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Carbon-fiber Wrap

This earthquake warning sign was posted at the entrance to the basilica at the Carmel Mission in Carmel, Calif. The basilica started getting a seismic retrofit in 2012.

© Michael Fiala/Reuters/Corbis

It makes sense to consider earthquake resistance when you're building a new structure, but retrofitting old buildings to improve their seismic performance is just as important. Engineers have found that adding base-isolation systems to structures is both feasible and economically attractive. Another promising solution, much easier to implement, requires a technology known as fiber-reinforced plastic wrap, or FRP. Manufacturers produce these wraps by mixing carbon fibers with binding polymers, such as epoxy, polyester, vinyl ester or nylon, to create a lightweight, but incredibly strong, composite material.

In retrofitting applications, engineers simply wrap the material around concrete support columns of bridges or buildings and then pump pressurized epoxy into the gap between the column and the material. Based on the design requirements, engineers may repeat this process six or eight times, creating a mummy-wrapped beam with significantly higher strength and ductility. Amazingly, even earthquake-damaged columns can be repaired with carbon-fiber wraps. In one study, researchers found that weakened highway bridge columns cocooned with the composite material were 24 to 38 percent stronger than unwrapped columns [source: Saadatmanesh].

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