BUFFALO, N.Y. -- While the group of 200-plus faculty, students
and media spectators who gathered at the Structural Engineering and
Earthquake Simulation Laboratory (SEESL) at the University at
Buffalo on Nov. 14 to watch the world's largest seismic test on a
wooden structure probably came away feeling that the house held up
very well, a close survey of the damage told a different story.
According to the structural engineers at UB and other
institutions who conducted the testing, had this been a real
earthquake, the damage sustained by the house would have rendered
it uninhabitable and in need of major repairs.
Final data analysis will take several months, but, the engineers
say, damage in the test house was so extensive that in a real-world
situation, repairs might total as much as the house's original
The test, a simulation of the 1994 magnitude 6.7 Northridge
earthquake, was part of a four-year, $1.24 million international
project called NEESWood, funded by the National Science
Foundation's George E. Brown Jr. Network for Earthquake Engineering
Simulation (NEES). The 80,000-pound, two-story house was
constructed on top of twin, movable shake tables in UB's SEESL, the
only laboratory in the U.S. large enough and sophisticated enough
to conduct the test.
"In a real earthquake, this house would have been 'yellow
tagged,'" stated Andre Filiatrault, Ph.D., UB professor in the
Department of Civil, Structural and Environmental Engineering and
the lead UB investigator on the NEESWood project. "That means that
the owners would have been allowed to go into the house for a brief
time to gather some belongings. They would then not be allowed in
again until a detailed investigation could be made by structural
engineers and repairs had been made."
During the final test, Filiatrault explained, the top of the
wall containing the large garage opening underwent a maximum
displacement of nearly four inches relative to its base.
"That's about double the expected displacement in a design level
earthquake," he said.
The second level of the building experienced a peak acceleration
of over 1.5 times gravity, which means that a person standing in
one of the second floor bedrooms would have been subjected to a
lateral force equivalent to 1.5 times his or her body weight.
"It would have been very difficult to remain standing under such
a force," said Filiatrault.
As a result of these high lateral forces, he said, a whole
section of the gypsum ceiling failed on the second floor.
Significant uplift and rocking of the foundation were observed
in the transverse (short) direction of the building during the
This caused the entire foundation wood sill plate all around the
perimeter of the building to split and crack.
"Replacement of this sill plate, which would require jacking the
entire building, would have been very expensive for the owners,"
The test also left the first level of the house as a whole
leaning forward on its foundation by about half an inch, enough to
pose a potential safety hazard to occupants in the event of
aftershocks, he said.
All over the inside of the building, severe cracking of the
gypsum wallboard was observed, another significant repair cost;
some wood studs in the garage also were damaged.
While the researchers said that repair costs to get the house
ready for occupancy again would vary by region, they also said that
it would probably equal a substantial amount, perhaps as much as
the original construction cost of the building.
"And that doesn't include the costs associated with the
replacement of the contents of the building that were severely
damaged during this extreme shaking event," added Filiatrault.
The researchers' analysis of data from the 250 sensors installed
inside the house and a dozen video cameras stationed inside and
outside the house during the test should be complete in about six
Demolition of the 1,800-square-foot house took place earlier
this month over the course of five days. A time-lapse video of the
demolition to the tune of the Nutcracker Suite may be viewed at http://nees.buffalo.edu/projects/NEESWood/video.asp.
Construction of the house was done by Buffalo area contractors
familiar with California construction (see http://www.engr.colostate.edu/NEESWood/sponsors.htm).
The seismic tests were conducted by a dedicated group of UB
faculty, staff and students with important contributions from
colleagues at the other NEESWood institutions, including Colorado
State University, Cornell University, Texas A&M University and
Rensselaer Polytechnic Institute.
Led by John van de Lindt, Ph.D., associate professor of civil
engineering at 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.
Conducted during last summer and the fall, and culminating with
the November 14 event, the UB tests were the first step in moving
toward performance-based design for wood frame structures. NEESWood
will culminate with the validation of new design processes using a
six-story wood frame structure that will be tested on the world's
largest shake table in Miki City, Japan, early in 2009.
The University at Buffalo is a premier research-intensive
public university, the largest and most comprehensive campus in the
State University of New York.