20-story earthquake-safe buildings made from wood

The researchers from a consortium of U.S. universities, with collaborators from industry and the public sector, are performing the testing at the UC San Diego shake table. It is part of the Englekirk Structural Engineering Center at the UC San Diego Jacobs School of Engineering.

Beyond safety: Designing for resiliency
Current seismic safety building codes aim to ensure human safety in large earthquakes, allowing buildings to stand long enough for occupants to leave unharmed. The building codes, however, don’t necessarily ensure that occupants will actually have a building to return to. Designing buildings that are expected to be back in service soon after a large earthquake, and with minimal repair costs, is known as designing for earthquake resiliency.

“In a large earthquake, the people inside a building may be safe, but if the building frame is crushed, they won’t have a building to return to. We want to improve on that situation,” said Pei.

Resiliency is one of the key tenants of this multi-year research project focused on tall wood buildings using mass timber materials.

“Building owners want to know, after a large earthquake, ‘How many months am I out?’” said Pei. “We want to be able to say to building owners, ‘You’ll be out for a week, and the building will likely just need repairs to a few systems that are designed to be damaged.”

The 22-foot structure being tested this week is a minimalist system aimed at collecting the information required to design tall timber buildings that have this kind of earthquake resilience.

One of the key goals is to study how the different seismic safety systems interact with each other during realistic earthquake simulations.

“We have tested the rocking walls by themselves in the lab, but as structural engineers, we know that the system is not equal to the sum of its parts. There are interactions between the parts. That’s why NHERI projects funded by the NSF are so critical. We are finally going to be able to get data on how the different components function as a system during strong earthquakes,” said Pei.

The data the researchers collect during the two-story tests will be crucial for developing the design methodology for the 10-story building.

“It’s exciting to see our earthquake shake table facility being used to design, test and validate resilient seismic safety systems made from innovative, renewable materials,” said UC San Diego structural engineering professor Joel Conte, who is the principal investigator on the NHERI NSF grant that funds the shake table operations. “Our shake table enables researchers to test structural specimens at full-scale for severe earthquake ground motions, which is crucial for making the kinds of structural engineering advances that save lives and enhance the resilience of communities after natural disasters.”

The researchers working on the two-story building will collect data through more than 300 sensor channels in three phases of testing. Data will be generated at pre-selected points to measure how the cross-laminated timber (CLT) panels bend and how the panels move relative to each other. Researchers are particularly interested in a system that allows the building to rock in response to an earthquake and on how the walls and floors interact during shaking.

In rocking wall systems, vertical, mass timber walls are connected to the foundation by post-tensioned rods that run up through the floor and special U-shaped steel energy dissipaters. The rods allow the wall to rock during an earthquake and snap back into its original upright position, minimizing the deformation and the resulting structural damage.

A consortium of universities is collaborating on this NSF project, including Colorado School of Mines, Colorado State University, University of Washington, Washington State University, Oregon State University, Lehigh University, University of Nevada Reno, and University of California San Diego.

UCSD notes that the two-story investigative testing also received support from multiple industrial partners including Katerra; Simpson Strong-Tie; Tallwood Design Institute; DR Johnson Lumber Co.; the Forest Products Laboratory; City of Springfield, Oregon; the Softwood Lumber Board; and MyTiCon Timber Connectors.