Ready to Ride Out the Big One : One Architect Sings the Praises of Springs for Quake Protection

Nobody bounced back from the Northridge earthquake faster than David Ming-Li Lowe.

*

That’s because he has springs under his house.

Seventeen truck-size coils hold up his Westside home. And Lowe credits them with cushioning it from the shaking that destroyed some nearby dwellings and businesses.

It may have been an 6.8 quake to everyone else, he says. “But it felt like a 5 in here.”

Lowe, a 61-year-old architect and professor at Los Angeles City College, installed the springs when he built his three-level home two years ago. Then he settled back and waited to test it.

“Yes, I’m probably one of the few people who was looking forward to an earthquake,” he said.

“This is the first true earthquake-resistive house in the United States. It floats--there’s no direct contact with its foundation. I’m looking to survive an 8.5 earthquake here.”

Lowe was asleep on the third floor when the Jan. 17 quake hit. He says he felt none of the violent shaking that tossed virtually everyone else in Los Angeles out of bed. “It was a very gentle rocking. I turned my fluorescent lantern on and was outside checking everything when the shaking stopped. Everything worked beautifully.”

Lowe had concocted a do-it-yourself gauge to measure his springs’ performance.

He placed rows of different-size decorative glass bricks between the concrete foundation and the bottom of the house, figuring he could tell how much the structure moved by seeing which bricks got crushed.

Shattered glass showed that the springs absorbed three-quarters of an inch of movement--mostly along the north side of the steel-framed, $800,000 residence.

While few of his Purdue Avenue neighbors may have noticed the spring system being installed when Lowe constructed his 4,500-square-foot house and a companion structure, plenty of other people did.

*

More than a dozen curious Los Angeles building inspectors trooped through to examine the “isolation bases,” as Lowe calls them. After the house was finished, it became a popular attraction for structural engineers. Eventually, the U.S. Geological Survey asked to place quake-monitoring accelerometers in it.

“My opinion is base isolators are probably a good idea,” said Jim Kaprielian, manager of the city’s West Los Angeles building and safety office and one of those who watched them being bolted in place. “Some day major structures will have them as almost a requirement. But most conventional wood-frame buildings performed well in this earthquake.”

Marvin Halling, a Caltech graduate student who is a member of the Earthquake Engineering Research Institute, agreed. He inspected Lowe’s house last week as part of the institute’s post-earthquake survey of base-isolated structures, including the Los Angeles County Fire Command facility on the Eastside and a Rockwell Corp. building in Seal Beach.

“I think it’s a neat idea. But I think a well-built wood-frame house will perform well without them,” Halling said.

“And if the springs are not properly engineered, they could amplify motions. An amateur house-builder could actually cause additional damage with them.”

USGS scientists say Lowe’s springs may have done just that.

Their accelerometer readings suggest there was more shaking inside Lowe’s house than outside. Ground movement velocity beneath the house--measured in terms of the force of gravity-- was 0.44g, according to the USGS. But readings of 0.5g and 0.63g were recorded on the first and third floors, respectively.

“It sounds to me like it didn’t work,” said Ron Porcella, a geophysicist with the USGS National Strong Motion Program.

Engineers with German-based Gerb Vibration Control Systems, Inc., dispute that, however.

*

Their company supplied Lowe with each of the $1,500 springs--which normally are used for industrial projects such as nuclear reactors. They say the coils worked perfectly.

The higher interior G-force readings were probably caused by the house bouncing onto the glass bricks, according to company President Guenter K. Hueffmann--who is coming to Los Angeles on Feb. 27 to inspect the residence.

“The system obviously did not have enough space to move,” Hueffmann said. Even so, the springs probably prevented movement from peaking at a destructive velocity of more than 1g on the third floor, he added.

Lowe plans to remove the glass bricks before the Big One strikes. In the meantime, he said he has devised a way to retrofit older houses with springs and shock absorbers that can limit both vertical and horizontal shaking.

Nobody should thump the idea of springs, he said.

At his house, they produced only good vibrations.