ICF13B

5. Conclusions This paper has applied acoustic emission technology for monitoring the dynamic process of fatigue crack initiation and growing of a full size orthotropic steel bridge deck. Experimental results have proven: 1). AE is an effective technology for structure health monitoring, specially AE can monitor the whole dynamic development process from crack initiation and growth to structure fracture. Not only AE can tell when a crack is initiated, but also it can tell where the crack is located and how it develops. 2). AE has much higher sensitivity for active crack identification than any other NDT technologies. It can detect microscopic crack activity and is able to report crack initiation in hours or days in advance of visual inspection and other technologies. This actually draws another inference, i.e. a fatigue test may not be able to find correct material life cycle without using AE for crack detection. 3). In the experiment, it was found that the cracks of the tested deck are not necessarily found in welds, but also it existed in other weak locations of the structure material. Acknowledgement The authors would like to thank Ed Zhou from URS Corporation in US for his help and suggestive discussions in implementing this project. References [1] S.T. de Freitas, H. Kolstein, F. Bijlaard, Structural monitoring of a strengthened orthotropic steel bridge deck using strain data, Structural Health Monitoring, Vol. 11, No. 5, September 2012, 558 – 576. [2] C. Wang, L. Tian, B. Fu, Fatigue cracking monitoring and evaluation using smart sensors for steel bridge decks, Bridge Maintenance, Safety Management, Resilience and Sustainability, Biondini & Frangopol (Eds), 2012 Taylor & Francis Group, London, ISBN 978-0-415-62124-3. [3] Inspecting Bridges with Acoustic Emission, Technical Report TR-103-12, Physical Acoustics Corporation, 1996. [4] J. A. Mckeefry and C. K. Shield, Acoustic Monitoring of Fatigue Cracks in Steel Bridge Girders, Minnesota DOT Report MN/RC-1999-36, September, 1999. [5] A. Schultz, Development of An Advanced Structural Monitoring System, Minnesota DOT Report MN/RC 2010-39, November, 2010. [6] M.B. Johnson, D. Ozevin, G.A. Washer, K. Ono, R.S. Gostautas, T.A. Tamutus, Real time steel fatigue crack detection in eyebar using acoustic emission method. Journal of the Transportation Research Board, accepted in 2012. [7] T.M. Roberts, M. Talebzadeh, Acoustic emission monitoring of fatigue crack propagation, Journal of Constructional Steel Research 59 (2003) 695 – 712.

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