'Bridge-in-a-backpack' coming to Belfast
Belfast — A chasm near the intersection of Herrick Road and Perkins Road in Belfast — until about a month ago, the location of a nondescript bridge over the Little River — is to be the site of a new kind of bridge, one that uses concrete-filled, carbon-fiber tubes developed at the University of Maine's AEWC Advanced Structures and Composites Center.
The technology, known as "bridge-in-a-backpack," because the components can be moved without requiring heavy machinery, uses flexible tubes of carbon fiber material that are inflated with air, cured with a resin, then filled with concrete on site to form a structural backbone for the bridge.
The bridge in Belfast will be among the first in the world to use the new technology. The Maine Department of Transportation rebuilt the Neal Bridge in Pittsfield with a "bridge-in-a-backpack" in 2008, and the town of North Anson replaced the aging McGee bridge with one incorporating carbon-fiber tubes in 2009.
As part of the state's 2010-11 budget, the Legislature gave MDOT $6 million to build "bridge-in-a-backpack" bridges. In addition to the Belfast bridge, two other "bridge-in-a-backpack" projects are currently under way, in Auburn and Bradley, and others are planned for Caribou and Westbrook.
AEWC, formerly known as the Advanced Engineered Wood Composite Center, began developing the technology in 2001, and extensive testing has reportedly demonstrated that the arches are stronger than steel and resistant to corrosion.
In 2009, the University of Maine licensed the "bridge-in-a-backpack" technology to Orono-based Advanced Infrastructure Technologies.
According to Nate Benoit of MDOT, the state purchased the technology for the Herrick Road Bridge, including the carbon-fiber tubes, from AIT. The tubes are being manufactured by Kenway Corporation in Augusta and will be made rigid before they are transported to the site to be installed, he said.
Benoit said the Belfast site was chosen in part because of the large distance between the road surface and the stream bed, which needs to be substantial to accommodate the construction technique.
After the tubes are erected on concrete footings at the site, the arches will be overlaid with a corrugated sheathing. Concrete walls will then be erected along either flank and the space filled with a thick layer of gravel. The road surface will be applied on top of this substrate.