ARLINGTON, Mass. – The Northeast Bridge Preservation Partnership (NEBPP) recently hosted its annual meeting in Newport, Rhode Island. Hundreds of engineers from the state and private consulting firms and suppliers attended the conference to share new technologies and materials relevant to bridge maintenance, and discuss and improve current best practices for New York bridge preservation and rehabilitation. Infrasense engineers participated in the conference, showcasing our high speed bridge deck scanning capacities.
The meeting examined different state’s repair and maintenance practices for key bridge elements, including bridge decks. The importance of accurate and comprehensive condition information was stressed, as it is needed to help DOT personnel make effective preservation, rehabilitation, and replacement decisions. Over the years, a lack of reliable condition information, in some states, has lead to the replacement of decks in good condition and neglect of decks in poor condition. With large bridge inventories and the presence of asphalt overlays, many northeast highway agencies have primarily relied on visual inspection at the network level because chain dragging is too time-consuming to carry out on each bridge and ineffective on bridges with HMA overlays. Since deterioration largely occurs below the surface, it is not realized in visual inspections until there is a significant problem. Without network level subsurface information there is often misguided project-level focus.
Northeast highway agencies have utilized Ground Penetrating Radar (GPR) for bridge deck condition information. GPR data is collected to estimate rebar depth and identify corrosion. The GPR data is collected at highway speeds and requires no lane closures. Decks in good condition consist of strong and uniform radar reflections from the rebar. GPR data with weak and inconsistent reflections indicate rebar-level bridge deck deterioration. This technology is able to estimate the overall quantity of deteriorated concrete for a particular deck structure, as well as provide a plan area map showing the location of the deteriorated areas.
Infrasense has performed project-level and network-level GPR bridge deck surveys. The results yield a quantity of deteriorated area that is used for accurate and cost-efficient rehabilitation planning. For network-level surveys, Infrasense maximizes its efficiency by surveying a large number of decks with its multi-phase approach (up to 30 decks per day). After completing a quick and simple preliminary (Level 1) bridge deck analysis, many may be found to be in good condition and require no further analysis. Those found to have more significant deterioration levels are mapped in detail (Level 2), providing data to accurately plan, program, and budget maintenance and rehabilitation.
Recently, an independent consultant hired by the Minnesota Department of Transportation performed a study evaluating the accuracy of the Infrasense’s results for 12 bridge decks surveyed in Minnesota. For each bridge deck, the study compared the deterioration quantities predicted by Infrasense against subsequent construction repair quantities. The study found that, on average, Infrasense’s predicted deterioration quantities were within 4% of the documented construction quantities.