After observing the real-world effects of a moderate, late-July earthquake centered in close proximity to campus, University of California-San Diego staff are wrapping up the latest phase of large-scale specimen testing to improve design professionals’ understanding of how precast concrete structures respond to seismic forces
Sources: Precast/Prestressed Concrete Institute, Chicago; CP staff
After observing the real-world effects of a moderate, late-July earthquake centered in close proximity to campus, University of California-San Diego staff are wrapping up the latest phase of large-scale specimen testing to improve design professionals’ understanding of how precast concrete structures respond to seismic forces. Since May, researchers have subjected a three-story parking structure to various levels of seismic forces, including simulation of a Maximum Considered Earthquake level that is likely to occur only once every 2,500 years in regions of high seismic activity. Measuring 17 ft. x 58 ft., the approximately 28-ft.-tall structure features one level each of three types of flooring components: pretopped double-tees, topped double-tees, and hollow-core concrete slabs. It was erected on the world’s largest outdoor shake table, 25 ft. x 40 ft. with 2,240-ton load capacity. Testing applies ground motions at increasing levels of earthquake intensities until the highest forces are reached. Approximately 600 channels of instrumentation throughout the specimen structure provide readings for post-test evaluation. The tests build on a program PCI sponsored in conjunction with other organizations to create innovative precast structural systems equipped to preserve lives and property during a major seismic event. The latest lab work caps a five-year, $2 million-plus research program PCI initiated with an eye toward improving standards for precast diaphragms. Better design and construction methods for such components have gained priority since the 1994 Northridge earthquake in southern California.