Devastating earthquakes often end up making buildings safer. After hospitals collapsed in southern California's 1971 Sylmar quake, for instance, the state adopted stringent new construction standards for hospitals and schools. In 1994's , buildings remained standing, but damage to equipment knocked some medical facilities out of service.
But engineers would prefer not to wait until the next disaster to put best practices to the test, which is why representatives from the National Science Foundation, the California Seismic Safety Commission, the University of California, San Diego, and a number of private companies were at a construction site on the campus of UC San Diego this week, staring up at a five-story hospital building and waiting for an earthquake to strike.
"This is the largest building ever constructed on a shake table," UC San Diego engineering professor Jose Restrepo says. Restrepo was part of the team that designed and built the university's 7.6 x 12.2–meter shakable platform more than a decade ago. Over the next two weeks, UC San Diego scientists will conduct a series of seismic tests on the life-size mock hospital; the 8.8-magnitude quake they will simulate is the same size as the one that struck Chile in 2010.
The first three floors of the buildings are covered in stucco and the top two in precast concrete, which will allow scientists to directly compare the resilience of the two building materials. An elevator specifically designed to remain functioning even in a major quake runs the height of the building. Occupying the top two floors are a mock intensive care unit and an operating room, with all equipment secured to current California seismic standards. Laboratory equipment and computer servers fill the third floor, while part of the second floor is devoted to testing earthquake safety products made by a company called QuakeHold. Inside, one flat-screen TV was mounted to the wall with the company's earthquake straps while another was left unsecured. The entire building was littered with video cameras and more than 400 sensors.
The crowd gathered around the shake table had been asked to wear hard hats and boots; some danger was assumed. As the countdown began—"Ten, nine, eight . . . "—the witnesses were silent and tense. Then, the building began a barely perceptible sway. In a little over a minute, it was over—with no visible damage to the structure.
The nonevent was exactly what the engineers had been hoping for, though they may see more action later in the month. During this week's tests, the 80-foot structure was supported by base isolators—cylindrical rubber bearings that basically act like a suspension system for a building, and add about 10 percent to the building's construction costs. "In the vertical direction, it provides strong support, but in the lateral direction it's actually quite flexible and it dissipates energy," Restrepo says. Late next week, the entire building will be lifted off the ground and the base isolators will be removed like wheels off a car. Then the building's foundation will be anchored directly to the shake table and the real quaking will begin.