1 February 2002
Plastic makes stronger span?
Sugar Grove, Va.—What do you get when you combine plastic with some civil engineers? The answer is a bridge spanning the Dicky Creek in Sugar Grove, Va.
The bridge, a 12-meter, two-lane, clear-span bridge supported by eight 92-meter-deep composite beams supplied by Strongwell Corp. of Bristol, Va., meets U.S. standards for a bridge capable of carrying full tractor trailer traffic.
While the future for bridges may be in plastics or fiber-reinforced polymer, one big hurdle for widespread use of polymer composites is the ability to manufacture the large composite beams at a cost competitive with steel. Strongwell's beams, strengthened with a combination of glass and carbon fibers, were developed under a NIST Advanced Technology Program project to enhance the mechanical properties of the material, optimize beam shape, and establish design standards and load capacities.
Bridge engineers have high hopes for polymer composite bridges. Composite beams can be much lighter and stronger than the steel beams they replace, as well as easier and faster to install (because of their light weight.) In addition, they should be considerably more durable and maintenance free than steel.
Durability is a major benefit-Federal Highway Administration studies indicate that nearly 30% of bridges in the U.S. are obsolete or structurally deficient and that bridge maintenance/repair is a major expense for many state and local transportation departments.
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