The Inflatable Bridge

A Fast-Build Bridge Could Replace Our Decaying Infrastructure

This August, Randy Gardner's construction crew blocked off a road in Anson, Maine, and set up what looked like a childrence bouncy castle. Neighborhood gawkers grew even more curious when a concrete tuck arrived on the scene. Despite the inflatable carbon-fiber tubes toylike appearance, Gardner explained to passerby, they provide the backbone to a new generation of sturdy bridges.

Roughly a quarter of the country's bridges need to be repaired or replaced, an setimated $140-billion project. The inflatable bridge system designed by engineres at the University of Maine, could get the job done cheaper - and faster. Workers unpack each carbon-fiber tube rolled up like a sock from a duffel back, inflate them, harden them with resin to produce sturdy arches, and fill them with concrete. Cover the top with sand and asphalt and its good to go.

The process uses fewer raw materials and minimal heavy machinery, saving 20 percent of the initial building costs. This summer, Gardner's crew put the tech to work and built a 28-foot bridge - typically a two-month job - in just 11 working days. Because the tubes protect the concrete from the elements, each bridge is projected to last 100 years - double the life of standard bridges. And if the concrete does break, the carbon-fiber tubes prevent an immediate disaster. "If one of the arches fails, it slowly sags instead of snapping," says engineer Habib Dagher of the University of Maine. "That's a warning to get out of there."

Advanced Infrastructure Technologies, the company that licenses the system, has contracts to replace eight bridges over creeks in New England. It expects to scale the arches up for 70-foot highway overpasses this spring and is investigating using the arhes to construct buildings.

-Susannah F. Locke

For more information on Advance Infrastructure Technologies go to http://www.aitbridges.com/