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University Develops ‘Bridge in a Backpack’

Tuesday, November 16, 2010

The University of Maine has developed a lightweight, corrosion-resistant, transportable “Bridge in a Backpack” that can be shipped in a bag to any construction site.

The system, for short- to medium-span bridges, uses Fiber Reinforced Polymer (FRP) composite arch tubes that act as reinforcement and formwork for cast-in-place concrete. The arches are easily transportable, rapidly deployable and do not require the heavy equipment or large crews needed to handle the weight of traditional construction materials, the university says.

Two Maine bridges have been rebuilt using the Bridge-in-a-Backpack technology: the Neal Bridge in Pittsfield, ME (pictured above), and the McGee Bridge in North Anson, ME. Six more of these arch bridges will be constructed in Maine over the next two years, the university says. In addition, two will be constructed in Massachusetts.

Development and Testing

The bridge technology was developed over eight years by the University of Maine’s AEWC Advanced Structures and Composites Center and introduced in 2009 by center director Habib Dagher. Project partners include the Maine Department of Transportation and the U.S. Army Natick (MA) Soldier Research, Development & Engineering Center.

The technology uses carbon-fiber tubes that are inflated, shaped into arches and infused with resin before being moved into place. The tubes then are filled with concrete, producing arches that are harder than steel, yet resistant to corrosion the inventors say.

Testing at the AEWC included structural characterization and modeling; fatigue testing for 50+ years of truck traffic, environmental durability testing for UV, fire, freeze-thaw and abrasion resistance; and instrumentation and field load testing.

“These arches capitalize on their inherent properties to transform vertical loads to internal axial forces, the superiority of concrete in sustaining compression loads, and the versatility and strength of composite materials,” ASCC says in a detailed flyer.

Licensing and Manufacturing

Advanced Infrastructure Technologies LLC, of Orono, ME, has licensed the bridge technology.

The fabrication of superstructure elements is a proprietary process that fuses several layers (including carbon fiber) with resin to create the composite material, the company says. The arches are transported to the job site, placed in position, covered in composite decking and filled with an expansive concrete, the company says.

AIT says the system lowers construction costs, extends structural lifespan up to 100 years, and has 50% of the carbon footprint of a concrete bridge.

All designs are engineered to exceed AASHTO load standards for single-span bridges from 25 feet to 70 feet and multi-span designs exceeding 800 feet, the company says.