Ten years ago, after a lengthy period of being tested on bridges throughout the country, fiber-reinforced polymer composites—touted for their lightness, longevity and resistance to corrosion compared with traditional materials—seemed poised to enter the U.S. mainstream bridge-building market.
Ten years later, however, FRPs are still on the fringe. An entrenched business culture resis-tant to change, up-front costs and a lack of codes have been significant barriers to market entry. But thanks to recent developments in policy and research, advocates believe composites may—finally—be ready for prime time. Today, the increasing awareness of carbon footprints and the life-cycle maintenance benefits of fiber-reinforced polymers (FRPs), not to mention corroded bridges, have forced a second look at FRPs.
“The voice of reason is starting to be heard,” says Thom Johnson, a manager at Ashland Performance Materials, Dublin, Ohio, which provides resins for FRPs. Language in the pending six-year federal transportation bill, H.R. 1682, he notes, “requires a state, as a condition of receiving federal-aid highway funding, to develop and implement a highway bridge management system that meets certain requirements,” such as to “identify corrosion mitigation and prevention methods to preserve its highway bridges” and “establish a project maintenance program to extend the life of such bridges.”
Composites are much further along in the marine world, where they have all but replaced timber for pilings, notes Robert Greene, president of Lancaster Composite, Millersville, Pa. “I’m encouraged by the awareness of this product among transportation departments and how it has increased in the last three to five years,” he says.
A big push in gaining acceptance came from the U.S. Navy, which wrote a thorough specification for FRP piles. “It’s a big plus, having a third-party certification that any other government agency can apply or refer to,” Greene adds.
A code recently was approved by the American Association of State Highway and Transportation Officials for FRP rebar and pedestrian bridges. “We presently are working on codes for bridge decks and composite repairs of concrete,” says Paul Liles Jr., chairman of the AASHTO subcommittee on composites. The American Composites Manufacturers Association has also been working with the American Society of Civil Engineers on development of a technical standard.
“We’re a small entity, but the seeds are being sown,” says Dan Richards, president of Durham, N.C.-based Zellcomp Inc., an ACMA member. He estimates it will take another three or four years to get AASHTO codes for beams and decks.
Another legislative hurdle is a Federal Highway Administration rule that requires a proprietary material to meet various requirements before it can be used on a project. “Almost all we do comes up against this snag,” says Roberts.
The sole-source rule is a snag partly because there are not many FRP deck producers. But Sami H. Rizkalla, director of the Constructed Facilities Laboratory at North Carolina State University, is confident FRPs will go mainstream. “It will. [But] any material takes a while to become common,” he says.
John Busel, ACMA’s composites growth initiative director, says, “There has been progress. There is interest, but it comes down to projects.”
In 2000, Hardcore Composites, New Castle, Del., won a $7-million award to build 100 FRP bridge decks in Ohio (ENR 1/31/00 p. 24); however, the firm filed for bankruptcy a few years later. A 2006 report on the status of FRP decks by the Transportation Research Board’s National Cooperative Highway Research Program cited problems with Hardcore’s fiberglass-composite deck installations, including at a Dayton, Ohio, test site.
In 1999, the Ohio Dept. of Transportation, Army Corps of Engineers, Ohio University and the Universities of Cincinnati, Maine and Kentucky collaborated on an analysis of four FRP decks on Dayton’s heavily traveled First Salem Avenue Bridge. One type consisted of double trapezoid and hexagonal components shaped by poltrusion. The others included a fiberglass-composite deck, a hollow-core sandwich system and a system combining FRP panels with concrete and polymer rebar.
The first two decks experienced thermally induced deformation, says Bahram Shahrooz, a University of Cincinnati structural engineering professor. In the spring, the deck layers debonded. The latter two decks are still in use today.
Other test sites also featured learning curves. The 40-ft-long Triphammer Road Bridge in Avon, N.Y., was touted in 2000 as being the nation’s longest plastic bridge. “There were only a few manufacturers of FRP decks,” recalls Ron Centola, branch manager for Goodkind & O’Dea Inc. and project manager for the $515,000 bridge.
The New York Dept. of Transportation had to develop a performance specification for the panels. “The manufacturer had never built a bridge of this size, and they underestimated the amount of resin they needed,” he says. That “manufacturer” was Hardcore, but the bridge is holding up well 10 years later, he says.
In 2003, Wisconsin tried another first: a stay-in-place composite-deck forming system placed over prestressed-concrete girders on a Highway 151 bridge. Polymer composites were used for the concrete deck’s upper reinforcement grid and rebar.
Larry Bank at the University of Wisconsin-Madison led the research team. The cost was about 60% more than a conventional system, but ease and speed of installation would have meant a 57% savings off the bid price; however, the bid price added the cost of the system to traditionally assumed costs, he says. Also, Bank says, “We used an already designed, off-the-shelf system that was overdesigned for the task, but [it was] the only one readily available.”
A Canadian effort has yielded positive results in strengthening existing bridges. In 1999, Manitoba installed glass-fiber-reinforced polymer bars on the Tourand Creek Bridge, south of Winnipeg. A series of grooves in the underside of the two-lane bridge were filled with ¼-in.-dia polymer and epoxy resin.
|At least twice as long as conventional.|
|Fifty percent less pollution.|
|Requires no heavy equipment.|
|Bridge erection often can occur in days, not weeks.|
“We’ve done five bridges since then,” says Ruth Eden, director of structures for the province’s Infrastructure and Transportation Dept. While the cost of each bridge was $150,000 to $200,000 compared with traditional replacements at $2 million each, service life has been extended by 15 to 20 years. But FRPs are not a panacea. “We wouldn’t have done it if the foundations weren’t solid or if the stringers were cracked,” Eden says.
The emerging leader in the composites-infrastructure evolution may well be Maine, thanks in part to Gov. John Baldacci’s (D) staunch support. Martin Grimnes, a textiles and composites veteran, founded both Orono, Maine-based Harbor Technologies Inc. and the Maine Composites Alliance.
“The boat-building and marine industries are significant for Maine, and they have done composites for years,” Grimnes notes. Harbor Tech helped develop the hybrid composite beam invented by John Hillman. “We’re looking to tie in components, like the [Hillman] beam, to form a complete system solution,” he says. If a bid competition is based on total installation and systems costs, rather than specific materials costs, composites can gain an edge, he adds.
Harbor Tech works with the University of Maine’s Advanced Structures and Composites Center, where researchers developed the “bridge in a backpack”. With Maine DOT, the Maine Composites Alliance plans to invite other DOTs to see the bridge-in-a-backpack, the Hillman beam as well as storm drains and culverts featuring composite linings, says managing director Steven Von Vogt.
“This is a banner year” for FRP projects, says Dale Peabody, Maine DOT research manager. “The more we get these projects out, the more our engineers will be comfortable.”