Infrasense recently completed high-speed infrared thermography scanning of 11 bridge decks for the Michigan DOT. The infrared data was collected with corresponding high resolution video at driving speed using a vehicle-based system. With this, no lane closures were required, and most importantly, traffic was unaffected. The infrared and video data collected for each of the 11 decks was analyzed to quantify and map overlay debonding, rebar-level delamination, patching, and spalling. Michigan DOT plans to use the deck condition information for prioritizing and planning rehabilitation projects.
Infrared scanning is being used by an increasing number of transportation agencies to efficiently obtain quantitative and comprehensive deck condition information. The ability to evaluate the condition of a large number of decks in a single inspection season is a valuable bridge management tool. Quantities and maps resulting from infrared scanning surveys allow for robust, data-driven decisions, and help to optimize the use of shrinking budgets.
Over the past 5 years Infrasense has completed infrared surveys of over 700 bridge decks in States such as Wisconsin, Minnesota, Idaho, Illinois, Wyoming, and Nevada. A majority of these decks carry major interstates, and range in size from a single span to a 1.5 mile-long viaduct.
Infrasense carries out infrared surveys according to ASTM D 4788 – 03 using a vehicle-based system that covers one lane per driving pass. For a typical 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. Each pass covers a deck width of 12 to 15 feet. The survey produces a series of infrared and visual images across the length of the deck. During the analysis, infrared data is reviewed simultaneously with the video data to differentiate delaminated areas from surface features (discoloration, oil stains, sand and rust deposits, etc.) that appear in the infrared, but are unrelated to subsurface conditions. Distinct areas with relatively higher temperatures that are unrelated to surface conditions are quantified and mapped. These are "hot spots" where the surface temperatures are higher due to the thermal barrier produced by the delaminations. The resulting delamination maps, which also include patching and spalling, are provided in CADD compatible format.