According to the Federal Highway Administration’s (FHWA) National Bridge Inventory, 147,870 of the 607,751 bridges in the United States are deficient. Of these, 63,522 are structurally deficient and 84,348 are functionally obsolete bridges. A structurally deficient bridge is a bridge that has critical load-carrying elements in poor condition. A functionally obsolete bridge is a bridge that fails to meet current standards for bridge construction (like lane width or load capacity).
The Bridge-in-a-Backpack building method was created to resolve this issue. The Bridge-in-a-Backpack system, which was developed at the University of Maine’s Advanced Structures and Composites Center, incorporates new bridge technology that can meet the demands of an ABC program. A company called Advanced Infrastructure Technologies licensed and commercialized the technology. The system uses carbon fiber reinforced polymer (FRP) composite tubes to form arch spans. These tubes are resistant to corrosion, provide external reinforcement, and add durability and strength to the concrete superstructure. This technology is revolutionary because it expedites the building process and improves the quality and longevity of bridges.
“The name Bridge-in-a-Backpack came about because the composite tubes were designed to be rolled up and stuffed in duffel bags in order to be easily transported to the construction site. Once at the site, the tubes would be rolled out, inflated and then set into a frame that bends it into an arch. After the tubes are shaped to the required geometry they are infused with resin using a vacuum-assisted transfer molding process and allowed to cure.
Once cured, the lightweight arches are placed into the abutments and covered with corrugated FRP decking panels. The arches are then embedded into the concrete foundation and the arch tubes are filled with an expansive concrete. Headwalls are installed and dirt fill is then compacted on top of the FRP decking and paved over with asphalt. Total construction time from the demolition of the existing bridge to the completed Bridge-in-a-Backpack can be completed in a matter of days. “
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