Don Nolan-Proxmire
Headquarters, Washington, DC                                October 3,1997
(Phone:  202/358-1983)

Jerry Berg
Marshall Space Flight Center, Huntsville, AL
(Phone:  205/544-5011)

RELEASE: 97-224

SPACE RESEARCH PROVIDES EARTHSHAKING REVELATIONS 

        Research aboard the Space Shuttle is helping to provide a
way to protect structures from major vibrations such as those produced
by severe earthquakes and high winds. 

        Dr. Mark S. Whorton, an aerospace engineer at NASA's Marshall Space
Flight Center, Huntsville, AL, has been working for several years on
resolving vibration problems in a microgravity environment that can affect
sensitive science experiments conducted aboard the Shuttle in orbit. 

        "Movements of the Shuttle, such as attitude corrections and the
activities of the crew members aboard the vehicle, create vibrations that
can affect delicate experiments being conducted on board," he said.
"Solutions to reducing these minor vibrations in space also can be applied
to reducing the effect of major vibrations produced by earthquakes and 
high winds on terrestrial structures such as buildings and bridges." 

        Whorton has been conducting his research as part of his doctoral
studies program under Dr. Anthony J. Calise in the School of Aerospace
Engineering at the Georgia Institute of Technology in Atlanta. The
research is part of a larger National Science Foundation effort to
understand dynamic loads placed on structures by earthquakes and to
identify ways of reducing their effect. The Georgia Tech research team for
the past eight years has been studying the benefits of using passive and
active control strategies to reduce the effects of earthquakes on buildings.

        "Technologies we've developed here at Marshall to protect
experiments such as those involving crystal growth aboard the Space
Shuttle are directly applicable to buildings and bridges during seismic
events. Right now we're working on developing technological 'tools' which
architects and construction engineers can use when designing more
earthquake-tolerant structures and in enabling existing structures to
better survive earthquakes," Whorton said. 

        The National Science Foundation, under its program on Earthquake
Hazards Mitigation in the Civil and Mechanical Systems Division, is funding a 
major research program on structural control.  Under this effort, the Georgia
Institute of Technology and other universities are involved in various aspects
of earthquake engineering such as developing better building materials, passive
damping methods, and active vibration control. Research activities at Marshall
are focused in the area of active vibration control.

        There are several ways to reduce the effect of structural vibrations. 
A direct approach is to stiffen the structure, which requires changing its mass
and therefore its vibration characteristics.  While this may be acceptable for
many terrestrial applications, the need for strong but lightweight structures
in space renders this option infeasible for NASA.  

        "Clearly, for applications in the space program, lightweight but
equally effective vibration-mitigating alternatives were needed.  We found
that these technologies had down-to-Earth applications as well.  One way of
countering structural vibrations caused by a strong gust of wind or seismic
ground motion is to place sensors and force producing devices called actuators
at specific locations on buildings.  As sensors in the system measure the
motion of the structure, actuators apply forces to counteract the structure's
vibrations," Whorton said. 

        "One such force device would use hydraulic pistons moving counter-
weights.  Another method involves placing adjustable tendons along the sides
of structures.  In fractions of a second, sensors in the systems can read the
structural vibration patterns caused by earthquakes or high winds and adjust
the tension on the appropriate tendons to reduce the excessive forces or
motions of the building," Whorton said. 

        All the actively controlled buildings in operation today are in Japan
with the exception of one in Taiwan.  A TV tower in Nanjing, China, also is to
be retrofitted with active vibration control.  Other new construction will
incorporate the technology, particularly in seismically active regions; and it
may be possible to retrofit the technology to other existing structures. 

        "This technology -- in part derived from the nation's space program --
is being adapted to meet the needs of the construction industry around the
globe," Whorton said.  "The active control technology for vibration isolation
is mature and is fully capable of doing the job.  This is a technology ready
now for commercial applications." 

                                -end-