Tall wood isn’t new. The pagodas of Asia were the skyscrapers of their day: China’s Wooden Pagoda of Yingxian, built in 1056, tops out at about 67 meters (220 feet).
But the lumber used in multi-story buildings today differ greatly from the two-by-fours that frame the typical single-family home. Beams, floor panels, and wall sections are made of multiple pieces of wood laminated together, often with different layers arranged at right angles to each other. The pieces can be fastened together with ordinary screws or nails, or joined by steel plates.
The result is a material that’s high-strength but far lighter than steel or reinforced concrete. And while fire has historically been a concern for wooden structures, Francisco said the thicker the material, the harder it is to burn.
“We know if done properly, it’s very fire-resistant and very safe,” he said. “We just have to learn how to do that in today’s context.”
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And speaking of those ancient temples, they’ve withstood untold numbers of earthquakes over the centuries. That’s in part because wood’s flexibility helps them stand up to seismic shaking, said Shiling Pei, a civil engineer and assistant professor at the Colorado School of Mines near Denver.
“There’s other people arguing the life-cycle benefits and carbon sequestration,” Pei said. “But structurally, wood especially for seismic issues is light and naturally very resilient. It immediately cuts down your design demand compared to a concrete-and-steel building.”
Pei and his colleagues are preparing to test a two-story structure built from modern timber construction on a “shake table” at the University of California, San Diego as part of a National Science Foundation-backed effort to test wooden construction. He said earthquake-prone Japan has tested structures up to six stories and found only minor damage. And when there is damage, wooden buildings are faster and easier to repair, he said.
“What we’re hoping is with the research and large-scale testing, the engineering community can gain confidence and this can become a common practice.”