Outdoor UC San Diego Shake Table Shakes Again

Article Content

This story originally appeared in the winter 2025 issue of UC San Diego Magazine as “What’s Shakin’.”

This summer, a 10-story, cold-formed, steel-framed building swayed and twisted as it underwent a simulated 6.9 magnitude earthquake modeled after the devastating 1989 Loma Prieta quake. It was one of many earthquake simulations that the building withstood during a monthlong series of tests. A few weeks later, researchers returned for fire testing. Smoke and flames fanned out the window of the building’s ninth floor to show how a building damaged by earthquakes would withstand a blaze.

It was all part of a series of tests at the UC San Diego earthquake simulator located in Scripps Ranch, just east of the Marine Corps Air Station Miramar. Funded by the National Science Foundation, the Large High Performance Outdoor Shake Table at UC San Diego’s Englekirk Structural Engineering Center is one of the three largest shake table facilities in the world and the only one located outdoors. The simulator is capable of shaking structures in six directions: back and forward; up and down; left and right; and in the three rotational movements of yaw, pitch and roll.

The outdoor location is crucial for tests like these: The UC San Diego shake table is the only place in the world where buildings more than 90 feet tall can be built and tested with simulated earthquakes. 

These tests focused on a building made of cold-formed steel — a lightweight material made from 60% to 70% recycled steel. Currently, the building codes that protect occupant safety in the U.S. limit this type of building to 65 feet tall or six stories. Researchers are asking whether the limit could be increased to 100 feet or 10 stories, even in areas with moderate to high seismic risk. And so far, test results point to yes.

“The building performed very well,” says Tara Hutchinson, project lead and professor in the Department of Structural Engineering at the Jacobs School of Engineering. “Despite 18 earthquake tests of increasing intensity, the load-bearing structural system retained its integrity.

“Cold-formed steel has a lot of wonderful benefits that will lead to resilient communities in the future,” she added. 

For example, cold-formed steel elements — studs, joists and sheets — can be assembled into modular units off-site. These units can then be assembled on a construction site to raise a building, similar to the way Lego sets are built. This technique dramatically shortens the amount of construction time on-site. 

Following the earthquake tests, Hutchinson partnered with Richard Emberley, an associate professor in mechanical engineering at California Polytechnic State University, in San Luis Obispo, to gauge how the cold-formed steel building, which had its interiors finished with drywall, would withstand controlled fires. Major fires after earthquakes have become rarer since the 1906 blaze that destroyed San Francisco after a 7.9 magnitude temblor. But earthquakes can rupture gas lines and electrical wiring, providing conditions that could ignite a fire, according to Hutchinson. That is why it is crucial to run fire tests after earthquake tests, she says.

“Seismic damage is going to create a situation where fire can spread in a building. And here we are studying how that spread from one space to another could happen, how aggressive that’s going to be,” says Hutchinson. “We don’t know what might really happen unless we perform actual earthquake tests and then fire tests following that earthquake.”

None of this would be possible without federal funding, according to the researchers. “Federal funding has supported undergraduate and graduate students in this program, in addition to supporting operations at this outdoor shake table,” says Hutchinson. “Without the NSF and this unique, large-scale outdoor shake table, researchers would have to wait for the next earthquake to occur. And we might be significantly unprepared for the next one,” says Hutchinson. 

Experiments in the shake table’s controlled environment have already led to changes in the building codes to make Americans safer during future earthquakes.