Shake, Rattle & Roll: UC San Diego Engineers Produce
Simulated Earthquake During the Great California Shakeout

Andrea Siedsma | November 17, 2008

Andreas Stavridis, a UC San Diego structural engineering doctoral student, before Thursday's earthquake test.

While residents across California prepared for the “big one” during the Great California Shakeout on Thursday, UC San Diego engineers simulated their own earthquake in order to devise better retrofit strategies for some of California’s oldest buildings.

The researchers simulated ground motions based on the 1989 Loma Prieta earthquake in California, which measured 7.1 in magnitude. During the tests, the engineers subjected a 3-story, masonry-infilled, reinforced concrete frame to a series of seismic events. The structure simulates those built in California in the 1920s and is the largest of its type ever tested on a shake table.

“There are two main objectives for this research project,” said Benson Shing, a structural engineering professor at the Jacobs School of Engineering, and the lead researcher on the project. “One is to study the performance of a large-scale structure on a shake table so that based on the failure behavior observed, we can develop effective retrofit schemes for this type of structures. The second objective is to calibrate and refine our analytical models so that we can better predict the behavior of these kind of structures in future earthquakes.”

Currently, there is a lack of reliable analysis methods to evaluate the seismic performance of these older structures and validated retrofit methods to improve their seismic behavior. In California, construction of unreinforced masonry buildings including those with brick infill walls came to a halt after the 1933 Long Beach earthquake, but many of them still exist today. Although only moderate in terms of magnitude, this earthquake caused serious damage to unreinforced masonry structures on land fill from Los Angeles south to Laguna Beach. Property damage was estimated at $40 million, and 115 people were killed.

To succeed in their goals, the UC San Diego researchers are also collaborating with a professional advisory panel, a group of practicing engineers from different parts of the country, with significant experience in the seismic retrofit of older buildings.

“This is a masonry infilled-building with clay bricks and mortar joints as partition walls,” explained Andreas Stavridis, a UC San Diego structural engineering doctoral student working on the project. “This is a typical structure representing the construction practices from the 1920s. Therefore, first, we built the concrete frame which consists of columns and beams and then the masonry panels. Due to their historical significance or economic reasons, we cannot bring them down and build new ones according to the current design practices. What we are trying to do here is to assess their seismic behavior and come up with a retrofit scheme so that we can make sure that they can withstand earthquakes.”

The ultimate goal of this $1.24 million project, funded by the National Science Foundation, is to provide methods to assess and improve the seismic performance of older buildings located in areas like downtown San Diego, Los Angeles San Francisco. The impact of this research project is vast since a large number of such structures can be found in the Pacific Northwest, and in the midwestern and eastern United States, where big earthquakes could occur even though the recurrence frequency is lower. This type of structural system is also very common in areas of high seismicity around the world, including China and the Mediterranean region.

“The brick walls in these kinds of buildings were not intended as structural elements,” Shing said. “They were intended as partition walls and also provided fire protection. When they were built, the engineers did not consider these brick walls as part of the structural system. But in reality, in a big earthquake, these walls will interact with the frame and can sometimes cause very undesirable damage.”

Stavridis inspects damage after the test.

After the structure is tested to failure this month, the researchers will use the data to validate the analytical models and analyze the failure patterns and behavior of the structure so that they can develop a scheme to retrofit a second specimen with the same design that will be built and tested in the spring 2009.

The current shake tests are being performed at the UC San Diego Englekirk Structural Engineering Center. The Englekirk Center has the largest shake table in the United States and is the only outdoor shake table in the world, allowing researchers to perform large scale tests of tall structures that can’t be done anywhere else in the world. This facility is supported by the National Science Foundation under the Network for Earthquake Engineering Simulation program.

Medical Center, Campus Leaders Hone Emergency Preparedness

Nurses triage patients during the drill.

A wave of mock earthquake victims with feigned injuries crowded the UC San Diego Medical Center in Hillcrest last week. Some pretended to have broken bones. Othersr had simulated cuts or acted out even more serious symptoms.

They were all taking part in last week’s statewide Great Southern California ShakeOut, an exercise designed to increase Californians’ awareness of emergency measures to take during an earthquake. The Medical Center opened its Incident Command Center from 10:11 a.m. Thursday when the page came in, until 3 p.m.

"UC San Diego Medical Center's response training is incredibly well organized,” said Capt. Steve Turner, from the Governor's Office of Homeland Security, who visited the hospital during the drill. “Your leadership has obviously listened to your emergency preparedness and response managers and made a serious investment in your ability to respond in a terrorist attack or natural disaster.  I have attend many, many events such as this in my 20 years in the fire service, and, from my perspective, you are very good and very fortunate."

Mock victims were triaged outside the hospital, near the Outpatient Entrance. The more serious 'injuries' were sent to one of two surge tents, where surgeons, doctors and nurses provided aid. A small tent also was devoted strictly to the management of pharmacy needs— prescription drugs— allowing the Drug Enforcement Administration to monitor the situation.

Serious injuries were taken to special tents.

Medical Center staff were not the only ones involved in Shakeout exercises. A broad range of campus leaders, including Chancellor Marye Anne Fox, gathered at the Emergency Operations Center on campus to practice the university’s emergency response in case of a large-scale earthquake. Officials discussed inspecting buildings after the tremor and evacuating staff members, faculty and students. The fault line closest to UC is the Rose Canyon fault line, which is not expected to rupture but still could cause damage, especially if the aftershocks of a major earthquake are really strong.