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|NDT.net Issue - 2012-04 - NEWS |
Infrasense has recently performed nondestructive evaluations of 12 bridge decks in the Greater Chicago area using Infrared Thermography to accurately report delaminated areas. Despite deck locations in areas of high traffic volume, the decks were evaluated in just two days without any disruption to normal traffic flow.
Arlington, MA (PRWEB) March 21, 2012. Infrasense, Inc., a national leader in detecting subsurface conditions, recently completed subsurface investigations for 12 bridge decks in the Greater Chicago area using Infrared Thermography (IR). These tests yielded a detailed condition evaluation of each deck, including maps of delaminated areas, without requiring cores or extensive closures, and with minimal disruption to traffic flow. The infrared data was supplemented with Impact Echo (IE) tests to confirm locations of delamination.
The field work was carried out by Infrasense on the 12 decks just two days. Despite the location of these decks on major state and Interstate highways with high traffic volume in metro Chicago, the surveys were performed without causing any traffic disruptions or backups. Each lane of the each deck was surveyed once using a rolling closure. During the infrared surveys, impact echo testing was performed to confirm selected areas of delamination and calibrate the infrared images during the off-site data analysis.
Infrared surveys reveal bridge deck delaminations since 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. These delaminations are essentially thin voids in the concrete at the reinforcing steel level, which change the thermal profile of the deck; delaminated areas appear as hot spots in the infrared survey, which are detectable by a sensitive infrared camera. 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. Due to the subjective nature of these traditional methods, the results can be less reliable in noisy environments with heavy traffic flow.
Infrared data is collected in a series of passes across each deck, with each pass covering a deck width of between 12 and 15 feet. For a typical interstate deck with 2 lanes and left and right shoulders, the survey is carried out in four passes one in each lane and one in each shoulder. During the survey, an Infrasense engineer reviews the infrared video data in real-time, and selected areas that appear delaminated in the IR image (higher in temperature than surrounding areas) are manually sounded to confirm the presence of delamination. The survey also produces a series of infrared images collected every foot of vehicle travel that are stored and processed off-site for detailed delamination mapping and quantification. Infrasense delivers a map of each surveyed bridge indicating locations and areas of delaminations, as well as areas where sounding and impact-echo ultrasonic testing were performed for confirmation.
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