Simulating the physical movements of earthquakes isn’t an easy task. However, shake tables provide an accurate and visually stimulating way to determine how a rumbler may affect a bridge, building or other type of infrastructure.
The University of Nevada, Reno’s earthquake simulation lab recently added a new shake table to its fleet. The new addition is the lab’s fourth shake table and can move in six directions, instead of four like the older tables. Mike Wolterbeek, a spokesman for the university, said the new table can better mimic an earthquake because it can move horizontally and vertically as well as pitch, yaw and roll rotations.
Researchers feed information into the system from real-life earthquakes in order to run the simulations. Wolterbeek said researchers take real-life information about an earthquake and run that data through the computer to create the simulation. When the new table was demonstrated, it simulated the 1994 Northridge, Calif., earthquake that measured 6.7 on the Richter scale, and 2008’s magnitude 4.7 earthquake in Mogul, Nev.
“They can take information from several different spots where it’s recorded and then they can run that recording with the computer,” he said. “It’s all computerized. Then the table will move the same motions and the same durations, and basically it’s sort of replaying the earthquake in a controlled setting.”
Photo: The shake tables can test the impacts of earthquakes on large-scale structures, like bridges. Photos by Mike Wolterbeek, University of Nevada, Reno.
Construction contractors as well as government agencies, like the California Department of Transportation and Nevada Department of Transportation, have used the shake tables to test their designs before implementing them in the real world. A future test will feature a four-span curved bridge that will be about 110 to 120 feet long and 10 feet high, Wolterbeek said, adding that it’s being built at about one-fourth the size of a real bridge.
The simulation lab also tests different materials and types of concrete to see how they would react to an earthquake. Wolterbeek said one of the current tests is a material that bends back almost to its original position after ground shaking. “What happens there is the concrete might break and it might crack, but it comes back to its original position,” he said. “It still doesn’t fall down, and it’s still possibly usable even after a big earthquake, at least for emergency vehicles and things like that.”
The shake table cost $2.5 million and received monetary support from the National Science Foundation and Federal Highway Administration.
The table is part of the College of Engineering and Department of Civil and Environmental Engineering’s Large-Scale Structures Laboratory. Wolterbeek said although the lab works with government agencies, there’s currently a waiting list because there are so many projects that participants want to test.
