Seismic code changes may open new doors for precast
New building codes being adopted across the nation will require designers in areas not typically thought of as high-seismic zones to consider more carefully how their buildings would fare in the event of an earthquake.
“The old design methods made design for seismic forces purely a function of where you were in the U.S.,” says Dale Thomas, manager, marketing and business development for the American Concrete Institute, Farmington Hills, Mich. The new guidelines require designers to take into consideration geographic location, soil conditions, and the category of use of the building, says Thomas. “A hospital, for example, has to be designed to a higher standard than a single-story office build-ing,” Thomas explains. “In places like Charlotte, N.C., for instance, a designer might have a combination of soil condition and building use that might require them to design more for a seismic event where they didn’t have to before.”
Irrespective of which of the new uniform building codes vying for adoption around the country is selected, architects and engineers will be faced with tighter parameters for seismic design, says Brian Goodmiller, national marketing director for the Chicago-based Precast/Prestressed Concrete Institute. “Geographic regions in the lowest seismic zones only had to design for wind loads,” he says. “That’s no longer the case.”
PCI is in the midst of conducting workshops nationwide to inform designers seeking options for seismic designs about the potential precast/prestressed concrete offers as a solution to their design challenges. The code changes come at a time when an industry consortium funded by the National Science Foundation and including PCI among other industry organizations is working to implement the results of the 10-year Precast Seismic Structural System (PRESSS) research program. Conducted at the University of San Diego, the program tested the performance characteristics of precast applications in high-seismic areas. A full-size structure was built on the research site to test four frame systems and one shearwall system. All reportedly performed satisfactorily.
The PRESSS program concluded in September 2001. Since then, two projects in California have been constructed using one of the systems, a hybrid moment-resistant frame technology (see BD&C, 08/01, page 32).
“Essentially, precast was not used in high seismic zones because of the jointed technology,” says Goodmiller. “Conventional wisdom said this might have been a weakness in the design. This research now reverses this thinking. Through the [PRESSS] research program, we’ve demonstrated how precast technology can perform under severe loadings.
“We’re excited,” says Goodmiller. “There’s a thirst for information with the changes in the design codes around the country.”
For more information, visit www.pci.org.