Composite Beams Designed to Enhance Bridge Durability and Reduce Life-Cycle Costs

• Prototype bridge beams made of carbon- and glass-reinforced polymer composites have passed laboratory tests and have been installed successfully on a Virginia bridge as an offshoot of work done by Strongwell Corporation, Bristol, Va., under the NIST Advanced Technology Program. The lightweight, corrosion-resistant beams are expected to improve bridge durability and reduce overall life-cycle costs.

Composites (hybrids of two or more materials) are attractive for infrastructure applications--bridges, buildings, and other large structures--because they are lightweight and resistant to rust and corrosion, but they are also expensive and difficult to engineer into structures of appropriate shape and size with adequate stiffness. Strongwell Corp. is designing and manufacturing bridge beams made of polymer composites that consist of glass and carbon fibers bound by a resin, which should last longer and be maintained more easily than the concrete and steel now used. Strongwell, which is using ATP co-funding to enhance the mechanical properties of the material, optimize beam shape, and establish design standards and load capacities, has designed and manufactured an 8-inch-high prototype bridge beam and continues to work toward production of a 36-inch-high beam. Strongwell worked with the Georgia Institute of Technology to optimize beam shape for torque resistance and to increase the beam's stiffness, eliminating the need for braces and also optimizing costs. The prototype beams performed well in tests for fatigue, creep (stretching under tension), and strength under static loading.

The project has attracted the interest of transportation officials in a number of states, including Virginia. In an offshoot to the ATP project, 24 subscale beams were installed successfully in the replacement of the Tom's Creek Bridge in Blacksburg, making it one of the first U.S. vehicular bridges to use hybrid composites as the primary load-bearing structure. Long-term field tests will indicate whether taxpayers can reap the expected benefits of reduced fabrication, installation, and maintenance costs and fewer traffic delays associated with bridge repair and replacement. Companies in other industries also have inquired about using composite structures in applications such as offshore oil platforms and wooden decks.

ATP funding: $2,000,000
Non-ATP funding: $1,153,000

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September 1997