Pleasanton, Calif. -- A full-scale, seven-story wood-framed condominium tower not only survived a 7.5 magnitude earthquake, but it escaped with barely a scratch -- just minor drywall damage. In July, Simpson Strong-Tie participated in an unprecedented research event to highlight the importance of earthquake-resistant construction. A video documenting the project is now posted at www.strongtie.com/capstonetest.
As the world's largest full-scale earthquake test, the NEESWood Capstone project was developed to test new design methods for multistory, wood-frame buildings during large seismic events, and ultimately improve the construction and safety of wood buildings in the U.S. The project featured a seven-story, 40- by 60-ft. condominium tower with 23 one- and two-bedroom living units and two retail shops on the ground level. The condo building was subjected to simulated earthquake ground motions on Japan's E-Defense (Earth-Defense) shake table.
Project lead Colorado State University and technical collaborator Simpson Strong-Tie used the shake table to recreate a series of earthquakes based on the 1994 Northridge, California, earthquake -- a 6.7 magnitude quake. The seismic intensity on the final and strongest test on July 14 was increased to 180% of Northridge, roughly a 7.5 magnitude earthquake. Simpson Strong-Tie designed the special steel moment frames on the first floor and provided the 63 Anchor Tiedown Systems and hundreds of connectors to secure the six-story wood structure.
The research team successfully averted major structural damage to the building because it used performance-based design. Unlike traditional building design, performance-based design goes above and beyond the code minimum to increase building performance and prevent significant structural damage. Although this design method adds 5% to 15% to the upfront building cost, as the Capstone project showcased, it can save the structure and avoid millions of dollars in repairs after a major seismic event.
"We are extremely pleased with the results of the test. The performance-based design approach has been validated and shows that wood can be a great building material for mid-rise construction in high seismic regions," said Steve Pryor, S.E., International Director of Building Systems for Simpson Strong-Tie.