10-story wood building passes earthquake test
The building swayed as it would have in the 1999 Jiji earthquake in Taiwan. That magnitude 7.7 quake killed more than 2,000 people. Buildings made of steel and concrete were destroyed.
But the wood-framed high rise, built recently on UC San Diego’s Scripps Ranch shake table, showed no visible damage.
“The building is fine. We don’t need repair. Maybe we need to patch some drywall but that’s about it,” said Shiling Pei, a professor of civil engineering at Colorado School of Mines, and lead investigator for the Tallwood Project.
The Tallwood Project is a partnership between UCSD and the Colorado School of Mines, among other universities. Its test of the 10-story building is remarkable in many ways.
For one, it was the tallest full-scale building ever to be built and tested on a shake table. Secondly, it used an earthquake-safe design called “rocking walls.”
And, of course, its columns and beams are made of that sustainable resource, timber.
“Another big advantage of timber is it’s light. It’s only one fifth the weight of concrete. And it’s very forgiving. It’s like a big tree in a windstorm.” Pei said.
This building was also engineered to rock with the motion of the earth. The bottoms of the exterior walls actually rise off the ground as it rocks, secured by flexible steel cables.
“The bottom of the wall is going to uplift about an inch. A little bit less than an inch, and then on the other side,” said Joel Conte, professor of structural engineering at UCSD’s Jacobs School of Engineering.
“And this wall is pre-compressed against the foundation with these tendons. You can see two steel tendons. They’re like gigantic bungee cords,” Conte added.
California’s building code now allows buildings up to 18 stories tall to be built from what’s called mass timber. The industry needs to be convinced that timber buildings are safe and practical.
Among the many people who showed up and donned hard hats at the Tallwood Project test was a representative of the logging and wood manufacturing company Boise Cascade, which built the columns and beams for the shake-tested building.
“So putting buildings made of wood actually provides a place to store carbon. And it’s good for the environment, good for the industry, and good for you and me,” said Daniel Cheney, engineering manager with Boise Cascade.
The other earthquake simulated Tuesday was California’s Northridge Quake, 6.7 on the Richter Scale.