the development of damage identification at home and abroad and also introduced the basic theory and nature of wavelet analysis. The paper also reviewed the development process of wavelet theory and the basic transform method, including continuous wavelet transform、discrete wavelet transform analysis and multiple scale analysis. After that the paper mainly introduced the basic principle of wavelet analysis and its application in the damage detection.Secondly, three kinds of damage beam is simulated by finite element analysis software. Using the bior6.8wavelet to the curve of mode shapes, the damage location can be identified by analyzing the multi-scale wavelet transform coefficients and the coefficients difference between perfect and damage beam. The advantages and disadvantages of the two identification parameters above mentioned are analyzed. The result shows the peaks of wavelet transform coefficients can indicate the damage location. But it is difficult to detect the location of defect if it is near to the equilibrium position of vibration. In order to solve this problem, the method which is to add the wavelet transform coefficients of multi modals together is put forward in this paper. The damage degree of simply support beam is discussed by using Lipschitz exponent in the paper.Finally, two models of simply support beams with different damage condition are made. The first order of beam formation is obtained by INV testing system. The damage locations are clearly indicated by the modulus maxima of the wavelet transform coefficients. The results verified the feasibility of the method.