The first technology, the so-called “bridge in a backpack,” features rigidified inflatable composite arches. Developed with funding provided through the U.S. Army Natick Soldier Center, the U.S. Federal Highway Admin. (FHWA) and the Maine Department of Transportation (MDOT), the arch materials are fibrous tubes that can be folded and shipped in a bag to an installation site, shaped to fit bridge geometry, infused with resin, allowed to cure overnight, and then filled with concrete. The lightweight hollow tubes are easily installed and act as a stay-in-place form and a protective layer for the concrete. UMaine has two patents pending on this technology. Working with MDOT and a local contractor, the school recently used the technology to construct the Neal Bridge in Pittsfield, Maine (see “Engineering Insights,” at right).
A second bridge construction innovation, which uses composite beam forms filled with concrete, is being commercialized by Harbor Technologies LLC (Brunswick, Maine). The HC Beam hybrid-composite-concrete bridge system combines the durability and flexibility of a composite stay-in-place form with the low cost and functional advantages of concrete and steel. A 70-ft/21.3m bridge girder was on display at the AEWC lab. This girder could be trucked as an empty composite box weighing 6,000 lb/2,727 kg, which then would be filled with concrete on site, as opposed to 50,000 lb/22,727 kg for a precast concrete girder. The company plans to use HC Beams in the construction of a 500-ft/152m long bridge in Boothbay Harbor, Maine, this summer.



