Measurement of surface wave transmission coefficient across surface-breaking cracks and notches in concrete

Abstract

In this paper, a technique for measuring a surface wave transmission coefficient across surface-breaking cracks and notches in a heterogeneous but globally isotropic material (concrete) is presented. Once the transmission coefficient across a surface discontinuity is known, its depth may be estimated. There are many difficulties in measuring the transmission coefficient experimentally owing to effects of wave path dependence, unknown characteristics of the receiver and the wave source, and the variation of impact event or receiver coupling. To eliminate the undesired effects, a self-calibrating measurement scheme is applied to obtain the surface wave transmission coefficient across notches and surface-breaking cracks in concrete. The obtained signal transmission coefficient is not affected by the experimental setup or the heterogeneous nature of the material. The testing scheme is described and experimental results obtained from concrete specimens with notches and surface-breaking cracks are presented. Repeatable and reliable measurements of surface wave transmission coefficient are obtained, which demonstrate a strong relation to normalized discontinuity depth. A numerical study using the boundary element method is presented, which verifies the experimental findings.

Nondestructive Evaluation of Crack Depth in Concrete Using PCA-compressed Wave Transmission Function and Neural Networks

“…Several studies on nondestructive techniques to characterize surface-opening crack depth in concrete have been reported [1][2][3][4][5][6][7][8][9]. Among them, mechanical wave (both body and surface waves) transmission methods demonstrate superior sensitivity to the presence of cracking along the wave path in concrete [5][6][7][8][9][10][11].…”

The Use of Surface Waves to Estimate In-Place Strength of Concrete

“…Five time domain signals, which result from five repeated impacts, are collected by each sensor and processed in the computer based on a common feature (the first significant valley) centered in the time window. Five transmission functions are computed and then averaged to obtain one (Song et al, 2003). Figure 1 shows typical time domain response signals.…”

Air-Coupled Surface Wave Transmission Measurement Across a Partially Closed Surface-Breaking Crack in Concrete

“…For concrete, a heterogeneous but globally isotropic material, Hevin et al [3] obtained the transmission ratio of surface wave in frequency domain using numerical simulations, and proposed the cut-off frequency (h/Ȝ =0.3) method to estimate crack depth. Popovics and Song et al [4][5] also obtained the Tr and h/Ȝ relationship through experiments and boundary element analysis. For surface wave transmission measurements, they used a self-calibrating procedure to eliminate surface coupling inconsistency and geometric attenuation effects.…”