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$2-million earthquake engineering research grant from NSF to help ATLSS develop self-centering steel frame systems

The ATLSS Research Center has received a $2-million grant from the National Science Foundation to develop revolutionary steel-frame structural systems that can enable buildings to survive earthquakes without damage.

Richard Sause, ATLSS director and principal investigator, said the four-year international project represents an effort to "develop technology for future buildings in order to eliminate billions of dollars in future earthquake damage.

"We're trying to leapfrog past existing steel-frame construction systems to develop new ways of connecting steel-frame members to eliminate structural damage under anticipated earthquake loads," said Sause.

"The building design profession has been progressing from the point of accepting building damage in earthquakes, as long as injuries and loss of life are minimized, to the point of seeking significantly reduced damage. Our research is seeking to advance to the point where, if you look at a steel-frame building before and after an earthquake, you will see no significant difference."

The project's participants include researchers from Princeton and Purdue universities and Taiwan's National Center for Research in Earthquake Engineering.

The project involves numerical simulations, laboratory experiments, and the use of advanced sensors, advanced materials, and information technology.

Experiments will be performed at the ATLSS Center's Real-Time Multi-Directional Testing Facility (RTMD), one of the largest of its kind in North America, which subjects structures to loads and loading rates similar to what they would sustain during an earthquake.

The RTMD facility is funded by NSF through its George E. Brown Jr. Network for Earthquake Engineering Simulation (NEES), which is a consortium of 15 universities, including Lehigh, that conduct research on the effects of earthquakes and tsunamis on buildings, bridges, utility systems and other infrastructure.

Co-principal investigators on the NSF project include James Ricles, professor of structural engineering and director of Lehigh's RTMD facility, and Maria Moreyra Garlock, who earned a B.S. in civil engineering from Lehigh in 1991 and a Ph.D. in structural engineering in 2002 and is now an assistant professor at Princeton University.

The performance of steel buildings during earthquakes took on renewed urgency among structural engineers following the Northridge-Los Angeles Earthquake of 1994, which killed 57 people, injured more than 1,500 and caused $44 billion in damage.

More than 25,000 dwellings were rendered uninhabitable by the Northridge Earthquake, and some 7,000 buildings were deemed unsafe to occupy and were "red-tagged" until damage was corrected.

Some of the red-tagged structures were steel buildings which engineers had anticipated would better withstand earthquakes, said Sause.

The new project was one of 10 projects to be funded, out of 110 proposals submitted, through NSF's NEES research program in fiscal year 2005. NSF disbursed a total of $9 million to the 10 successful proposals.

The goal of the Lehigh-led project is to develop an earthquake-resistant steel frame that "self-centers" after a seismic event, said Sause.

"A self-centering system will stand 'plumb' at the end of an earthquake," said Sause, "rather than be permanently deformed or lean in one direction or the other. Many buildings constructed with current technology are likely to permanently deformed after an earthquake. The process of straightening a building after an earthquake can be difficult, expensive or impossible, and often the damaged structure has to be demolished.

"There may be other applications of this technology, as self-centering buildings may better withstand blasts and other severe loads."

In the 1990s, Sause collaborated with Stephen Pessiki, associate professor of civil and environmental engineering, on research into similar systems made of pre-cast concrete. Felipe Perez, who earned a Ph.D. in civil engineering from Lehigh and is now an engineer in Los Angeles, also collaborated on those projects.

Self-centering steel-frame systems eliminate damage to critical regions of a steel frame through the controlled opening of gaps at column-to-beam and other connections, said Sause.

"The connections are initially clamped together with pre-stressing force," said Sause.

"The clamping force is overcome during an earthquake, but each connection returns to its original position after the event and controls the final position of the structure with no permanent deformation to the structure. As the gaps open at the connections during the earthquake, the connected surfaces undergo a rocking motion, and the components of the connections, instead of being fixed together, move relative to each other, allowing the energy of an earthquake or a similar load to dissipate."

Posted on Saturday, March 05, 2005

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