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NASA’s Rocket Technology May Save You During an Earthquake
published during a waning crescent moon.
05/03/2016
Rocket Technology

This building in Concepción was destroyed during Chile’s 2010 earthquake.

The number of recorded earthquakes worldwide last month was 3,033 (and counting). These range from small tremors of 1.5 to the 7.8 quake in Muisne, Esmeraldas, Ecuador. And they happen all over the world. Anyone who lives in works in, or visits any building taller than ten stories could experience the devastating effects of this natural phenomenon. Pictures of the damage caused by earthquakes in South American and Japan once again raise the question of what can be done to help buildings withstand the earth’s shaking.

An unexpected answer is coming from an equally unexpected source – NASA. Space exploration inspires innovation, and the NASA Spinoff program actively finds ways to get those innovations into the marketplace to improve life on earth. Solving a rocket’s problems resulted in technology that can help make buildings safer.

Engineers at the Marshall Space Flight Center in Huntsville, Ala., had a rocket that shook so violently it wasn’t safe for the humans going into space. The solution they discovered to mitigate (calm) the vibrations also works on tall buildings shaken by an earthquake or high winds. To understand how this works, it’s necessary to understand what happens to a building during an earthquake.

Shimmy-shimmy-shake

All solid objects will move. The point at which they move is called their “natural frequency,” according to Rob Berry, NASA project manager at Marshall. The less a building moves, the less damage occurs. While it’s impossible to prevent a building from moving, it is possible to change when and how it moves. The usual method is adding more weight, but that’s expensive and takes up a lot of space. The weight needs to be added to the top of the building, which means only birds get to enjoy the penthouse view.

Modern construction techniques help hold a building together when it moves. Steel-reinforced concrete and more flexible building materials are two examples. Historic buildings lacking these methods fall apart a lot easier because their components are usually more rigid and brittle, and their separate parts all move in different directions. NASA discovered that changing a building’s natural frequency makes it possible to reduce shaking by more than 80 percent.

“(A) building will want to move at a certain frequency,” says Berry. “But if we can change the fundamental attributes of the building to begin with, the building itself does not want to respond.”

“We’ve tied a brick on the dog’s tail,” says Berry. “The dog wants to wag its tail. It can’t.”

When the earth moves, it creates vibrations. How much those vibrations move a building depends on its frequency. If there’s a swimming pool in that building, the water will move when the building does. That’s because the structure of the building and the water have the same frequency. But if you change the frequency of the water, it won’t move at the same frequency as the building. That makes the water, in effect, dead weight – the kind of weight helps anchor the entire building.

“We’ve tied a brick on the dog’s tail,” says Berry. “The dog wants to wag its tail. It can’t.”

The building is like the dog’s tail. It will still move a little, according to Berry, but it can’t move as much or as violently because the water (brick on the tail) is making motion much more difficult.

$5 million or $50k?

The cost to build a building or retrofit an existing building to withstand earthquakes is expensive. The price tag for skyscrapers can reach into the millions. But the NASA tech will likely cost less than $50,000.

The first version of this technology is called the Fluid Structure Coupler. It’s placed in a swimming pool or pipes filled with water, such as a sprinkler system. The Coupler is set to change the frequency of the water so that it doesn’t match the building’s natural frequency. The moment the device is installed, the building is less likely to respond to an earthquake. No special adjustments are needed.

The Coupler was successfully tested in a historic building at the Marshall Space Flight Center in Huntsville, reducing the motion by the target they set – 75 percent. That tech is now being installed in a new apartment building in Brooklyn, New York, to control motion caused by wind vibration.

Recognizing that all buildings might not have the space necessary to use the Coupler system, Berry and his team developed the new generation of this tech, the Disruptive Tuned Mass (DTM). The DTM is a hunk of steel (its weight depends on a building’s weight) installed somewhere at the top of a building, such as on the roof or under a stairwell landing. A successful test at the University of Alabama College of Engineering Large Scale Structures Laboratory (LSSL) placed the DTM atop a steel frame mounted on a “shake table.” The table simulated earthquakes of varying strengths and successfully proved that this mechanical system can help change the frequency of a building.

Old and new buildings in active earthquake zones (California, Japan, Mexico) can use either of these devices to make buildings safe, saving lives and reducing costly structural damage.

Rocket Technology

Mike Kreger (left) and Rob Berry (right) talk to media about the DTM experiment mounted on the earthquake simulator, referred to as a “􀍞shake table􀍟.”

Taxpayer tech

“The place that I think would be a radical change is if this is shown to be effective…masonry reinforced buildings that are really old,” says Michael Kreger, director of the Large-Scale Structures Laboratory in the UA College of Engineering. “They’re pretty massive, they’re stiff, but they’ not very tall.

“Part of the reason people would retrofit these types of structures (in addition) to life safety, is to protect their investment. Even if the building doesn’t collapse, you’ve got a major investment. Even if everybody in the building got out, your building may be a total loss.”

NASA hopes the private sector will get involved in creating off-the-shelf products that can be readily available to any developer or earthquake mitigation engineer.

“This technology was developed with taxpayer money,” Berry says. “The federal government holds the patents on this technology so that it’s available to everyone.”

Berry and his team are currently working on developing a third DTM technology to “expand the toolbox” to use in buildings that can’t accommodate their other devices. Stay tuned for more NASA tech improving life on Earth.

Rocket Technology

UA students watch the DTM test in the Large-Scale Structures Laboratory in the College of Engineering.