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Publication Number: FHWA-HRT-11-010
Date: January/February 2011
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The Federal Highway Administration's (FHWA) Long–Term Bridge Performance (LTBP) program is leading the way toward a better future for bridge performance. Launched in 2008 and now in its pilot project phase, the LTBP program will collect, maintain, and study high–quality, quantitative performance data for a representative sample of bridges nationwide. These bridges will feature many structural types and materials, as well as variations in geometry, age, traffic volume, truck loads, and climatic conditions. "This innovative program will lead the way towards identifying high–value, state–of–the–art procedures and practices for assuring bridge performance from cradle to grave," said Firas I. Sheikh Ibrahim, Team Leader for Infrastructure Management in FHWA's Office of Infrastructure Research and Development.
"The data collected by the program will support a better understanding of how and why bridges deteriorate, how to best prevent or mitigate deterioration, and how to most effectively focus development of the next generation of bridge management tools," said Hamid Ghasemi, Manager of the LTBP program at FHWA.
The first phase of the LTBP program included identifying the relevant data types to be collected; establishing a data management and analysis architecture; and developing protocols for data sampling, collection, and quality assurance. Pilot studies are now being conducted at seven bridges across the country to validate the methods and protocols developed during the first phase of the program and to investigate various details about the program management, so that high quality data collection can be ensured while minimizing disruptions to bridge owners and users. These details include the time, effort, and cost of preparation, field work, and collection and analysis of data; the cost of instrumentation and data collection systems; and the cost of traffic maintenance. During the pilot phase, researchers are also looking at the time needed to coordinate with bridge owners and obtain the necessary permits for work.
A ground–level view of a bridge in Sandstone, MN,
that carries State Road 123 over the Kettle River.
Located in California, Florida, Minnesota, New Jersey, New York, Utah, and Virginia, the pilot bridges represent both a broad geographic distribution and a cross section of the bridges that will be the focus of the LTBP program. The program will concentrate on the types of bridges heavily represented in the U.S. bridge population, including highway and interchange overpasses and bridges over minor waterways. Primary selection criteria for the pilot bridges were superstructure type, age, type of deck, composite versus noncomposite design, deck condition, environmental factors, annual average daily traffic (AADT), and the percentage of trucks in the traffic stream.
Selected pilot bridges include one that carries Southbound U.S. Route 15 over Interstate 66 in Prince William County, Virginia. Constructed in 1979, this two–span steel haunched girder bridge has a cast–in–place concrete deck and carries an AADT of 16,500 vehicles, with six percent trucks. Both the steel superstructure and the concrete deck are showing a significant degree of deterioration. The Minnesota pilot bridge, meanwhile, carries State Road 123 over the Kettle River in the town of Sandstone. Constructed in 1948, the steel deck truss bridge carries an AADT of 2,050, with eight percent trucks. And in New Jersey, the pilot bridge carries Eastbound Interstate 95 over Sharon Station Road near Allentown, New Jersey. This single span multi–beam steel girder bridge with a cast–in–place concrete deck was constructed in 1969 using stay–in–place forms. The bridge carries an AADT of 25,000 vehicles.
In the background is a bridge that carries Southbound U.S. Route 15
over Interstate 66 in Prince William County, VA.
The under side of a bridge on Eastbound Interstate 95 over
Sharon Station Road near Allentown, NJ.
The final pilot bridge to be studied carries Westbound State Road 430 over the Halifax River in Daytona, Florida. Built in 1997, the precast segmental box girder structure has multiple spans.
A ground–level side view of a bridge on Westbound State Road 430
over the Halifax River in Daytona, FL.
Researchers have conducted a detailed visual inspection of each bridge and analyzed the bridges using finite element modeling. Live load testing or dynamic testing were also performed to obtain baseline data on the structural behavior of the bridges. The deck of each bridge was inspected using several nondestructive testing methods, and cores were taken to help characterize the material qualities of the deck and the type and extent of any deterioration.
The data collected from the pilot bridges are now being evaluated to determine if any adjustments in the LTBP program protocols are needed. The pilot phase will be completed by the fall of 2011, with the regular long–term data collection phase of the program beginning this summer.
"The ultimate goal of the pilot study phase is to make certain that all of the components needed to achieve the long–term objectives of the LTBP program are specified before starting the nationwide study on a larger sample of the bridge population," said Ghasemi.
For more information on the LTBP program, visit http://www.fhwa.dot.gov/research/topics/infrastructure/bridges/subindex1.cfm (select "Long Term Bridge Performance"), or contact Hamid Ghasemi at FHWA, 202–493–3024 (email: email@example.com).
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