The 75-footsingle-span Grist Mill Bridge in Hampden, Maine is the first in the nation to use the fiber reinforced polymer (FRP) tub-girders called GBeams™, designed at the University of Maine Advanced Structures and Composites Center. 

The patented GBeam technology results from research and development at the UMaine Composites Center, which licensed it to Advanced Infrastructure Technologies (AIT) Bridges, the university’s commercialization partner in Brewer, Maine. 

The GBeam technology is corrosion resistant and designed to last over 100 years with little to no maintenance. The composite girders, which are one-quarter the weight of steel girders, are a promising, sustainable, low-cost, easy-to-install alternative. 

The technology packs small, packs light, and can be deployed very quickly and easily, says Habib Dagher, executive director of the UMaine Composites Center. The girders are designed to be stackable, reducing transportation costs and lowering their carbon footprint. 

The practicability of the GBeam technology is further enhanced by the bolt system that connects the girders to the concrete deck, allowing the deck to be quickly removed for future replacement after 50 years without jackhammers. The ease of deck replacement will lower construction costs and minimize disruptive road closures. 

The many benefits of the composite GBeam technology are attracting interest from Departments of Transportation across the United States. The technology is already planned to be used in bridge replacement projects in Washington, California, Florida and Rhode Island. In Maine, the technology also will be used in the Hampden Twin Bridge project that will begin construction in 2022. Girders for these bridges will be fabricated by AIT and shipped to destinations nationwide. 

Funding for the research was provided by the U.S. Army Engineer Research and Development Center and the U.S. Department of Transportation through the Transportation Infrastructure Durability Center led by UMaine.