Our Insights

Jul 28, 2020

Grist Mill Bridge – Hampden, Maine (2020)

Replacement of an aging steel bridge with a 75-foot single-span structure

Key Stakeholders

  • Owner: Maine Department of Transportation (Maine DOT)
  • Engineer: AIT Bridges in collaboration with T.Y. Lin International
  • Contractor: T-Buck Construction

Composite Solution

Utilization of five Fiber-Reinforced Polymer (FRP) GBeams, each 4'2" deep, supporting a 40'4" wide deck.

Performance Highlights

  • Achieved a load test inventory rating factor of 1.66, surpassing the design target of 1.04.
  • Demonstrated excellent deflection and fatigue resistance, meeting AASHTO standards.
  • Instrumented by the University of Maine and UMass Lowell for performance validation.

Benefits of Composite Materials

  • Corrosion-resistant and non-conductive, ideal for Maine's harsh climate.
  • Lightweight components facilitated accelerated construction and reduced transportation costs.
  • Projected 100+ year lifespan with minimal maintenance requirements.

BI Design & Engineering’s Contribution

  • Provided comprehensive design, engineering, and manufacturing services.
  • Leveraged proprietary GBeam technology for enhanced structural performance.
  • Collaborated closely with stakeholders to ensure project success.

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Trust the Testimonials

Stronger and Lighter, Naturally

"Composite materials like fiber-reinforced polymer (FRP) rebars offer higher tensile strength than Grade 60 steel at just a quarter of the weight—and unlike steel, they don’t corrode. This leads to longer service life for concrete structures. Among the various fibers used in FRP bars, basalt fiber stands out as a naturally sourced and sustainable alternative."​

Alvaro Ruiz Emparanza

Ph.D., P.E.; Founder & CEO, Ecotori, LLC

Streamlined Our Process

"Using basalt rebar streamlined our tilt-up wall construction process, offering exceptional ease of use compared to steel rebar. Its lighter weight, easy handling, and resistance to corrosion have translated into substantial labor savings, allowing us to achieve efficiency without compromising on structural strength."​

Brian Pratt

COO, McGarvey Development Company

Stronger And More Durable

"BFRP rebar is stronger and more durable than the minimum criteria set for GFRP bars and appears to be a viable alternative as a non-corrosive rebar option."​

Steven Nolan

Office of Materials, Florida Department of Transportation

Faster, Stronger, and Longer Life

"The benefits of this bridge-building method are threefold. First, the arches are an instant framework. Second, you don’t need any steel reinforcing bars or rebar, because the arches are twice as strong as steel. And third, the tubes protect the concrete from water and elements, extending the life of the concrete."​

Dr. Habib Dagher

Advanced Structures and Composites Center, U. of Maine

Same Building Method

"Whenever you introduce a new technology like this, contractors don’t always jump on it because there’s a fear that it’s going to be difficult to build. One of the beauties of [our composite bridge system] is that it’s built exactly the same way as you would build a steel girder or a concrete girder bridge."​

Bill Davids

Chair of Civil and Environmental Department, University of Maine

Lighter Means Faster

"A lot of our time-saving activities once we got to the superstructure were absolutely governed by the weight of the girders themselves and the ability to do more things at once"​

Brian Emmons

Project Manager, T Buck Construction

Expertise and Experience Drive Innovation

"It’s a combination of people who know how to build things, how to design things in the real world, plus our knowledge at the University in composite materials. Putting all that together really helped us develop the very unique secret sauce that I think will change how composites will be built in the future."​

Dr. Habib Dagher

Advanced Structures and Composites Center, U. of Maine

Faster Than Expected and No Issues

"Even though we knew this would be erected really quickly out in the field, the speed surprised us. It didn’t take very long for them to get their tubes in place, to get all the decking in place and start the backfill process. When you walk into a brand-new product like this, there is a certain level of risk. But there were just no issues at all with the construction."​

Mark Gaines

Washington State DOT Bridge & Structures Engineer

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