Tuesday, April 17, 2012
SAN DIEGO Unlike real earthquakes, this one came with a two-minute warning and a countdown.
The shaking table began moaning as the machine reproduced an 8.8 magnitude quake, like the one that ravaged Chile. Moving a fully equipped five story building that weighs millions of pounds is no small feat.
Engineers can reproduce the force and impact of a killer earthquake on simulations run by computers. For months, they have been building this structure on a shaking table, because computer simulations don't compare to shaking a building in real life.
"It's like going through a car crash where the building may be OK with some kind of little dimples and scratches there," said Jose Restrepo, a UC San Diego engineer. "But the contents will experience more damage. And that's what we're trying to study for the future. "
Researchers hope the tests tell them how pipes, stairwells, elevators and other non-structural components perform under severe stress. The research is unique because it is being done on a complete building, with all the elements of a real five story structure.
"And then you see the five stories, on the roof you see a water tank. You see a little mezzanine there," said Joel Conte, a UC San Diego structural engineer.
Conte points at the stucco covered structure. Inside there's a simulated hospital surgery suite, an intensive care unit and a computer server room. All experienced quite a ride.
"When we simulated some earthquakes under the building, I saw the base isolators deforming a lot," Conte said. "And the building moving as a rigid box, very slowly back and forth. With no distortion. No damage."
Seventy cameras and more than 500 sensors will tell researchers the story of the test, but it will take months to to interpret the results. The building will be shaken again several times without the base isolators, and those results will be compared to these tests. Next month the scientists will also light a fire on the third floor to see how that affects the structure.