Japan’s mass‑timber use is developing in a very different way from Europe and North America, driven by unique seismic requirements that favour framed systems instead of platform systems.
That is according to Shingi Tarirah, structural coordinator for the Shinohara Group, who travelled from Japan to present at Timber Construct – Australia’s largest timber construction conference. “I thought it would be interesting to highlight some of the differences between mass timber and the rest of the world and how mass timber is manifesting in Japan,” she said.
“In Europe, North America and other places, platform construction is pretty common, so you put down a wall, you put a slab, you put another wall, and it’s kind of like a house of cards, and everyone supports everybody else.” That, however, is not the case in Japan, given its very unique seismic design codes.
As a result, Japan’s timber projects typically adopt a framed approach rather than the platform systems common overseas, Tarirah said, adding that each cross-laminated timber wall is bound by columns and beams, a choice that alters cost profiles and constructibility and demands early coordination between designers and fabricators.
“Each cross-laminated timber wall has to be framed by columns on the sides and beams at the top and bottom,” Tarirah said, requiring far more robust connections to achieve the stiffness needed for seismic loads. “You end up needing quite a serious series of diagonal screws to make sure that everyone is connected together.”
And those fastenings and connections add complexity and cost, Tarirah said, but they are necessary to meet Japan’s performance requirements. To address lateral forces on floor plates, the industry often uses composite timber‑and‑concrete systems: a concrete topping slab acts as the diaphragm to resist lateral forces while the CLT beneath supports vertical loads and improves fire performance.
“That concrete topping layer is what’s acting as a diaphragm to resolve lateral forces, and the CLT underneath, that’s just working to support the vertical loads,” Tarirah said. “So this ended up being quite a good solution for the project, because we also have to think about fire considerations, so that the concrete topping slab will protect the top layer of the timber. We also have to think about acoustic considerations. And we need at least 100 millimetres on top to get the acoustic performance.”
Travelling to Australia for the conference, Tarirah and Yuichi Shinohara, president and CEO of the Shinohara Group, said the company built two pavilions at this year’s Osaka World Expo — the Austrian and Uzbekistan pavilions — and confirmed plans to disassemble and repurpose the Uzbekistan structure.
Speaking about the Uzbekistan pavilion, Shinohara told Wood Central, “Once we’ve deconstructed everything, we’re going to put everything in the container. It’s going to be shipped back and find another life,” he said. “We think it’s going to be a library, but they’re still deciding what they’d like to do with it. And once it gets home, the Shinhara construction team are going to go to Uzbekistan and rebuild it so that it can begin its life.”
- To learn more about Shinohara’s pre-cut construction model, which could be a fix for Australia’s housing crisis, click here for Wood Central’s special feature.
