November 3, 2000

Earthquake Mitigation Research Links NC State and Japanese Engineers

The sixth floor of an office building is a terrifying place to be during a major earthquake. However, thanks to the work of mechanical engineers from a consortium of institutions, including NC State and Osaka University in Japan, tall buildings will someday be much safer during earthquakes.

Dr. Mohammad N. Noori, department head of mechanical and aerospace engineering at NC State University, has been involved in this work for several years. Currently Noori and two colleagues from Japan, Dr. Tadatoshi Furukawa and Dr. Arata Masuta, are working at NC State this year to develop structural materials that can withstand the shaking associated with earthquakes. Furukawa arrived here September 1 and will stay until March; Masuta will stay one full year, from August 2000 to August 2001.

NC State is part of a US-Japan multi-university research team formed to study the development of new technologies, using smart materials, for earthquake mitigation of urban structures. The idea for the formation of this US-Japan cooperative project was inspired by the 1995 Kobe earthquake in Japan, one of the most damaging earthquakes in recent times. According to Noori, the devastation of the Kobe earthquake "encouraged the Japanese to make the very bold decision to develop major cooperative research between the US and Japan for coming up with some really radical, revolutionary ideas for earthquake mitigation." The main focus of this cooperation is on the use of emerging technologies, autoadaptive materials and structural health monitoring techniques.

Thirteen research institutions in the US are involved in the 10-year program, separated into two 5-year phases, with the Japanese Disaster Prevention Research Institute (DPRI). These institutions are Stanford University, CalTech, University of California-Berkeley, University of Southern California, University of California-Irvine, Texas A&M, University of Nevada-Reno, University of Illinois at Urbana-Champaign, Purdue University, Notre Dame University, Clarkson University, California State University and NC State University.

Many different aspects of earthquake mitigation are being studied through DPRI. Research at NC State involves Shape Memory Materials (SMAs), a class of materials that has been manipulated to exhibit a high damping, or dissipation of energy through motion, capacity. Such materials have the potential to withstand vibration much better than conventional materials. SMAs may be metal alloys, such as nickel-titanium or ferrous alloys, ceramics or polymers. Steel alloys may have the greatest potential for structural uses at the lowest cost.

SMAs are created by cyclic heating and cooling of an alloy using electric currents. This manipulation changes the properties of the alloy, making it "remember" its original shape after a distortion event such as an earthquake. Several challenges are associated with production of SMAs, including determination of material composition, difficulty of thermomechanical processing, fatigue life and, especially, cost and scale.

Much work remains to be done before cost-effective SMAs can be used in new construction. Noori and colleagues have high hopes for the development of these materials. "The exciting thing is that this program is aimed at developing a new generation of structural systems that can think and adapt themselves to the environment; they can react and self-repair," said Noori. These autoadaptive materials could sense environmental disturbances such as earthquakes and change their properties to alleviate the effects of these events.

The work being done in collaboration with DPRI represents a truly cooperative effort. According to Noori, engineers in the US have had more success in the development of autoadaptive materials, whereas Japanese engineers have superior techniques for health monitoring of structural elements of buildings. "The Japanese have done a lot of work in this area; in fact, the Japanese about six or seven years ago implemented a concept called structural control to build intelligent, earthquake-resistant structures. These structures, referred to as actively controlled systems, were the first generation of smart structures. There are about 20 buildings in Japan that have these computer-controlled active seismic absorption devices in them. Japan is the only country in the world where this technology has been implemented in structural systems. They're intelligent systems ? not in the sense that they're autoadaptive but in that they can resist an earthquake by adjusting themselves. This initiative is going to take it to the next step, which is completely intelligent structures."

Furukawa and Masuta are hoping to apply their research advances at NC State over the next year to several aspects of earthquake mitigation technology, but their primary interest is in health monitoring of existing structures. Because most buildings in Japan were constructed after World War II, the newer Japanese infrastructure is generally in better condition than US infrastructure. Therefore, maintenance and repair is more important than building new structures, at least for the next few decades.

The DPRI initiative was started five years ago, inspired by the damage in Kobe. The main goal in the next 10 years is to develop new concepts of structures, the next generation of structures that are intelligent, self-repairing and autoadaptive, Noori said.

-- rudd --

Technical Contact: Dr. Mohammad N. Noori, mnoori@eos.ncsu.edu
Media Contact: Linda E. Rudd, linda_rudd@ncsu.edu

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