Sometime in the not-so-distant future, newly constructed buildings will be able to withstand earthquakes of the magnitude that destroyed San Francisco one century ago, scientists say.
Working with super-strong materials that can bend, stretch and compress without breaking, engineers say they are working toward the day when buildings will be able to survive earthquakes with little or no structural damage.
At Lehigh University in Bethlehem, Pennsylvania, home of one of the largest structural testing facilities in the United States, scientists have tested a next-generation “self-centering” system that uses gigantic steel bands to hold building columns and beams in place during an earthquake.
The rope-like steel bands, which are encased in plastic, are supposed to prevent a building frame from buckling during an earthquake by allowing the beams and columns to separate, rock and twist independently of one another. The system also uses friction plates that help dissipate the quake’s energy. After the tremors subside, the steel bands pull the beams and columns back to their original positions.
The system has shown promise in testing. In a hangar-sized lab just south of Bethlehem, gigantic hydraulic pistons subjected a building frame to about 50 percent more force than was generated by the 1906 San Francisco quake. Aside from some popped bolts, which engineers designed to have happen, the frame emerged unscathed.
Civil engineer James Ricles, of Lehigh’s Center for Advanced Technology for Large Structural Systems, said the self-centering system could be ready for commercial use in 10 to 15 years.
“The system allows you to minimize damage and it does it in a manner that’s very economical, using existing materials but putting them together in an innovative fashion,” Ricles said.
For most of the 20th century, preventing structural damage during earthquakes was secondary to minimizing loss of life, said Richard Sause, Ricles’s colleague and director of the Large Structural Systems center.
Now, researchers are trying to design buildings that will essentially be earthquake-proof, he said.
“We think the kind of technology that we’re developing now will allow at least modern buildings to survive (a strong earthquake) without significant damage,” Sause said.
Despite being 3,000 miles from earthquake-prone California, Lehigh is part of a consortium of 15 universities that participate in the National Science Foundation’s Network for Earthquake Engineering Simulation, a program launched in 2004 to foster research into building materials, designs and techniques that can mitigate earthquake damage.
After the unexpectedly poor performance of many steel-framed structures from the 1994 earthquake in Northridge, Calif., which killed 60 people, Lehigh engineers helped identify a popular kind of weld as the culprit, leading to improved welding techniques.
Ricles and Sause both will present papers at this week’s 100th Anniversary Earthquake Conference in San Francisco. More than 2,500 scientists, engineers, government officials and emergency response professionals are expected at the conference.
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