CHARLOTTESVILLE – As part of the rehabilitation of the historic Hawthorne Street Bridge in Covington in Alleghany County, the Virginia Department of Transportation (VDOT) will install an innovative and lighter-weight deck on this structure. The 75-foot-long steel-truss bridge over the current CSX rail line was built in the late 1800s and is eligible for inclusion on the National Register of Historic Places.
Placement of a new fiber-reinforced polymer
bridge deck will begin the week of August 29, 2006. Corrosion and other infrastructure damage had rendered the bridge unsafe for vehicle and pedestrian traffic. After VDOT completes this project for the City of
Covington , the bridge is scheduled to reopen to traffic in the fall.
Fiber-reinforced polymers combine resin, additives and fillers with a reinforcing agent such as glass or carbon. The marine and aerospace industries have used fiber-reinforced polymer (FRP) materials for several decades. While its initial fabrication costs are higher than that of steel, the benefits of FRP’s longer life and lower maintenance costs outweigh the initial expense.
Before it closed, the old bridge had a 7-ton load rating; VDOT researchers expect that the new maximum permissible load will be 20 tons. Reopening the Hawthorne Street Bridge in the center of town also means emergency vehicles no longer will have to rely on rail underpasses elsewhere in Covington that are prone to flooding. Because of issues with intersections on either side of the bridge (road grade, alignment, right of way), VDOT could not build a new bridge that would meet current federal standards, thus its decision, at the request of the city, to rehabilitate the current bridge within its existing physical restraints.
The Virginia Transportation Research Council, VDOT’s research division, received $346,239 in 2004 from the Federal Highway Administration’s Innovative Bridge Research & Construction program to fund research and materials for this part of the bridge rehabilitation. Specifically, $55,000 of that was used to offset additional cost of the material; the Virginia Cooperative Center for Bridge Engineering at Virginia Tech used the balance to evaluate how this material would perform on this particular bridge.
Park Thompson, bridge engineer in VDOT’s Staunton District, who is overseeing the rehabilitation of the Hawthorne Street Bridge, said, “This is a great opportunity to use new technology to save this historic structure.”
FRP is gaining acceptance throughout the United States and around the world as a light-weight alternative to traditional steel and reinforced concrete bridge decks. While other states also are testing and installing FRP decks in new bridges and in rehabilitated historic structures, this is the first bridge in Virginia to use an FRP deck for vehicular traffic.
As part of Virginia Tech’s research into FRP bridge decks, individual FRP deck panels were placed in a test bed at the Troutville weigh station on Interstate 81, where they withstood the millions of heavy trucks along that busy corridor. The Virginia Transportation Research Council (VTRC) is also overseeing the installation of FRP decks on two new bridges on Tangier Island in the Chesapeake Bay that will replace two old wooden bridges. VTRC received $400,000 through the same FHWA innovative bridge research program this year for VDOT’s Tangier Island bridge work.