UC San Diego’s huge earthquake simulator getting upgrade to better simulate deadly temblors
UC San Diego’s earthquake simulator at Scripps Ranch will soon give engineers a better sense of the fury released when quakes erupt in places around the globe from the San Fernando Valley to the mountains of Afghanistan.
The National Science Foundation recently gave the university $16.3 million to upgrade the so-called shake table so it can more accurately simulate quakes, officials said.
The outdoor table is the largest of its kind and has conducted experiments that have led to tougher building and design codes for bridges and housing. But it can only move structures backward and forward. Quakes can move the ground in many different directions.
Engineers will modify the table so that it also can move up and down, right and left, and simulate the pitch, roll and yaw that can come with ground motion, officials said. Collectively, these movements are called the “six degrees of freedom.”
The upgrade involves adding pistons and power to a table that’s used by researchers from around nation to simulate quakes big enough to send seismic waves coursing through the earth for weeks.
“We will be able to reproduce earthquake motions with the most accuracy of any shake table in the world,” said Joel Conte, the UC San Diego structural engineer who is overseeing the project.
“This will accelerate the discovery of the knowledge engineers need to build new bridges, power plants, dams, levees, telecommunication towers, wind turbines, retaining walls, tunnels, and to retrofit older structures. It will enhance the resiliency of our communities.”
The upgrade comes at a time of increased concern in California.
In June, the U.S. Geological Survey said that 38 high-rise buildings in San Francisco that were constructed between 1964 and 1994 could buckle if the city was hit by a similar 7.9-magnitude earthquake to the one that devastated it in 1906. The list includes the famed Transamerica Pyramid in the Financial District.
There’s also concern about a newer skyscraper, the 58-story Millennium Tower, which has been sinking and tilting, making it more vulnerable to big quakes.
San Diego is on shaky ground as well.
In 2017, the Earthquake Engineering Research Institute released a report that says that 2,000 people could die in San Diego if a 6.9-magnitude quake erupts on the Rose Canyon fault, which runs through the heart of the city. Potential property damage is estimated at $40 billion.
The EERI emphasized that the figures are mere estimates because modeling the complexities of earthquakes is hard to do with existing models and technology.
Even so, engineers have made progress.
Since it opened in the late 1980s, UC San Diego’s Powell Laboratories has been heavily involved in developing and testing key portions of roads and bridges, leading to changes in building codes.
The shake table was added in 2004 to give scientists and engineers better ability to test large structures, ranging from wood-frame buildings to bridge columns to a 70-foot wind turbine.
The need for such a table had been apparent for decades.
The 6.7-magnitude Northridge quake in 1994 appears to have caused the ground to move vertically as well as horizontally. That vertical movement may be the reason that some bridge support columns rose upward and pierced the decks of bridges.
Such wild ground motions weren’t unknown to engineers. The 1971 San Fernando earthquake, which measured 6.6, appears to have caused the soil to rotate in some areas. That, in turn, may have caused some buildings to turn like corkscrews.
The movement contributed to the billions of dollars in property damage inflicted by the quake.
The table has been used to relive some of these jarring events, notably the Northridge quake.
That temblor caused the thunderous collapse of a parking garage at Cal State Northridge. Engineers from the University of Arizona built a similar garage in 2008, then shook it harder than the real quake.
The experiment revealed a great deal about how such structures absorb and distribute energy, leading to a strengthening of national building codes.
More recently, a team led by UC San Diego built and tested a five-story building that had many of the features of a hospital — such as an ICU and a surgery suite — as well as a working elevator and a sprinkler system. The goal was to understand what would happen inside a hospital during a catastrophic quake.
To ensure they didn’t miss anything, engineers placed 500 sensors in and around the building and installed 70 cameras.
Then, they simulated several high-intensity earthquakes and, later, set part of the building on fire to replicate a frequent after-effect of temblors.
“What we are doing is the equivalent of giving a building an EKG,” lead engineer Tara Hutchinson later told reporters.
The experiment helped lead to the design of safer hospitals.
Today, Lindt is drawing up plans for a 10-story building that will be built on the same spot. But this time, he’ll be able to move the building in any direction he wants.
“The U.S. and California have really been at the forefront of this kind of research,” Lindt said. “The upgrade will help us keep pace with the world. We really need this.”
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