As one of the non-destructive testing (NDT) methods, acoustic emission (AE) can be widely applied to the field of engineering and applied science owing to its advantageous characteristics. In particular, the AE method is effectively applied to monitor concrete structures in civil engineering. For this technology to be employed in a monitoring system, it is necessary to investigate the propagation characteristics of the AE in structures. Hence, this study investigates the characteristics of AE in concrete structures to evaluate the field applicability of AE monitoring systems. To achieve this goal, experiments employing an AE system are conducted for concrete structures 20 × 0.2 × 1.2 m in length, width, and height, respectively, to explore the AE parameters according to the impact energy. Among all AE parameters, absolute energy is determined to be most sensitive factor with respect to the impact energy. In addition, the attenuation effect of the AE wave is quantitatively evaluated according to the wave propagation distance. Moreover, the concept of effective distance is newly suggested based on the experimental results. The effective distance is shown to increase as the impact energy increases, although the increased effective distance is limited because the damaged AE signal is of high frequency. This study helps improve the field applicability of AE monitoring systems by suggesting suitable AE sensor spacing, which contributes to promote the practice of technology.

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Health monitoring of structures is required when earthquakes occur in urban areas where buildings are highly concentrated, and in such situations, it is very important to estimate the location of structural damage. To improve the accuracy of damage location, proper wave velocities must be determined based on the characteristics of the propagation media. In this study, experiments were performed to measure the P-wave and surface wave velocities of a granite specimen. In addition, the elastic wave velocities of the specimen were measured based on the distance between the sensor and the source location, and these measurements were compared to the P-wave and surface wave velocities. The experimental results were analyzed to determine the accuracy of the source location. The findings of this study will be useful in the field for estimating the source location of structures damaged by earthquakes.

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