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Publication Number: FHWA-RD-99-107
Date: September 1999
How do you build a more durable bridge? This question continually confronts State highway agencies, who spend $5 billion a year to rehabilitate and replace deficient and deteriorating bridges. The biggest culprit is corrosion caused by deicing salts. One promising solution that the Federal Highway Administration (FHWA) and State highway agencies are now exploring involves using space-age, high-performance, nonmetallic materials, known as fiber-reinforced polymer (FRP) composites, in bridge construction. The composites are typically made of such fibers as glass, aramid, and carbon, as well as polymer resin matrixes. The composite materials are more corrosion resistant than conventional steel.
Prince George's County, Maryland, plans to build 11 or 12 new bridges within the next 3 years-a threefold increase over its typical construction schedule. If Edward Binseel, associate director of the Prince George's County Department of Public Works and Transportation, has his way, some of the bridges will be designed and built using high-performance concrete (HPC). All will be simple spans ranging from 7.3 to 18m (24 to 60 ft) feet in length, and all will be financed by the county, with no State or Federal funding.
With the recent launch of the long-term pavement performance (LTPP) program's Rigid Pavement Design Software, States have an important new tool to use in designing and building portland cement concrete pavements. The software is in the form of a Microsoft Excel spreadsheet. It allows engineers to tailor the pavement design to site-specific materials and traffic conditions, resulting in a more cost-effective and reliable design.
How do you help a drowsy or distracted driver avoid crashing? One strategy is to install rumble strips on the roadway shoulders. The strips, which are raised or grooved patterns in the pavement, create an audible rumbling sound and a vibration in the steering wheel when a vehicle drives over them. The sound and vibration can wake a sleeping driver-giving him or her time to regain control of the vehicle.
Motorists driving Route 23 through rural Delaware County, Ohio, north of Columbus, must wonder at an isolated 5 km (3-mi) stretch of road where the four-lane highway expands to eight lanes. Motorists are diverted onto the four lanes that occupy what used to be the median; the outside lanes are closed to through traffic. To pavement engineers, however, the lanes those motorists are traveling on represent an opportunity to learn how climate and cumulative traffic loading affect pavements of differing compositions and layering thickness. Constructed in 1995 by the Ohio Department of Transportation (DOT) and the Federal Highway Administration (FHWA), the southbound asphalt concrete (AC) and northbound portland cement concrete (PCC) lanes serve as a test site for the long-term pavement performance (LTPP) program.
States plan to build 3,211 Superpave pavements this year-double the 1998 number, according to a new survey by the Superpave Lead States team. This figure represents 41 percent of States' total hot-mix asphalt road projects this year. The third annual Lead States survey covered the State-level highway agencies in all 50 States, the District of Columbia, and Puerto Rico.
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