Repair Costs Of Seismic Test House Could Have Been Prohibitive

Newswise — 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 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 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.