Seismic testing of NHERI TallWood Building to set a new record

The Natural Hazards Engineering Research Infrastructure (NHERI) TallWood project will investigate the resilience of tall timber buildings by simulating a series of large earthquakes on a full-scale, 10-story mass timber building this spring.

"This project is the tallest full-scale project to ever be tested on an earthquake table anywhere," said Dan Dolan, emeritus professor in the Department of Civil and Environmental Engineering who has worked on the project for almost a decade. "We want to create building designs that will have little damage in earthquakes and still be habitable."

Buildings made of mass timber — layers of wood bonded together — are gaining popularity as greener and faster alternatives to concrete and steel structures.

The research project is funded by the U.S. National Science Foundation and several other industrial organizations to determine how such buildings would fare in earthquakes. The project team designed a 10-story tall, mass timber rocking wall lateral system suitable for regions with high earthquake hazard. This new system is aimed at resilient performance, which means the building will have minimal damage from design level earthquakes and be quickly repairable after rare earthquakes.

"Mass timber is part of a massive trend in architecture and construction, but the seismic performance of tall buildings made with these new systems is not as well-understood as other existing building systems," said Shiling Pei, principal investigator and associate professor of civil and environmental engineering at Colorado School of Mines who is leading the project. "The rocking wall system basically consists of a solid wood wall panel anchored to the ground using steel cables or rods with large tension forces in them. When exposed to lateral forces, the wood wall panels will rock back and forth — which reduces earthquake impacts — and then the steel rods will pull the building back to plumb once the earthquake passes."

Due to this seismic movement induced by the rocking system, building components, such as the exterior facade, interior walls and stairways, are in for a big ride.

"Resilient design must also account for the building's nonstructural systems, which are not part of the structural load-resisting system, but play an important role in the building's function and its ability to recover after the earthquake," said Keri Ryan, a project co-investigator and engineering professor at the University of Nevada, Reno.

The tests are scheduled to start this month at the University of California San Diego outdoor shake table — one of the two biggest earthquake simulators in the world. Located at the Englekirk Structural Engineering Center at the University of California San Diego, the facility is part of the NSF's Natural Hazards Engineering Research Infrastructure. The shake table has the largest payload capacity in the world. It is capable of carrying and shaking structures weighing up to 2000 metric tons, or 4.5 million pounds.

Tests will simulate earthquake motions recorded during prior earthquakes covering a range of earthquake magnitudes on the Richter scale, from magnitude 4 to magnitude 8. This will be done by accelerating the table to at least 1g, which could accelerate the top of the building to as much as 3gs. For reference, fighter pilots experience up to 9gs of acceleration in flight.

In 2017, the project team carried out a test on a two-story mass timber building by simulating shaking from the Northridge Earthquake, a magnitude 6.7 earthquake that struck Los Angeles in 1994. The building was subjected to 13 earthquake tests and remained structurally damage-free. In addition to demonstrating that mass timber building systems can be seismically resilient, those tests helped the research team develop the design and analysis methods that have been used for the 10-story building.

The information from the testing will be used to develop design guidelines for such rocking structures in wood buildings, which will make them easier and more economical to build, said Dolan. He chairs a subcommittee on the Building Seismic Safety Council that is working to develop the guidelines for all types of rocking structures.

The project is supported by the National Science Foundation. A consortium of universities are collaborating through NSF support on the NHERI TallWood project, including Colorado School of Mines (lead), University of Nevada, Reno, Colorado State University, University of Washington, Washington State University, University of California San Diego, Oregon State University, and Lehigh University. The project also received support from U.S. Forest Service, Forest Products Laboratory, and a number of industrial partners. The NHERI shake table facility operates through NSF support under cooperative agreement 2227407 and was recently upgraded under cooperative agreement 1840870.