Civil and Environmental Engineering Department personnel at the new Earthquake Engineering Lab at the University of Nevada, Reno, use a crane to reassemble one of the massive shake tables that is being moved to a more spacious location to enable tests on larger structures. Photo by Mike Wolterbeek, University of Nevada, Reno
A new facility at the University of Nevada, Reno, features four large shake tables that can test not only bridges but buildings as well.
August 12, 2014—The University of Nevada, Reno (UNR) recently opened its new Earthquake Engineering Lab (EEL) that uses equipment from its renowned Large-Scale Structures Laboratory (LSSL), which will be repurposed, greatly expanding the scope of the seismic research that the institution can conduct and host.
“The main impetus [for the EEL] was heavy demand for the existing Large-Scale Structures Lab,” said Ian Buckle, Ph.D., M.ASCE, a professor at UNR and the director of the University’s Center for Civil Engineering Earthquake Research. “The design process began with reviewing 20 years of experience with the existing lab and then deciding how to improve performance...while at the same time, making the lab more user-friendly.”
The new structure was built around four shake tables that were moved from the LSSL, with room to expand by adding a fifth, according to Buckle. The new laboratory structure was also designed to have a more versatile layout to facilitate different types of research. The limitation of the LSSL was its 150 by 50 ft footprint—a long, narrow space designed specifically for bridge related research. The new facility’s 120 by 80 ft plan and high research bay better accommodate research into the seismic performance of buildings.
In addition to the 9,600 sq ft high-bay area, the facility includes a five-story, 21,600 sq ft office block along the north side of the bay, and a 3,600 sq ft auditorium on the north side of the office block, according to Buckle, who provided written answers to questions posed by Civil Engineering online.
The new facility is a robust structure designed to accommodate the large forces generated by the four existing shake tables. “The building is a braced steel frame in one direction, and a steel moment frame in the other,” said Buckle, who noted that the greatest engineering challenge of the project was designing a foundation that was heavy and rigid enough to prevent the tables from interacting with one another during a test while still remaining affordable to build.
“The foundation under the high-bay lab is a six-cell concrete box girder on grade. At 13 ft deep, it weighs about 6,000 tons,” Buckle said. “This massive foundation is required to carry the inertia loads generated by the four shake tables without discernible movement.”
Each of those shake tables can accommodate an impressive payload of 50 tons under 1g of acceleration. Three of the tables have two degrees of freedom, while the fourth is more flexible, with six degrees of freedom—the XYZ axes as well as pitch, yaw, and roll.
Moving the shake tables was a complex operation. The team had to disassemble each of the massive machines, move the components to the new facility, and reassemble them on the robust new foundation.
By relocating the shake tables to the EEL, the university frees the LSSL for a different research purpose. “The new lab complements the existing [LSSL], which will be used to study dynamic performance of structural components that are too large for the shake tables, or for extreme loads other than earthquakes,” Buckle said.
In addition to the shake tables, the EEL features two overhead cranes with 30-ton capacity for moving test specimens around the lab, uniaxial and biaxial mass rigs to simulate inertia during tests, and a state-of-the-art network of data acquisition devices—covering 400 points in all—including video and still cameras.
Testing is already under way at the new facility. In July, a research team led by John Stanton, Ph.D., P.E., a professor in the Department of Civil and Environmental Engineering at the University of Washington, tested a new bridge bent system that can be constructed with the aid of accelerated bridge construction (ABC) techniques and also offers better seismic performance.
“There are many opportunities with a facility of this kind,” Buckle said. “For example, it will be possible to study soil-structure interaction at large-scale using a large laminar soil box mounted on the four shake tables. It was not possible to do this in the existing lab because of its narrow width, and currently this phenomenon can only be studied in soil centrifuges...and then only at a very small scale.”
The building is sited on the eastern portion of campus along Evans Avenue. UNR demolished several structures it owned on the site to make way for the approximately $20-million facility. Of that cost, $12.2 million was provided by the National Institute of Standards and Technology. The U.S. Department of Energy and UNR were also significant funders of the project. The facility is part of the George E. Brown Jr. Network for Earthquake Engineering Simulation (NEES), funded by the National Science Foundation to advance seismic research by better connecting seismic researchers around the country and around the world.