Tuscaloosa, Ala. — Engineers with NASA are using a lab at The University of Alabama to help develop a spin-off technology aimed at girding structures against earthquakes. NASA is testing what’s called a Disruptive Tuned Mass, or DTM, technology to demonstrate the new technology’s capabilities to mitigate a building’s response to earthquakes. Originally developed to solve a severe vibration issue on a rocket, NASA’s new DTM technology has potential for applications across multiple industries.
Civil structures are a natural fit. As steels get stronger and construction techniques make buildings lighter, vibration control will be needed on more buildings.
“Mitigating earthquakes in buildings is not a typical NASA mission, but the technology came from our mission. Now we want to get this out to the companies that can use this,” said Rob Berry, project manager for Disruptive Tuned Mass and Fluid Structure Coupling Technologies with NASA Marshall Space Flight Center in Huntsville.
UA was selected because of the capabilities of the Large Scale Structures Lab, opened in 2012 as part of the South Engineering Research Center. The lab is designed to study the effects of natural hazards on structures through a unique set of features inside the lab, including a seismic simulator, or shake table, and other equipment that can simulate disasters.
“There’s not another facility like this in the Southeast,” said Dr. Michael E. Kreger, director of the LSSL and the Garry Neil Drummond Endowed Chair in Civil Engineering. “The shake table fits like a glove with what NASA wants to do, and this partnership allows us to show another capability of the facility to industry and research partners in higher education.”
The DTM technology is loaded on the shake table. The high-performance, uniaxial 12-foot-by-13-foot table is designed to handle a two-story building with a maximum payload of 20 tons with a maximum acceleration of 1.2 g. Working with computers, the table can shake a structure to simulate a seismic event’s effects on a larger building.
During the April 14 demonstration, a steel-frame will be shaken with and without the technology in hopes of showing the visible difference in its ability to mitigate vibrations, Berry said.
“This facility and equipment being close to Marshall is convenient,” Berry said. “With Dr. Kreger and his partners in the lab having knowledge about earthquake mitigation made this a natural fit.”
Berry co-invented the technology with Jeff Lindner, vice president of Linc Research, for use on a launch vehicle design for NASA. Called the LOX Damper, it proved to be light and a cost-effective method of keeping the rocket from shaking beyond the bounds necessary for safe human spaceflight.
After the launch vehicle program was shuttered and NASA focused on the Space Launch System, engineers continued to mature the technology for additional applications.
Tall buildings often use systems with solid weights or shifting fluids to counteract vibrations created by earthquakes, wind or other sources by moving the mass of a building in response to vibrations. These systems are often expensive, bulky and can be difficult to retroactively install on older buildings.
The DTM technology, however, leverages existing or added mass, whether fluid or structural additions, to change the response characteristics of a building. Fluid-based DTMs can use any existing fluid mass in the building such as swimming pools, water tank, sprinkler systems, standard plumbing or existing structural mass such as air conditioning to mitigate vibrations.
The response is force independent so the same amount of reduction is achieved for daily winds, hurricane winds, 4.0 magnitude earthquake, 9.0 magnitude earthquake or any other type of loading event. Since the DTM is not a counter force or dissipation of energy approach there is no time to respond, therefore, mitigation is always present.
The DTM enables meeting design goals with a considerably smaller and cheaper system than what is currently available, Berry said. The concept has been proven to work on the tallest building at Marshall and is being used in the construction of a tower in Brooklyn, New York, but neither of those buildings have been tested with earthquake-force vibrations.
“This is a totally different way of looking at tuned mass systems,” Berry said. “It’s a lot more effective than what we’ve seen in the past, but the question to us is could it be used for earthquake mitigation. We think it can, and we have come down here to demonstrate that and test it.”