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 (UB) on Nov. 14, 2006, 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 it 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; however, the engineers say that damage in the test house was so extensive that in a real-world situation, repairs might total as much as the house’s original construction cost.
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 United States 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 civil, structural, and environmental engineering department 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 [completed] by structural engineers and repairs had been made."
While the researchers said that repair costs to prepare the house for occupancy 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 months.
Construction of the house was completed by Buffalo-area contractors familiar with California construction. 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 last summer and fall, and culminating with the Nov. 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.