Easy Up, Not-So-Easy Down
Builders replace bridge in only days using lightweight, corrosion-resistant composites
Using new fiberglass-polymer materials, contractors in Springfield, Mo., have just subjected a decaying, 70-year-old bridge to a makeover that was as quick as it was dramatic.
Instead of snarling traffic for two to three weeks while they repaired the crumbling deck, girders and guardrails by conventional methods--laying plywood, tying steel rebar and pouring concrete--the workers used pre-fabricated plates and cages developed by a National Science Foundation (NSF)-supported university-industry partnership to finish the job in a mere five days.
The NSF's Repair of Buildings and Bridges with Composites Industry-University Cooperative Research Center is based at the University of Missouri at Rolla and North Carolina State University. The Missouri researchers joined with their industry partners and colleagues at the University of Wisconsin at Madison to develop the new construction solution.
The target of the makeover, an old bridge on Farm Road 148 near Springfield, was one of as many as 156,000 U.S. bridges in need of repair. In fact, it was posted, meaning that local officials had imposed a vehicle weight limit due to the dangerous bridge conditions. Now, however, a fresh layer of concrete conceals the technology responsible for the rapid replacement of the bridge’s crumbling deck and guardrails.
"A key to tackling the challenge of making thousands of deficient bridges in the nation fully operational and safe again is the development of convenient solutions for the rapid construction of long-lasting bridges," says Fabio Matta, a Ph.D. candidate in structural engineering who helped develop the new construction system. "Advanced composites make the margin for improvements exceptional," he added.
The fiberglass-polymer composites are strong enough to endure several decades of traffic--and unlike steel, will resist the ravages of salt and other corrosive de-icers for just as long. Due to the lightweight and prefabricated nature of the materials, moreover, workers can put the structures in place quickly, saving both time and commuter headaches.
"Since its inception in 1998, we have worked with our NSF I/UCRC partners to provide solutions for our ageing infrastructure," says Antonio Nanni, director of the Missouri center.
"We have demonstrated the economical and technical feasibility of several very attractive technologies," Nanni added. "Their full deployment will become possible only with the modification of existing codes and standards. It is a long process, but we are seeing light at the end of the tunnel."The bridge, renovated with a grant from the U.S. Department of Transportation, was rededicated on Feb. 22, 2006.
The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2017, its budget is $7.5 billion. NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and other institutions. Each year, NSF receives more than 48,000 competitive proposals for funding and makes about 12,000 new funding awards.
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