Wooden framed towers could move towards earthquake proofing in two years
The world’s largest earthquake shake table test for timber-framed towers has been conducted in Japan proving that structures of seven storeys can survive high magnitude earthquakes. Tests to 7.5 on the Richter scale were conducted at the Hyogo Earthquake Engineering Research Center (nicknamed E-defense) on the world’s largest shake table at 64 x 49 ft, and found that a building comprised of a six storey timber-framed condominium block atop one story of concrete and steel (representing ground level retail) could survive intact.
“The good news is that the test was successful,” said Dr. Rosowsky, who ran the research for the Civil Engineering Department at Texas A & M University as part of a five university collaboration. “Not only did the building stay together, but it met all of the performance requirements…it met all of the drift expectations,” he told Texas University press. “This confirms that we can design and build mid-rise wood frame structures in high seismic regions and that these structures will perform satisfactorily.”
Speaking with WAN he described the advantages of advancing research in timber frames: “Wood performs very well under seismic loading. It's a ductile material and the structures are relatively lightweight. The idea here was to show that midrise timber structures could be designed and built for high seismic zones as an alternative to steel or concrete. In some cases timber may offer cost or aesthetic advantage.”
Timber has also historically proven to be a much safer material in earthquakes, its lightweight nature proving less fatal than its steel counterparts. The research conducted, known as NEESWood, is predominantly being used as a development tool for structures in the US but could help create a construction model for timber framed mid-rise towers to use in earthquake prone zones throughout the world.
The structure of the seven storey building measuring at 14,000 sq ft with 23 residential one- and two-bedroom units for living space, was designed specifically not to exceed certain inter-storey drift limits (movement between floors) which correlate strongly with damage and loss and was tested three times with simulated earthquakes ranging from 6.7 to 7.5 on the Richter scale. The ‘myriad’ of data collected from the tests is now being analyzed which could take up to two years. From this point the information can be used to refine already existing analytical models to develop new model guidelines for midrise wood structures in earthquake prone areas.
Niki May Young
(NEESWood is a collaboration between Colorado State University, University at Buffalo, University of Delaware, Texas A & M University and Rensselaer and was made possible with and a four-year $1.4 million grant from the National Science Foundation. Additional project contributors include the Provincial Government of British Columbia, the American Forest and Paper Association, Simpson Strong-tie, Stanley Bostitch and Strocal, Inc.)