Working off a $1.4 million grant from the National Science Foundation, researchers successfully completed months of seismic testing on a seven-story, wood-framed multifamily building this week near Kobe, Japan, culminating Tuesday with the biggest shake of all: subjecting the 60 foot by 40 foot, 23-unit multifamily tower—the largest to ever be tested— to a simulated 7.5 magnitude earthquake. While there was plenty of rattling and rolling captured on interior and exterior video cameras, the tower survived without a structural collapse. Although the violent shaking of tremors are viscerally charging and dangerous, resulting building collapses are by far the more deadly quake killer.
And it’s not just California that needs to take notice. In the United States, 39 states are at risk for earthquakes, say researchers for Pleasanton, Calif.-based manufacturer Simpson Strong Tie, which participated in the test in collaboration with seismologists from Colorado State University and researchers at the E-Defense shake table testing facility in Japan. “The testing thus far has shown that performance-based design for light-frame wood structures works,” says Steve Pryor, a structural engineer for Simpson Strong-Tie and project collaborator. “This will allow the engineering and building community to provide safer, better performing buildings in the most cost-effective manner."
The U.S. building industry rarely permits wood-frame buildings in excess of five stories in earthquake-prone areas. Data gathered from testing could increase the height of current wood-framed multifamily buildings as well as influence the design of future wood-frame construction. Project collaborators, including Simpson Strong-Tie and Colorado State University, will be analyzing vast amounts of data generated during three months of testing and present additional findings. “Thorough, detailed analysis of the data won’t be available for weeks, but scientists are pleased with the initial results,” says John van de Lindt, principal investigator on the test and civil engineering professor at Colorado State University.
Researchers spent the summer simulating earthquakes on the tower ranging from fairly frequent events expected every 70 years, to more powerful earthquakes that are only expected every 500 to 2,500 years, with magnitudes ranging from 6.7 to 7.5 on the Richter scale. Check out our in-depth coverage of the NEESWood Capstone construction, testing, and research effort here.