Study of acoustic waveguides for reinforced concrete structures

Abstract

To enhance the transmission of Acoustic Emission (AE) signals in high attenuation concrete material, an AE monitoring system composed of two-dimensional acoustic surface waveguides is developed. The design of the surface waveguide system and the AE source location results are presented. In this study, steel wires were selected as a waveguide material. The waveguides were attached on the surface of reinforced concrete structures. AE sensors were mounted at the ends of the waveguides. Since the waveguides were connected to the concrete slab at joints with limited contact areas, only small amount of AE energy could dissipate back to the concrete. Thus, AE signals can be transmitted a longer distance. Experiments using pencil-lead breaks were conducted on a concrete slab’s surface to provide artificial AE signals. High transmission efficiencies were experimentally determined for the epoxy joints developed to attach the waveguides on the concrete surface. Results confirm that the use of the surface waveguides can significantly increase the AE monitoring range. A multi-layer Neural Network (NN) system was employed to predict the locations of the AE sources. Four data sets of AE parameters and their corresponding source locations were used to train the NN system. A test data set was then used to demonstrate the effectiveness of the NN’s source-location predictions. Satisfactory results in predicting the AE source locations using the NN system were obtained.