13th International Conference on Fracture June 16–21, 2013, Beijing, China -8- Table 1 Results of damage identification Actual injury Low strain method/error New method/error damage location 7.4m 6.71m/9.3% 7.08m/4.3% damage severity 9.6% Small damage 10.2%/6.2% 4 Conclusion This paper selected efficient modal for damage identification applying the change rate of eigenvalues firstly, then established the small injury accurate recognition method based on the application of sensitivity of element modal strain energy to small structural injury and efficient local analysis capabilities of wavelet analysis. The efficiency and accuracy of the proposed method is verified by small cracks damage identification of the pile of Ouhai Sports Center. The concrete conclusions are as follows: (1) Fracture identification method proposed in this paper for the pile foundation can effectively identify the fracture damage location of the hidden structures in service, this method has a high recognition accuracy. (2) Fracture identification method proposed in this paper for the pile foundation can effectively identify the fracture damage severity of the hidden structures in service; it is able to quantify the degree of damage; it provides an important reference for the pile foundation fracture injury assessment. (3) The method presented in this paper provides a new approach to concealed structure damage identification. Acknowledgements This work was financially supported by Zhejiang Provincial Education Department’s research projects, the project name: Synchronous Identification Method of Structural damage and load under ambient excitation, project number: Y201223039. References [1]H.W. Zhou, W.T. Weng, Y. Wang. Several methods of the bridge pile testing. Highway and Transportation Research (Applied Technology Edition), 4(2012) 222-225. [2]X.L. Han, Y.X. Han, X.M. Tang. Numerical analysis of wave propagation in platform-pile system. Chinese journal of geotechnical engineering 6(2001) 105-107. [3]H.Y. Chai, M.G. Liu, S.W. Bai. Numerical analysis of wave propagation in platform-pile system. Chinese journal of geotechnical engineering, 5(2003) 624-628. [4]C.H. Zhang, J.L. Zhang, J.H. Xie, et al.. The multi-reflected wave analysis on the low strain integrity testing of pile foundation. Journal of xiamen university ：natural science, 3(2005)214-216. [5]Y.M. Chen. Got Method Drills in Pile Foundation Inspection About the Application Analysis. Construction and Design for Project, 7(2011)129-131. [6]C.X. Xiao. Application of ultrasonic transmission method to detecting integrity of large- diameter bored cast-in-place piles[J]. Rock and Soil Mechanics, S1(2003)169-171. [7]F.C. Liu，W. Wang，Z.S. Zhang，W.Q. Liu. Wave Analysis of Pile Foundation Low Strain Detection and Determination of Pile Body Integrity. Port Engineering Technology, 2(2012)46-48. [8]H.Q. Wu, R.Y. Ma，L.Y. Huang，J. Peng，L. Chen. General application and analysis of several detection methods in the engineering foundation piles. Concrete, 4(2012)119-121.
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