Coatings Industry News

Main News Page


All Shook Up: Quake Safety Slides Ahead

Monday, November 24, 2014

Comment | More

Tomorrow's homes may be shaken, but not stirred, by major earthquakes if structural research now underway in California remains successful.

A team of Stanford University engineers says it has designed, constructed and tested a house that can withstand a quake three times as powerful as the destructive 1989 Loma Prieta temblor.

test house
Screen grab via YouTube / Stanford University

Engineers have built and tested a three-bedroom house that can survive major California quakes.

That 6.9 magnitude quake killed 63 people and caused the catastrophic failure of several major transportation structures, including a span of the San Francisco-Oakland Bay Bridge and the double-deck Nimitz Freeway.

The Toll on Homes

“Residential homes already do a good job of keeping the people inside safe when a temblor hits,” according to the university. However, seismic activity typically causes a lot of minor structural damage.

For example, after the 1994 Northridge quake, most of the $25.6 billion repair tab was spent on fixes to 500,000 residential structures, the university noted.

Even if the walls of a home stay up in a quake, interior drywall and stucco, as well as cabinetry and other architectural fixtures are often damaged because of the violent sideways movements, Deierlein said.

Seismic Isolation

The research team's test house features several inexpensive design modifications, including reinforced walls and sliding isolators that allow the structure to skate along the shaking ground instead of collapsing, project leader Gregory Deierlein said in a research announcement. Deierlein is Stanford’s John A. Blume Professor in the School of Engineering.

NimitzFreewayCollapse
U.S. Geological Survey

The 1989 Loma Prieta earthquake collapsed a section of the double-deck Nimitz Freeway. Researchers say their test house can withstand a shock three times that of Loma Prieta.

These modifications could be incorporated into new homes as soon as designers and builders decide to use them, the team says. The technology may also lead to building code changes.

In lieu of a conventional foundation, the new structure rests on a dozen steel and plastic sliders that measure 4.5 inches in diameter, according the announcement.

Under the sliders are plates or bowl-shaped dishes made of galvanized steel. The dishes are known as “seismic isolators.”

“The idea of seismic isolation is to isolate the house from the vibration of the ground,” said Eduardo Miranda, an associate professor of civil and environmental engineering. “When the ground is moving, the house will just slide.”

Similar units are already in play, protecting large structures like San Francisco City Hall and structures at San Francisco International Airport, but they are expensive, Deierlein said.

His team adapted the technology for residential use by incorporating inexpensive materials into the scaled-down isolators.

Sturdy Walls

The home also features a “unibody design,” a term borrowed from the automobile industry, in which every element of the structure contributes to its strength, according to the university.

Unlike typical construction, where drywall is screwed into the wood framing, the team used glue to affix 5/8-inch-thick drywall more securely to the framing.

On the exterior, they used strong mesh and additional screws to attach the white stucco tightly, the team noted.

These elements reportedly made the house stiffer and stronger, leading to a significantly better seismic performance.

Testing

The team tested the three-bedroom house using the largest earthquake simulator in the country: the Large High Performance Outdoor Shake Table at the University of California, San Diego.

The facility uses computer-controlled hydraulic pistons to move the platform back and forth in a pattern selected by the engineers, so it can mimic specific earthquakes like the Loma Prieta.

It took the team seven weeks to build the boxy test structure. Testing was executed in September.

usgs
USGS

The team developed the home 25 years after Loma Prieta, which hit Oct. 17, 1989, in the San Francisco and Monterey Bay Regions.

The engineers shook the table at three times the intensity of the ground shaking during Loma Prieta, which struck the San Francisco and Monterey Bay regions on Oct. 17, 1989.

The house slid from side to side atop the sliders during testing but remained intact, the researchers reported.

“Under the isolators, the house basically saw no damage,” Deierlein said.

The team also bolted the home to the shake table to test the unibody design system separately. They developed computer models to predict when the house would fall, but it outperformed their expectations, the team says.

Under the triple-Loma Prieta conditions, a few cracks appeared in the stucco and drywall, and a swinging light in the garage shattered. The test window and steel door stayed put, as did the table and chair that furnished the test house, the university related.

Cost of Modifying

Deierlein estimates that the isolators would run up the cost of a 1,500- to 2,000-square-foot house by $10,000 to $15,000. Contractors could install them in about four days before building the home on top, he said.

The unibody method would add a few thousand dollars to the cost of building a home the size of the test home, Miranda said.

Both technologies could also be used to retrofit existing homes but would be much easier to incorporate in new construction, the report related.

"We are always cautious never to talk about earthquake-proof," Deierlein said, "but our resistance is getting better and better."

   

Tagged categories: Architecture; Building design; Design; Disasters; Engineers; Health & Safety; Health and safety; Infrastructure; Maintenance programs; North America

Comment Join the Conversation:

Sign in to our community to add your comments.


Advertisements
 
SAFE Systems, Inc.

 
Modern Safety Techniques

 
ABKaelin, LLC

 
Sidewinder/Persyst Enterprises, Inc.

 
Tarps manufacturing, Inc.

 
Sauereisen, Inc.

 
Fischer Technology Inc.

 
DeFelsko Corporation

 
KTA-Tator, Inc. - Corporate Office

 
Mitsubishi Gas Chemical America

 
 
 

Technology Publishing Co., 1501 Reedsdale Street, Suite 2008, Pittsburgh, PA 15233

TEL 1-412-431-8300  • FAX  1-412-431-5428  •  EMAIL webmaster@paintsquare.com


The Technology Publishing Network

PaintSquare the Journal of Protective Coatings & Linings Paint BidTracker

 
EXPLORE:      JPCL   |   PaintSquare News   |   Interact   |   Buying Guides   |   Webinars   |   Resources   |   Classifieds
REGISTER AND SUBSCRIBE:      Free PaintSquare Registration   |   Subscribe to JPCL   |   Subscribe to PaintSquare News
MORE:      About PaintSquare.com   |   Privacy Policy   |   Terms & Conditions   |   Support   |   Site Map   |   Search   |   Contact Us