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World's Largest Earthquake Shake Table Test in Japan
A full-scale, seven-story wood-framed condominium tower not only survived a 7.5
magnitude earthquake, but it escaped with barely a scratch – just minor drywall
damage. In July, Simpson Strong-Tie participated in an unprecedented research
event to highlight the importance of earthquake-resistant construction around
the world.
As the world's largest full-scale test ever attempted, the NEESWood Capstone
project was developed to test new design methods for multistory, wood-frame
buildings during large seismic events, and ultimately improve the construction
and safety of wood buildings in the U.S. The project featured a seven-story, 40-
by 60-ft. condominium tower with 23 one- and two-bedroom living units and two
retail shops on the ground level. The condo building was subjected to Japan's
E-Defense (Earth-Defense) shake table, which simulates the ground motions of an
earthquake.
Located just north of Kobe in Miki City, Japan, the E-Defense shake table
measures approximately 65 by 49 ft. and can support building experiments
weighing up to 2.5 million pounds. The project's condominium tower weighed
nearly a million pounds and was outfitted with Simpson Strong-Tie products,
including steel special moment frames on the first floor, and 63 Anchor Tiedown
Systems (ATS) and structural connectors to secure the six-story wood structure.
Project lead Colorado State University and technical collaborator Simpson
Strong-Tie used the shake table to recreate a series of earthquakes based on the
1994 Northridge, California, earthquake – a 6.7 magnitude quake. The special
moment frame was tested to a 60% Northridge record and a 140% Northridge record.
The frames were then braced to isolate the six-story wood structure for the
remaining three tests. During the third and fourth tests, the six-story wood
building was subjected to 60% and 120%, respectively, of the Northridge quake.
The final and strongest test occurred on Tuesday, July 14. The seismic intensity
was increased to 180% of the Northridge earthquake, roughly a 7.5 magnitude
earthquake.
Initial Test Results
Remarkably, the building performed better than expected. "We saw minor drywall
cracks from window and door corners," said Steve Pryor, S.E., Simpson Strong-Tie
lead researcher for the project. "After the first four tests, the fifth and
largest test (180% Northridge) showed only a very slight increase in the amount
of drywall cracking and there was very minimal nail withdrawal. The vibrational
frequency of the building also did not change, which indicates that the
fundamental structural system in the building suffered no appreciable damage."
Unlike traditional building design, the Capstone building was built with
Performance-Based Design. This design method goes above the code minimum to help
prevent structural and nonstructural damage caused by an earthquake. The
Capstone building demonstrated that with a little more design consideration up
front and a few more dollars in construction, it is possible to save structures,
potentially saving billions of dollars after a major seismic event.
Further results of the NEESWood Capstone Tests will be presented by Steve Pryor,
S.E., of Simpson Strong-Tie and Dr. John van de Lindt of Colorado State
University, at a series of upcoming conferences, including:
Mar 1-6: 7th Conference on Urban Earthquake Engineering / 5th
International Conference on Earthquake Engineering, Tokyo, Japan
May 11-15: ASCE Structures Congress, Orlando, FL
June 20-26: World Conference on Timber Engineering, Trentino, Italy
July 24-29: 9th US National and 10th Canadian Conference on
Earthquake Engineering, Toronto, Canada
August 30-September 3: 14th European Conference on Earthquake
Engineering, Ohrid, Republic of Macedonia
September 6-8: 4th International Conference on Structural
Engineering, Mechanics and Computation, Cape Town, South Africa
Project Collaborators
The NEESWood Capstone Tests are the culmination of five universities and a
four-year $1.4 million grant from the National Science Foundation to develop a
new design approach for taller wood-frame buildings in urban, earthquake-prone
areas. Co-investigators funded by the NSF NEESWood grant include CSU, Texas A&M
University, SUNY-Buffalo, RPI and University of Delaware. Simpson Strong-Tie
served as the lead technical collaborator and provided the structural hardware
for the building. Honolulu-based Maui Homes USA was the project contractor and
was supported by the U.S. Forest Products Laboratory, FPInnovations Forintek
Division in Canada and Japan's National Institute for Earth Science and Disaster
Prevention. Additional project contributors included the Provincial Government
of British Columbia, the American Forest and Paper Association, Stanley Bostitch,
Strocal, Inc. and several other building suppliers.
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