Elastic Wave Velocity and Attenuation Tomography Using Randomly-Induced Excitations for Damage Detection of RC Slab

Abstract

As it is imperative for the damage evaluation of infrastructures to establish an efficient non-destructive testing (NDT), an acoustic emission (AE) tomography technique has been developed. Authors has been studying tomography techniques based on elastic-wave and acoustic emission (AE) to visualize the internal defects in concrete. In the result of AE tomography, it can reasonably be assumed that lower elastic-wave velocity corresponds to heavier deterioration. Thus, the AE tomography estimates wave velocity distribution, which is supposed to be decreased as the damage progresses, inside the reinforced concrete. The AE tomography combines an iterative AE source location algorithm with travel-time tomography to produce a 3D visualization of the elastic wave velocity. However, since the computation for the elastic wave ray-trace algorithm considering all potential detours of elastic waves takes up much time, and in the case that only a few AE signals are detected, AE tomography technique does not always work efficiently. In this paper, AE signals induced by random hammering and rain droplets, which provide elastic waves with a variety of frequency, on surface of RC deck are utilized as elastic waves’ excitations, and wave velocity and attenuation tomography assuming linear ray paths are performed in conjunction with AE source locations. Accordingly, random hammering lead to a hundred of AE events after in-situ measurement for a few minutes and rain-induced elastic waves also does to thousands of those as well for an hour. Consequently, the 3D tomography results show accurate and time-saving analysis, compared to the above-mentioned conventional AE tomography technique, for quantifying the damage of RC slab.