NHERI TallWood Project: A historic 10-story test

We are thrilled to report on NHERI TallWood project’s record-breaking seismic test!

A global collaboration funded by the National Science Foundation (NSF), the Natural Hazards Engineering Research Infrastructure (NHERI) TallWood Project has been developing a resilient-based seismic design methodology for multi-story mass timber buildings. (We introduced the NHERI TallWood Project in the tenth edition of our biannual publication, The Connection.)

As regional leaders in both light frame and mass timber engineering, we’re so excited about this program. And we’re honored to be a part of the collaborative research team that has brought the TallWood project to life. Homed at UC San Diego, the project utilizes the world’s largest outdoor shake table. A huge project milestone, 100 of these historic earthquake simulations were conducted this past May.

Structural Project Engineer Carson Baker, who designed the structure’s concrete foundation, and assisted TallWood project team member Aleesha Busch in her research, was on the ground in San Diego to watch it happen.

Here are his takeaways:

The “Wow” Factor

“It was surreal to witness what was once only a model on my computer screen built and standing on the world’s largest outdoor shake table,” shared Carson. In total, the 10-story mass timber structure was run through 100 different earthquake simulations, and it withstood them all. A major feat for the design team!

After every batch of simulations, the on-site team would walk into the structure to check for potential damage. “It was funny because normally when an earthquake occurs, everyone’s instinct is to run out of the building. But in this case, we were eager to get back inside.”

A System Success

As a refresher, the structure’s walls were post-tensioned to the foundation and designed so that they would rock with the building during an earthquake. As the wall rocks, steel U-shaped Flexural Plates (UFPs) between the walls fold and bend with the structure to dissipate the seismic energy while keeping the rest of the building elastic. This rocking is what dissipates seismic energy and keeps a building safe during an earthquake. As an added bonus, the UFPs can be easily replaced after the earthquake, making the building seismically “good as new.” This repairability is what makes the design inherently resilient, as the building can be ready for back-to-back seismic events.

After 100 tests, the TallWood team can confidently share that the UFP system was a success! The post-tensioned, mass timber rocking walls performed exceptionally.

The Mass Timber Framework

A mass timber building of this scale had never been put through a seismic test like this. The structure itself consists of floor and wall panels made with cross-laminated timber (CLT), mass plywood panels (MPP), glulam timber (GLT), nail laminated timber (NLT), dowel laminated timber (DLT), and mass timber beams and columns. Because the structure is comprised of so many different mass timber variants, the data that was received is invaluable for the industry and future projects.

So, what happens next?

“While we’re still a way off from being able to build towers like this (due to the prescriptive building code), in the short term, we as engineers can look to these tests and use the results in our current designs because we’ve seen firsthand how these mass timber floor systems perform during a seismic event,” shares Carson.

Next phases for the TallWood Project include analyzing the gathered data, collaborating with a Japanese research team to perform additional follow-up tests, and then handing the structure over to a team at Oregon State University, who will reconfigure it into a six-story building for new testing.

As early mass timber adopters, R+D pioneers, and modern-day advocates, we are honored to have helped advance the design of mass timber buildings. 

Learn more about the TallWood project here and our industry partners here.

Cover image and video credit: University of California San Diego.