13th International Conference on Fracture June 16–21, 2013, Beijing, China -4- 3. Experimental setup and operation According to the aforementioned crack source localization problem in masonry structure, several tests based on a two-arch masonry model bridge are operated in this research. 3.1. Wave velocity test A series of pencil-lead break tests are performed on the central pier of the bridge to study the attenuation and the velocity properties. The size of the central pier is of 160×50×28 cm, shown in Fig. 2, and it can be considered as a representative masonry solid structure. Six sensors (S0~S5) are used to detect AE signals and the distance between two adjacent sensors increased from S1-0 to S5-4 with an increment of 5 units, shown in Fig. 2. The pencil is broken beneath the sensor S0 with 5cm distance away in the same surface to study the surface velocity propagation, which is the scenario shown in Fig. 2. Figure 2. Wave velocity test: (Left) the sketch of the pencil-lead break point and the sensor distribution; (Right) scenario of the velocity test. The results of the measured velocities are shown in Fig. 3. The velocity named V-homogeneous, is calculated assumed the material is homogeneous [6]. The V-average is the average velocity value of all the calculated velocities in the corresponding test. Figure 3. Wave velocity of the AE on the surface of masonry model bridge.
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