December 30, 2008

Elastic Alloy May Save Bridges From Earthquakes

An engineering team at the University of Nevada, Reno has developed the prototype for a bridge that is more resilient to damage caused by earthquakes.

The 100-foot-long bridge consists of an alloy made of nickel and titanium, which helps give it more elasticity.

The mock bridge is a quarter-scale replica of what it would look like in real-life.

"The nickel-titanium rods replace steel bars in critical segments of bridge columns," said engineering professor M. Saiid Saiidi.

"These are the type of materials that have a memory," Saiidi said of the alloy, which he nicknamed "nitinol."

"They remember how they were before the earthquake happened, so they tend to maintain their shape. They undergo lots of deformation during the earthquake but they go back where they were before."

The bridge was put to the test as it was subjected to 10 seconds of shaking that created the equivalent of an earthquake of magnitude 8.0, researchers said.

It was built to resemble actual circumstances such as the Northridge quake, which struck at 4:30 a.m. on January 17, 1994 with a magnitude of 6.9, killing fifty-seven people and injuring more than 9,000.

During the 10-second quake simulation, 400 movement sensors mounted at various critical points along the bridge measured the structure's response.

Researchers said the alloy is more elastic than traditional concrete and steel formations, which doesn't yield to the force of an earthquake.

"My next plan is to implement this in some real bridges, perhaps in California," Saiidi said.

"The ultimate goal is to improve the emergency response by keeping bridges open, and minimize interruption to the highway network operation to avoid major economic losses," he said.


Image Caption: The bridge is a test bed for cutting-edge construction technologies of the future with many of the new materials being tested in a bridge system for the first time. Photo by Mike Wolterbeek.


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