New Impulse Radar Strategies for Bridge Deck Assessment
R. Reel, T. Tharmabala, Il. Wood,
T. Chung, and C. R. Carter
Appears on pages(s):
asphalts; bridge decks; field tests; nondestructive tests
Traditional methods of collecting data on the condition of bridges are expensive and time consuming, and the results are not always dependable. Since the early 1980’s, the Ministry of Transportation, Ontario (MT01 and the Communications Research Laboratory (CRL) at McMaster University have been involved in the use of impulse radar for the assessment of asphalt-covered bridge decks through a program called Deck Assessment by Radar Technology (DART). In this paper, a correlation study involving comparisons between the predictions of the DART survey and the actually observed conditions of the decks (after removal of asphalt during rehabilitation) is discussed with emphasis on the processing of the radar waveforms. Since a large volume of radar data is collected from bridge decks, it is important to develop strategies to extract the salient features from the reflected signal. These strategies include: first, a thresholding method and strata plot which are very effective in locating subsurface layers; and, second a differencing technique which has the capability of discriminating between sound concrete and damaged concrete. The comparisons demonstrate that there is a good correlation between the DART survey and the actual condition of bridge decks.