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Two Layer Composite Provides Earthquake Resistance

University of Arizona - Hamid Saadatmanesh wasn't dressed in a white lab coat and working in a university laboratory at that serendipitous moment when a revolutionary concept for protecting buildings and other structures from earthquakes and explosions flashed across his consciousness.

He was at home, lying on the sofa in front of the TV.

On the screen, a strong man had placed a masonry block on his chest. Then his assistant swung a sledgehammer over his head and smashed the block with terrific force. The block shattered, but the strong man got up unhurt and basked in applause.

It was one of those "Eureka" moments.

"I was so excited, I jumped off the sofa," Saadatmanesh recalls. "I suddenly realized the block is a sacrificial element and that the same concept would work to protect the load-bearing elements of a building, bridge, or other structure."

"If he had been hit directly with the sledge hammer, his chest would have been crushed," Saadatmanesh notes. "Instead, the block absorbed the energy by shattering."

First thing the next morning, Saadatmaneh rushed to his office and called a National Science Foundation program director and discussed the concept with him. It was one of those, "Why didn't I think of that?" ideas. Funding followed shortly.

Now Saadatmanesh, a professor of civil engineering at The University of Arizona in Tucson, and his graduate students are performing preliminary dynamic tests with simulated seismic shock loads and blast loading. "The initial indications are that this should be a superior technique," he says.

For the past decade, Saadatmanesh and his colleagues have been wrapping pillars, walls, and other load-bearing structures with advanced fiber composites to increase their ability to withstand earthquakes.

His new concept for protecting structures from shock loads such as those encountered in earthquakes and blasts continues this work by using a two-layer advanced composite material.

The outside layer is a sacrificial element that will fail - like the stuntman's masonry block - and absorb the peak shock energy. The second layer will add strength to the structure to additionally help it withstand the loading.

"Structures absorb energy under shock loading and they have to somehow dissipate that force," Saadatmanesh explains. "Usually they get rid of this energy by shattering and collapsing. But by sticking in an element that is designed to fail, we are able to absorb the peak load and protect the underlying structure."

"In a way, this is like a bullet proof vest for beams and walls," he says, noting that the material, which is only 1/8- to 1/4-inch thick, can easily be wrapped around load-bearing beams, columns and walls in existing structures.

Contact: Hamid Saadatmanesh, 520-621-2148, hamid@u.arizona.edu

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