Fort Bragg Builds Sustainable Bridge of the Future

M-1 Tank Crossing Plastic Bridge at Fort Bragg.

SOURCE: Fort Bragg Directorate of Public Works · RELEASED: July 9, 2009 · AUTHOR: Erin Barstow

Fort Bragg continues to lead the way in innovative Army sustainable design and development with the recent construction of the world’s first recycled content bridge built to bear the weight of a tank.

History was made on the morning of 11 June when the bridge successfully endured multiple passes of a 71-ton M1 Abrams Main Battle Tank, supplied by the North Carolina Army National Guard, with outstanding results. “The load-testing was the final ‘proof in the pudding’. It actually performed even better than expectations,” said Rich Lampo, Materials Engineer for the U.S. Army Engineer Research and Development Center (ERDC), Construction Engineering Research Laboratory (CERL) in Champaign, IL.

The bridge consists of 94 percent recycled materials including glass, vehicle bumpers and approximately 85,000 pounds of high-density polyethylene plastic. That’s equivalent to roughly 550,000 one-gallon plastic milk jugs which, laid end-to-end, would extend nearly 82 miles. A model of sustainability, the bridge diverts valuable commodities from the solid waste stream, resists rot and damaging insects without the use of chemical treatments and requires minimal maintenance throughout its lifecycle. Furthermore, the structure is cost-competitive to standard treated timber bridges on a first-cost basis and has a life expectancy twice as long.

The concept of recycled content bridges began in the late 1980s when Lampo combined efforts with Dr. Thomas Nosker of Rutgers University, NJ, to construct lumber materials from recycled plastics. “We saw that there were possibilities beyond park benches and picnic tables. Those types of things are okay, but if you want to start utilizing large quantities of these recycled materials, then we needed to do civil construction and civil structures,” said Lampo.

The American Society for Testing and Materials (ASTM) International was enlisted to assist in creating specifications and standards for the resulting new material and, in 1998, a pilot project was carried out at Fort Leonard Wood, MO, to replace the superstructure of an existing wooden bridge. The bridge’s lifecycle savings and minimal maintenance requirements were estimated to produce a full return on investment in less than eight years; however, the high upfront cost of the recycled materials made it unlikely that the design would be competitive in mainstream construction markets.

The Rutgers University team, in partnership with CERL, McLaren Consulting Engineers, NY, and Axion International, NJ, returned to the drawing board to develop a more resource-efficient I-beam design that would reduce the amount of material used in each beam without compromising its structural integrity.

“You are paying for these materials by the pound, so if you could remove material that’s not contributing to the beam’s strength—which is the concept behind an I-beam—then you could reduce the cost while still carrying the same load,” explained Lampo.

In March 2007, Lampo approached Fort Bragg with a proposal to replace one of the installation’s existing wood timber bridges with a recycled content bridge. Recognizing the inherent value and far-reaching applications of this design, Fort Bragg Directorate of Public Works (DPW) representatives readily agreed, challenging Lampo and the team to design one capable of accommodating tank traffic for installation training exercises. Once the design was in place, construction was completed under contract in less than 10 weeks.

“This project gives Fort Bragg the opportunity to increase soldiers’ readiness by expanding training capabilities and provides a cost-effective way to access training areas on the installation without having to expend large sums of money to repair these structures,” said DPW Civil Engineer Darryl Butler. “It allows us to be at the cutting-edge of technology, and is definitely something that Fort Bragg and the Army will benefit from immensely.”

This landmark project was achieved through the coordination of military, civilian and private contractor sectors, with the Office of the Secretary of Defense’s Corrosion Prevention and Control (CPC) Program funding the bridge’s design and remote long-term remote monitoring, and ACSIM’s Installation Technology Transition Program (ITTP) covering construction and subsequent load testing.

Lampo envisions future recycled content bridge designs will include modular mix-and-match components capable of adapting to varying structural and load requirements. “What we are striving for is that recycled content bridges will become the Army and Department of Defense standard for constructing bridges of this type. There’s got to be thousands of bridges nationwide that are candidates for this type of design,” said Lampo. “If these structures are cost-competitive on a first-cost basis, use recycled plastics, don’t require any kind of chemical treatment, and require virtually no maintenance, why would you want to build bridges with anything but these materials?”

A formal dedication ceremony for the bridge is scheduled for 20 August. A second plastic composite tank bridge recently constructed on Fort Bragg with funds from the Installation Management Command (IMCOM) Army Transportation Infrastructure Program (ATIP) is currently being prepared for load testing. A third one is planned for Fall 2009.

For more coverage of the new plastic bridge at Fort Bragg, Click Here.