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NEES showcases pioneering approach to earthquake engineering
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The
massive Universal Testing Machine subjected a concrete column
specimen to 2 million pounds of load in an earthquake simulation
at the NEES opening.
PEG SKORPINSKI PHOTO |
Berkeley researchers have a unique role in a bold new center
funded by the National Science Foundation (NSF)—the George
E. Brown Jr. Network for Earthquake Engineering Simulation (NEES)—that
will revolutionize earthquake engineering research, improve seismic
design and performance, and may extend its reach beyond national
borders and seismic applications.
“Berkeley’s key contribution to NEES is the geographical
distributed hybrid simulation testing method,” says NEES
principal investigator Jack Moehle. “It will allow us to
shift our research emphasis from conventional physical testing
to integrated experimentation and computation, hybrid model development,
and simulation.” Moehle is CEE professor and director of
Berkeley’s Pacific Earthquake Engineering Research Center.
Officially known as nees@berkeley, the Berkeley facility
celebrated its grand opening at Richmond Field Station in November.
Under construction for four years, the center was built in an
existing lab with $5 million worth of state-of-the-art upgrades.
The preexisting strong floor and other structural components were
equipped with a reconfigurable reaction wall, new hydraulics,
new control room, and new instrumentation, including a 128-channel
high-speed data acquisition system and an array of 50 specialized
digital cameras for measuring structural deformation.
“For the first time we can make hybrid models consisting
of both physical and numerical components,” says CEE professor
Bozidar Stojadinovic, one of three principal investigators who
teamed with Moehle to build the NEES facility. “This makes
it possible to test physically the complicated parts of structures,
while the simple ones are modeled in the computer, saving money
and facilitating more tests.” Other principal investigators
are Stephen Mahin and Khalid Mosalam for construction, and Nicholas
Sitar for operations management, all on Berkeley’s CEE faculty.
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In
the NEES control room, engineer Don Clyde demonstrates how
the latest information technology helps solve the space limitations
of earthquake simulation on large and complex structures like
a suspension bridge. One lab alone cannot adequately test
such a structure, but several labs networked together can.
PEG SKORPINSKI PHOTO |
NEES will function as a shared-use collaboratory for coordinated
research, with special emphasis on six priority areas most likely
to yield major breakthroughs in earthquake engineering. These
include efforts to retrofit existing structures, mitigate soil-related
failures, develop performance-based design standards and loss
prediction models, and protect lifeline infrastructures.
The NEES labs will permit controlled simulation of complex problems
in earthquake engineering, with Berkeley providing the hybrid
testing infrastructure for the 15 sites nationwide. Such testing
can be conducted at several labs simultaneously through Internet
networking and teleobservation, facilitating sharing of resources
and interdisciplinary collaboration.
“Conventional structural design protects against collapse,
and we now do that quite well,” says Stojadinovic. “What
has been hurting us most is the economic damage after an earthquake.”
To minimize such losses, NEES researchers will develop performance-based
seismic design standards to guide building for much finer grades
of performance. Structures of the future might be designed, for
example, specifically to house expensive equipment or to fully
recover function within 24 hours of a disaster.
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