Automated Acoustic Scanning of Concrete Bridge Decks

Abstract

Chain drag testing is commonly used in current practice for bridge deck evaluation due to its low cost and ease of use. However, this method is subjective, and highly depends on the experience of the operators. An automated acoustic scanning system is developed to detect delaminations in concrete bridge decks. The system consists of an array of chains or impactors, a noncontact MEMS microphone sensor array, multichannel data acquisition device, RTK GPS positioning system, and signal processing schemes. Acoustic signal collected by the microphone is processed by short time Fourier transform (STFT). STFT amplitudes in the frequency range from 0.5 kHz to 5 kHz is summed up to form one dimensional data set vs. scanning time for each channel, and then data sets for each channel are stacked together to generate a two-dimensional map. A delamination identification algorithm is then developed to identify the center positons, dimensions of delaminations and recognize false positive delaminations. This system is validated on a 300 feet long bridge near Lincoln NE.