BUFFALO, N.Y. -- Unprecedented. That's how earthquake engineers
describe today's seismic test at the University at Buffalo.
Most simulated earthquake tests feature neither full-scale
structures nor ground motions in three directions, but the seismic
test of a wood-frame townhouse conducted today in UB's Structural
Engineering and Earthquake Simulation Laboratory featured both.
For 15 seconds, the two-story, wood-frame townhouse similar to
those found in southern California and constructed on the
laboratory's twin shake tables was exposed to a magnitude 6.7
earthquake like the Northridge quake that struck the Los Angeles
area in 1994. The ground motions in three directions created by the
shake tables were similar to those recorded less than four miles
from the Northridge earthquake's epicenter.
The three-bedroom, 1,800-square-foot townhouse shook violently
during the test, but did not collapse. Remote cameras located
inside various rooms showed contents falling off of desks and
shelves. Large cracks were created in the structure on each corner
of the frame above the garage door.
The townhouse is the largest wood structure in the world ever to
undergo seismic testing.
The townhouse was completely furnished for the test, down to a
car in the garage, two water heaters (one anchored, according to
earthquake protection measures and one not anchored), and dishes on
the dining room table.
An upstairs bedroom was decorated as a UB dorm room, by the
university's student chapter of the American Society for Civil
Engineers. On the wall hang T-shirts from the project's
participating universities: UB, Colorado State, Cornell, Rensselaer
Polytechnic Institute and Texas A&M.
"The goal of furnishing the house is to make the test as
realistic as possible," Andre Filiatrault, professor of civil,
structural and environmental engineering in the UB School of
Engineering and Applied Sciences and lead investigator on the UB
tests, said in an interview prior to the testing. "The test will
demonstrate in a dramatic way how much damage can occur during an
earthquake if homeowners don't take the proper precautions."
Today's test ended the first year of a four-year, $1.24 million
National Science Foundation-funded project called NEESWood,
designed to provide engineers with data on how to improve
performance of wood-frame structures during earthquakes.
Led by Colorado State University, the NEESWood research is based
on the premise that if more is known about how wood structures
react to earthquakes, then larger and taller wood structures can be
built in seismic regions worldwide, providing economic, engineering
and societal benefits.
The NEESWood project will culminate with validation of new
seismic design processes in 2009, when a six-story wood-frame
structure is tested on the world's largest shake table in Miki
While the structure previously underwent several tests of lesser
magnitude, today's shaking represented what Filiatrault said
engineers call "the 'maximum design event. It's a very realistic
test. This is a full-scale earthquake."
Constructed on twin shake tables last spring, the townhouse in
recent months has been subjected to five increasing levels of
shaking in three dimensions, the most authentic ground motions that
can be produced in a U.S. laboratory. The ground motions simulate
increasing intensities recorded during the 1994 Northridge
earthquake in the Los Angeles region.
During today's test, 250 sensors installed inside the house
gathered detailed information about how each component of the
building behaved during the simulated earthquake. A dozen video
cameras -- eight inside and four outside of the townhouse --
recorded the shaking as it happened.
According to John van de Lindt, Ph.D., associate professor of
civil engineering at Colorado State University and the lead
investigator for NEESWood, the UB benchmark testing that occurred
to today's final test already has begun to generate useful data on
how to make wood-frame homes and buildings safer for occupants
"The results from this benchmark test at UB probably will change
the way we model wood-frame structures," said van de Lindt. "That's
a huge advance because without those modeling tools, we would not
be able to achieve our greater objective, which is constructing
six-story, wood-frame structures that perform better during
earthquakes and provide an economical and sustainable construction
Detailed evaluation of the data gathered by sensors and camera
will take approximately six months to analyze, they said.
Earthquake engineers say testing like today's is long
While wood-frame construction accounts for an estimated 80-90
percent of all structures in the United States and 99 percent of
all residences in California, fewer than 10 percent of civil
engineering students are required to study wood design.
In addition to Filiatrault and van de Lindt, co-principal
investigators on NEESWood are Rachel Davidson, Ph.D., assistant
professor of civil and environmental engineering at Cornell
University; David V. Rosowsky, Ph.D., professor and head of the
department of civil engineering at Texas A&M University; and
Michael Symans, associate professor of civil and environmental
engineering at Rensselaer Polytechnic Institute.