Beating earthquakes

In the future, newly constructed buildings will be able to withstand earthquakes of the magnitude that destroyed San Francisco one century ago, scientists said.

Working with materials that can bend, stretch and compress without breaking, engineers said they are working toward the day when buildings will be able to survive earthquakes with little or no structural damage.

At Lehigh University, home of one of the largest structural testing facilities in the United States, scientists have tested a next-generation "self-centring" 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-centring 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.