System Based On Human Biomechanics to Help Protect Structures From Earthquake Damage

BUFFALO, N.Y. -- A University at Buffalo engineering professor's life-long fascination with the biomechanical abilities of humans has led to his development of the first energy-dissipation system for man-made structures that is based on the biomechanics of the human body.

UB has licensed the "smart" new technology, called Real-Time Structural-Parameter Modification (RSPM), to Enidine, Inc. of Orchard Park, N.Y.

Enidine manufactures and markets industrial shock absorbers, seismic dampers and vibration isolators with applications in robotics, materials handling, packaging, defense, aerospace and seismic systems.

"This marriage of the research capabilities of UB and the commercialization capabilities of Enidine provides us with an exciting opportunity to develop leading-edge technology into a successful, commercial product," said Malcolm Gibbins, executive vice president of Enidine. "RSPM will open up design options and expand the seismic-energy mitigation potential for earthquake-protection markets in the future."

In addition to seismic-mitigation products for new and existing structures, the new technology may be useful for other systems, such as those in electronics applications and offshore structures, where protection from impacts and/or vibrations is essential.

RSPM requires considerably less power to operate than some other earthquake-protection technologies, its developers said, in some cases necessitating only a car battery to provide enough energy to protect a 10-story building.

Because it can significantly reduce seismic responses in a structure over a broad frequency range, it also may lead to savings in construction and installation.

George C. Lee, Ph.D., Samuel P. Capen Professor of Engineering at UB and director of the National Center for Earthquake Engineering Research (NCEER), developed the system with Zhong Liang, Ph.D., research assistant professor of mechanical engineering at UB, and Mai Tong, Ph.D., a UB mathematician and NCEER research scientist.

RSPM is the first system for structures that mimics the human muscle's unmatched capacity for instantaneously contracting and releasing energy.

"The human muscle has the most efficient mechanism that we know of for absorbing energy," said Lee. "For example, if you make your way across a boat in choppy waters, you keep your balance by shifting your body back and forth and by bending your knees. You are modifying your physical parameters in real-time, adjusting your mass by tensing and relaxing your muscles at different times in order to prevent yourself from falling. Our system works the same way."

Based on a new approach rooted in the mechanics of living systems, RSPM cannot be strictly categorized as an example of a passive device, an active control system, a hybrid control system or any of the other currently accepted approaches to earthquake-protection technologies.

Instead of isolating a structure from ground motions (passive devices) or exerting a counterforce to minimize the impact of ground motions (active devices), RSPM allows a structure to adjust itself in real-time in response to an earthquake.

RSPM consists of three components: sensors, placed at certain locations in the structure; a decision-making unit consisting of a dedicated computer chip, and actuators, made of hydraulic cylinders, installed at strategic points within the walls and elsewhere.

The "brains" of the system detect the signal from the sensors and issue an order to the actuators, which then lengthen or contract to reduce the impact of vibrations on the structure.

The whole process takes hundredths of a second, said Lee.

"We have designed a system that modifies mass, damping and stiffness, the very same parameters people modify whenever they move," he said.

Just like the human body, RSPM can respond on several different levels, depending on the severity of the vibration.

"If you are reading a book and a mosquito lands on your arm, you just brush it off, without even looking up," he said. "That's a local stimulus and you respond locally. Similarly, we have developed a system that is able to respond on that level while being flexible enough to also respond to a major stimulus."

By building into it four levels of algorithms, the researchers have developed a system capable of responding to multi-directional, strong seismic ground motions.

"The technology's 'intelligence' allows it to respond to vibrations by achieving the best possible configuration for the entire structure, even when confronted with a potentially catastrophic earthquake," Lee said.

"If you feel like you are going to fall, you tense up your body and you may put your arms in front of your face," explained Lee. "You automatically assume the best posture in order to minimize damage to your body."

In the same way, he continued, the decision-making unit of the RSPM responds to severe ground motions by sending to the actuators a signal that says, in a sense, "tense up."

"It is not economical to design a structure to resist the greatest earthquake that might occur in thousands of years," said Lee, "but the fail-safe mode of RSPM allows the structure to minimize damage and avoid total collapse."

Lee emphasized the multidisciplinary approach of the research. He credited Liang with developing a key element in the system, the functional switches and a multi-function testing table, which has been used to conduct experiments with the RSPM. Tong conducted analysis of the dynamic systems in RSPM and developed the critical algorithms.

RSPM was developed out of Lee's decades-old fascination with biomechanics. In 1969, he spent a year at the Harvard Medical School where he studied respiratory physiology and the mechanics of muscle control, and began studying research developments in human physiology.

He was clearly ahead of his time.

"At that time, people did not believe in the idea," he said. "But recent developments in smart materials and intelligent structures have really proven that my idea was not just wishful thinking."