Hampden bridge reopening marks UMaine technology milestone

A small bridge with concrete sides over a rushing stream with an older bridge in the background

Courtesy / University of Maine The Grist Mill Bridge over Souadabscook Stream in Hampden, shown during construction, used composite GBeam technology developed by the University of Maine.

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By Staff

A ribbon-cutting at the Grist Mill bridge in Hampden recently marked more than just the bridge's reopening — the span, though only 75 feet long, is the first in the nation to use fiber-reinforced polymer girders developed at the University of Maine.

The GBeam technology was developed and patented at the University of Maine Advanced Structures and Composites Center and licensed to AIT Bridges, UMaine's commercial partner. AIT Bridges builds the beams at its Brewer production plant, and is now handling orders from as far away as California.

The girders are low-maintenance, durable and lightweight, a combination that could make it easier and less expensive to replace aging bridges across the U.S.

The event on the bridge over Souadabscook Stream celebrated "a significant milestone," said Habib Dagher, executive director of the UMaine Advanced Structures and Composites Center. "The Grist Mill bridge showcases the real-world applications resulting from cutting edge research in composite materials."

The corrosion-resistant composite girders are designed to last more than 100 years with little to no maintenance. They also weigh as little as a quarter of the weight of steel girders. They're so lightweight that rental cranes can be used to install them.

Yet they can handle heavy loads. Field testing involved more than 260,000 pounds of load carried by four Maine Department of Transportation trucks across the span. The two-day testing provided baseline performance data allowing UMaine researchers and AIT Bridges to refine the GBeam design, according to a news release about the ribbon-cutting.

“The girders are designed to be stackable, which reduces transportation costs and lowers their carbon footprint," Dagher said. "One flatbed truck can transport enough girders for four 70-ft long bridges, that is four Grist Mill bridges on one stretch-bed."

The technology also has bolts that connect the girders to the concrete deck, allowing the deck to be quickly removed for replacement after 50 years without jackhammers, which makes for lower costs.

Bruce Van Note, Maine transportation commissioner, said, “The big draw here is durability. Time will not take quite the same toll on the composite tub girders in this bridge. We expect this structure will need less maintenance over time and may last 25 years longer than its conventional counterparts. At MaineDOT, we believe sponsoring this new technology now will yield long-term benefits for Maine taxpayers and travelers.”

The girders are also being used in Maine on the Hampden Twin Bridge project, which will begin construction next year. But the Maine transportation department isn't alone — the technology is already planned for bridge projects in Washington, California, Florida and Rhode Island. The girders for all the projects will be fabricated in Brewer by AIT and shipped from Maine.

Funding for the research that led to the development of the technology was provided by the U.S. Army Corps of Engineers ERDC and the U.S. Department of Transportation through the Transportation Infrastructure Durability Center led by UMaine.

Dagher, who testified before the U.S. Senate earlier in May about the technology, said, "The R&D we are conducting at the Composites Center is delivering practical solutions to address our deteriorating infrastructure that is more durable, sustainable, cost-effective, and creating jobs right here in Maine.