Expanded structural engineering facilities allow innovation in seismic safety research
Earthquake engineering facility expands research capabilities with the addition of a new combined shake table and soil box system to study seismic safety of nuclear facilities and systems.
Structural and geotechnical engineers have long known that the soil underneath a building can play a critical role in the motion the building must withstand during an earthquake. For example, soft soils can significantly amplify the motion. Buildings that are unusually heavy or have deep foundations can modify the motion and affect the severity of shaking.
But this interaction between the structure and the soil is not well understood, despite its importance for key pieces of infrastructure, such as long span bridges and nuclear facilities.
Now, thanks to a $5 million grant from the Department of Energy, researchers at the University of Nevada, Reno will construct one of the world's largest soil boxes and use it to study how structures and various soils interact during an earthquake. The funding is being provided as part of a research project to examine how soil-structure interaction could impact the safety of nuclear facilities in seismic zones.
"Soil boxes mounted on shake tables are a promising way to study the response of both soils and structures during strong earthquakes, but only if the experimental errors can be minimized by working at as large a scale as possible," said Ian Buckle, civil engineering professor and project lead at the University. "This grant provides us with the exciting opportunity to push the boundaries on scale by building one of the largest boxes in the world today."
Design of soil box will require interdisciplinary expertise
Researchers will face a number of challenges in building the soil box, which will be the size of a small house and will hold as much as 500 tons of soil. Among them are developing a box that is strong enough to contain the soil during a powerful, simulated earthquakes without interfering with the its behavior. A much smaller soil box that the geotechnical faculty have already used in previous experiments has yielded promising results that may be applicable to the larger-scale box.
"This is a very challenging project, and we have put together a cross-disciplinary team of structural and geotechnical faculty who are experts in soil modeling and shake table design to tackle the problem," Buckle said. "We expect the design to take at least a year, followed by a year of fabrication and commissioning."
But Buckle and his team enjoy challenging projects and have a track record for developing innovative solutions to complex experimental projects. The Large-Scale Structures Laboratory, which is under Buckle's direction, was the first in the nation to simulate a three-span curved bridge under earthquake effects and the first to test a four-span straight bridge on its shake tables.
Larger structural engineering facilities enable new shake tables
The new shake table and soil box will be built in the Large-Scale Structures Laboratory, a facility that until last year was home to four shake tables. In 2014, those tables were relocated to the newly opened Earthquake Engineering Laboratory.
Once the system is built, researchers will embark on a three-year experimental program to study soil-structure interaction and validate computer codes for studying the safety of nuclear facilities. These codes are being developed by researchers at the University of California, Davis, and Lawrence Berkeley National Laboratory, who are collaborators in this project. The grant is being managed by the Lawrence Berkeley National Laboratory.
Once the DOE project is complete, Buckle anticipates the system will be used for studying soil-structure interaction in deep bridge foundations.
"Many long-span bridges, such as those in the San Francisco Bay Area, have massive and deep foundations in poor soil," Buckle said. "Given the current state of knowledge, engineers have little choice but to design these foundations conservatively. But conservatism comes at a cost and in this case it may be a great cost. Data from large-scale experiments in our new box could bring down the cost of long-span bridges substantially."
Earthquake Engineering at the University of Nevada, Reno
The two structural engineering laboratories at the University comprise the nation's most advanced earthquake engineering research facility. Explore our facilities in the photo galleries below and visit us at the Center for Civil Engineering and Earthquake Research to learn more about our work.