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A new composite application from a group of researchers at the National Science Foundation (NSF) could have a significant impact on old or worn out bridges around the world.
(Published on October-November 2006 – JEC Magazine #28)
A 70-year-old bridge in Springfield, Missouri has received a fibreglass makeover that has effectively turned back the clock on the battered edifice and made it safer and more durable than ever. And what’s just as notable is that the application of the fibreglass deck took only five days.
The team and their object
The NSF's Repair of Buildings and Bridges with Composites Industry- University Cooperative Research Centre is based at the University of Missouri at Rolla and the North Carolina State University. The Missouri researchers joined forces 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 US 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.
Strengthening for a large market in need
Instead of snarling traffic for two to three weeks while they repaired the crumbling deck, girders and guardrails by conventional methods, the workers used prefabricated plates and cages developed by a National Science Foundation (NSF)- supported university-industry partnership to finish the job in a mere five days.
"The exceptional versatility of the pultrusion process, which can produce virtually any constant-section profile, makes it possible to devise original reinforcement strategies to hit the market. The effectiveness of prefabricated pultruded FRP gratings as an internal reinforcement of concrete bridge decks has been demonstrated through extensive laboratory research," says Fabio Matta, a Ph.D. candidate in structural engineering who helped develop the new construction system.
The fibreglass-polymer composites made with vinylester resins 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. Matta estimates that the life expectancy of these bridges after the FRP improvements is 75 years. So far, none of the hundreds of drivers who use the bridge each day have had any complaints.