You wouldn’t expect to find a bridge with state-of-the-art GFRP decking on a two-lane, rural road. But there’s one on Elizabeth Church Road in Morgan County, Tenn. Constructed through the efforts of a public-private partnership, the structure is intended to demonstrate the benefits of composite materials for bridge.
There’s a real need for this solution. The American Society of Civil Engineers estimates that 7.5% of the 617,000-plus bridges in the U.S. are structurally deficient and need repair. FRP composites offer a proven, low-cost, low-maintenance option.
Composites have been used for bridge deck projects for more than 20 years and have exceeded all of the performance and safety standards set by the American Association of State Highway and Transportation Officials (AASHTO), according to John Unser, vice president of program and project management at Composite Applications Group (CAG) and a consultant technology impact manager with IACMI – The Composites Institute®. The problem is that many highway directors and managers, especially those from smaller jurisdictions, still aren’t familiar with the technology.
The public and private entities that built the Morgan County bridge want to change that. Composite Applications Group, headquartered in Tennessee, and Structural Composites Inc., based in Florida, had already been exploring possible infrastructure opportunities with IACMI when the coronavirus pandemic hit. When normal business slowed and funding through the Paycheck Protection Program became available, the time seemed right to pursue a demonstration project. Because of its experience working with industry and government, IACMI took the lead.
Jeff McCay, CEO of CAG, discussed the composite bridge technology with Brian McKinney, president of McKinney Excavating in Tennessee. McKinney introduced McCay to Joe Miller, Morgan County’s highway superintendent, who was very interested in testing a composite bridge deck on one of the county’s distressed bridges. “One of the things that we think is pretty critical, especially in rural areas, is finding a champion,” McCay notes.
The group chose a bridge that is 25 feet wide and just 16 feet long. That short length was desirable since the Tennessee Department of Transportation does not have to sign off on bridges less than 20 feet long. (Concerns about risk mitigation may hamper state DOTs from approving new technologies.)
The bridge partnership then expanded to include researchers from the University of Tennessee’s Fibers and Composites Manufacturing Facility. They put together a system of fiber optic sensors, which was embedded in the composite decking during manufacturing, plus a module that enables the university researchers to monitor the structure over time. The sensors, developed by Luna Innovations Inc., will measure strain from mechanical loading and thermal/hygroscopic (humidity) loading from thousands of points.