Void-underneath Identification Method of Cement Concrete Pavement Using Vibration Transmissibility Function

To improve the measurement accuracy and efficiency of void-underneath identification of concrete pavement, an slab void-underneath identification method based on transmissibility function was proposed. First, a nine-slab 3-D finite element model of concrete pavement was developed, and the acceleration responses induced by an impact load were then collected for transmissibility function. Second, in two vibration transmission directions, the transmissibility functions between adjacent pairs of measuring points were calculated seperately. The differences in the tansmissibility functions within specific frequency bands were analyzed, and transmissibility-damage indicator (TDI) matrices and their matrix expression were proposed. Finally, 11 scenarios, including different types and degrees of void-underneath, were analyzed. Moreover, the effects of measurement points' distribution and noise levels on identification performances were studied. Results show that the two TDI matrices are suitable for the identifications of corner-void-underneath and edge-void-underneath. Both two TDI matrices are sensitive to corner-void-underneath, while only one TDI matrix whose transmitting direction is perpendicular to the corresponding edge is sensitive to edge-void-underneath. The effects of center-void-underneath on the two TDI matrices are not significant, as the distribution of void-underneath is not consistent with the distribution of TDIs. For the multi-area void-underneath, the trends of the two TDI matrices are similar to the single-point void-underneath. The distribution of measurement points affects the identification performance significantly. Denser measurement points would provide more accurate identification results. In addition, this identification method is very sensitive to the noise, high noise level results in poor identification performance. It is recommended to use this method under low noise level.