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Saving lives, preserving infrastructure

The 15-by-20-meter E-Defense shake table simulated the effects of the 1995 Kobe Earthquake on two four-story buildings. Two hundred people observed the test, which was funded by Japan’s government.

Lehigh’s structural engineers took another step toward their goal of “sustainable infrastructure” recently when they helped conduct a successful experiment on the world’s largest earthquake shake table.

The test verified the superior performance of a reinforced concrete building system that contained earthquake-resisting technology developed at Lehigh’s ATLSS (Advanced Technology for Large Structural Systems) Center.

The ATLSS technology, a self-centering system, enables a building to survive an earthquake with no loss of life and little or no damage. It consists of reinforced concrete wall panels that are designed to “rock” during an earthquake with post-tensioned steel strands that, like a rubber band, pull the building back back to its original position.

The test was conducted at the Hyogo Earthquake Engineering Research Center, or E-Defense Center, in Japan. Lehigh researchers joined peers from the Network for Earthquake Engineering Simulation (NEES) in the U.S. and the National Research Institute for Earth Science and Disaster Prevention (NIED) in Japan.

The collaboration was led by E-Defense researchers, and the experiment was funded by the Japanese government.

A contest between new and conventional

E-Defense researchers built two full-scale models of a reinforced-concrete four-story building—one including the ATLSS system and one built with conventional reinforced concrete.

The E-Defense shake table simulated the 1995 Kobe Earthquake in Japan using recorded data from the actual event. The table also simulated the maximum-intensity earthquake expected in coastal California.

“The self-centering post-tensioned concrete wall system performed extremely well with very little damage under very strong earthquake ground motions,” ATLSS director Richard Sause and Wesley Keller, a Ph.D. candidate, reported.

“Many researchers were surprised by how well the self-centering wall system performed,” said Sause. “There was little to no damage. We think that’s the type of performance that should be expected. By contrast, the conventional reinforced concrete in the adjacent building was badly damaged.”

Preserving a community’s value

ATLSS researchers have studied post-tensioned self-centering structural systems for almost two decades in an effort to develop sustainable infrastructure that can survive earthquakes with little or no damage.

The goal, says Sause, is not only to protect lives but to ensure that building and transportation facilities remain operational after a major earthquake, thereby preserving the social and economic value of the affected community.

“Think of San Francisco,” says Sause. “What will happen when the next big earthquake hits? Twenty years ago, the question was, ‘Can we build structures that protect the lives of people?’

“Today, the question is, ‘Where are people going to live if there’s extensive damage to the city’s infrastructure?’ What will happen if, say, one-third or more of the people and businesses have to leave?”

The E-Defense Center test followed two years of planning and was part of a multi-year collaboration between NEES and NIED. Researchers from the University of California-Berkeley, UCLA, the University of Texas, Tokyo University, and Kyoto University also took part in the project.

Lehigh is one of 15 member institutions in NEES, which is funded by the National Science Foundation. The Lehigh NEES facility is directed by James Ricles, professor of structural engineering.

The director of E-Defense, Masayoshi Nakashima, received his Ph.D. from Lehigh in 1981. On March 25 in Sinclair Auditorium, he will give an address titled “Safeguarding Quality of Life: the Role of Large-Scale Testing.” The event, part of the Fazlur R. Khan Distinguished Lecture Series, is sponsored by the department of civil and environmental engineering and the department of art and architecture.

Photos courtesy of Wesley Keller

Story by Kurt Pfitzer

Posted on Thursday, February 17, 2011

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