Engineers at Infrasense (Arlington, MA, USA) have recently completed subsurface investigations of seventeen bridge decks in the Greater Chicago area using infra-red thermography.
The information collected will facilitate planning efforts associated with the $3.4bn Elgin O'Hare Western Access Project, specifically with regards to the widening of the existing expressway.
Infra-red surveys reveal bridge deck delaminations because the delaminations interrupt the flow of heat through the deck. Delaminations occur when the concrete above and below the reinforcing steel begins to deteriorate due to increased stress caused by corrosion of the steel.
Traditional methods for the detection of delaminations in bridge decks -- such as chain dragging and hammer sounding -- take time to perform and require the complete closure of the lane being surveyed.
Despite the location of the decks on the Elgin O'Hare Expressway, which carries a high volume of traffic to and from metro Chicago, the infra-red surveys were performed without causing any traffic disruptions or backups.
During the survey, an Infrasense engineer reviewed the infra-red video data in real-time so that selected areas that appear delaminated in the infra-red image (higher in temperature than surrounding areas) could be hammer sounded to confirm the presence of delamination.
A map of each bridge was produced indicating the locations and areas of delaminations, as well as the areas where sounding was performed for confirmation.
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-- Dave Wilson, Senior Editor, Vision Systems Design