Tuesday, October 13, 2009

Bridges of Black Plastic Manicotti

The [Neal] bridge is newer than most, as suggested by the still-black asphalt and the fresh galvanized gleam of the guardrails. But it’s what is underneath that really makes the bridge stand out.

Rather than steel or concrete beams, the structure consists of 23 graceful arches of carbon- and glass-fiber fabric. These are 12-inch-diameter tubes that have been inflated, bent to the proper shape and stiffened with a plastic resin, then installed side by side and stuffed with concrete, like giant manicotti. Covered with composite decking and compacted soil, the arches support a standard gravel-and-asphalt roadway.

The bridge is the first of what its designers, about 50 miles up the road at the University of Maine in Orono, hope will be many of its type, combining composite materials with more conventional ones like concrete. With an estimated 160,000 of the nation’s 600,000 road bridges in need of repair or replacement, if it or other hybrid designs catch on, they could mark a breakthrough in the use of fiber-reinforced plastics, known as F.R.P., on highways. __NYT_via_ImpactLab
These new plastic-fiber bridges are lighter for the same strength -- thus allowing for heavier live loads (traffic). How well they will age in different climates is a question that will have to be answered with more testing, and time.

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