Quake experiment tests shake-proof metal

WASHINGTON Mon Dec 29, 2008 8:08pm GMT

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WASHINGTON (Reuters) - A 10-second experiment using an "elastic" alloy made of nickel and titanium may point to a way help save bridges in earthquakes.

The new alloy greatly reduced damage to a 100-foot-long (30-m-long) model concrete bridge in the experiment, designed to replicate the 1994 Northridge quake that killed 57 people and caused widespread damage near Los Angeles in California.

The team at the University of Nevada, Reno, shook the bridge for 10 seconds in a simulation of a magnitude 8 quake. In Northridge, that was long enough to flatten bridges and overpasses.

But this bridge, reinforced with the nickel-titanium alloy, remained upright and, although the concrete suffered some residual damage, the basic infrastructure was intact.

Engineering professor M. Saiid Saiidi said the nickel titanium alloy, nicknamed "nitinol," is elastic.

"These are the type of materials that have a memory," Saiidi told Reuters in a television interview.

"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 facility at the University of Nevada is the largest of its kind in the United States and the only one, engineers say, capable of replicating and even exceeding the power of giant quakes such as the Northridge temblor.

The Northridge quake struck at 4:30 a.m. on January 17, 1994 with a magnitude of 6.9.

Fifty-seven people were killed and more than 9,000 injured. The structural damage to buildings and freeways cost an estimated $20 billion.

The experiment involved three 50-ton capacity shake tables activated in unison to replicate the effects of the earthquake.

Sensors attached to various points of the bridge carried data to computers for analysis throughout the simulation. Early results indicated that the nickel titanium had minimized damage.

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

"I've already talked to engineers over there and once we find out how these materials perform in a laboratory environment we're going to take them to the field and implement them on a real bridge and hoping that we'll have data to demonstrate that they do work and then they can be adopted for real bridges in the future, potentially."

(Editing by Maggie Fox and Cynthia Osterman)

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