Dynamic Monitoring of Fatigue Crack Process of Orthotropic Steel Bridge Structure with Acoustic Emission Yuling Zhang1，Qiao Rong1，Delian Kong2，Wenyou Wang2 Fengjing Xu2，Weiping Dong2,* 1Railway Engineering Research Institute, CARS, Beijing 100081, China 2Physical Acoustics Beijing, Beijing 100029, China *Corresponding author: Jason.dong@mistrasgroup.com __________________________________________________________________________________ Abstract This paper introduces how to use acoustic emission (AE) technology to monitor dynamic process of crack growth of a segment model of a full size orthotropic steel bridge structure during a 30 day fatigue test. The dimension of the test model is 12.54x2.99x0.6 (LxWxH) meter. Multiple AE sensors were located on different places of the structure. Crack initiation, location and development process were dynamically monitored and recorded. This paper discusses how AE technology is used in the fatigue test of large structure, how is burst crack signal captured, how is crack location identified, what are the behavior of crack developments and how is the result of visual inspection in comparison with the AE technology. The results of the fatigue test monitored with AE have shown that AE is a very valuable technology for monitoring dynamic process of crack development. It can be used not only for various tension, compression and fatigue tests in labs, but also for structure health monitoring in the fields. Keywords Fatigue Crack, Fracture, Damage, Acoustic Emission, Dynamic Monitoring _________________________________________________________________________________________________________________________________ 1. Introduction Although orthotropic steel bridge structure is getting more and more widely used, fatigue cracks on the welds and the structure material are still concerns due to the complexity the orthotropic structure and stress concentration in the welds under repeated loadings of the structure[1-2]. It is not uncommon that cracks were found in an orthotropic steel structure that is younger than its design or predicated life age. The actual fracture behavior of orthotropic steel structure were not fully studied and experimentally tested yet. In fatigue tests of structures or materials, strain or stress measurement is usually a very common way for fatigue crack detection. But, not only the strain measurement cannot tell the development process of the crack growth, but also for a big or complex structure, e.g. a full size orthotropic steel deck, it is hard to predict where the cracks are going to occur and where are the optimum positions that strain gauges should be installed. Each strain gauge can only measure the stress where the strain gauge sticks to and its vicinity, it is not possible to show
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