Shock absorbers for woodhouses
In November 2006, a 73,000-pound, 1,800-square-foot woodhouse will be subjected to the equivalent of a very powerful earthquake... in a lab. This house will be equipped with shock absorbers installed horizontally throughout its walls. The experiment will be recorded with the help of 250 sensors installed throughout the house and of a dozen video cameras. Even if the house is expected to be severely damaged, this will help structural engineers to "safely increase the height of woodframe buildings in active seismic zones." This also might save some lives -- if such dampers become commonplace. But read more...
This experiment, called NEESWood, involves researchers at several universities and institutions. Here is what says one of them, the Rensselaer Polytechnic Institute (RPI), about building woodframe houses in active seismic areas.
The height of woodframe buildings traditionally has been limited to about four stories, mainly due to a lack of understanding of how taller structures might respond to earthquakes and other natural disasters. "We don't have accurate physical data to fully define how wood structures behave in earthquakes," said Michael Symans, associate professor of civil and environmental engineering at Rensselaer.
This is why the researchers decided to run an experiment on a real house. And the tests will be done at the University at Buffalo's Structural Engineering and Earthquake Simulation Laboratory (SEESL), which has two large shake tables.
Below is one of these huge platforms (Credit: NEESWood project).
But how can you integrate shock absorbers into a house?
The damping system is essentially made up of fluid-filled shock absorbers installed horizontally throughout the walls of the house. "If we can channel some of the energy into the dampers, we can reduce the strain energy demand and thus reduce damage to the structure," Symans said. The damping technology has been applied to steel and concrete buildings, but never before to wood structures.
Previous large-scale shake table tests have been performed on simple, box-like structures, but the NEESWood Project involves testing of a much more realistic building, Symans said. The townhouse in this experiment has balconies, an atrium, and other defining features that are more likely to be in the floor plan of a real woodframe residential building.
Here is what this house looks like (Credit: NEESWood project).
If you want to see how the house was built inside the lab structure, here is a link to a short but funny video (Windows Media Player format, 1'47", 3.43 MB).
For more information, you can read "Lights, Cameras, Quake: Wood Townhouse to Undergo Seismic Testing," a University of Buffalo news release which states that "the full-scale townhouse will be subjected to the most violent shaking possible in a laboratory -- mimicking what an earthquake that occurs only once every 2,500 years would generate." As if an earthquake could happen with the same strength every 2,500 years...
You also can check the NEESWood homepage at Buffalo which describes the various phases of the project and contains more references.
Sources: Rensselaer Polytechnic Institute news release, via EurekAlert!, June 20, 2006; and various web sites
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