TV crews film a test by UC San Diego engineering researchers Tuesday that subjected this seven-story building to mechanical shakes that duplicated the ground motions recorded during the Jan. 17, 1994, Northridge earthquake. DON BOOMER Staff Photographer Order a copy of this photo Visit our Photo Gallery

SAN DIEGO ---- Less steel may mean more earthquake safety.

Researchers at UC San Diego may have proved that point Tuesday as a giant, mechanical "shaking" table jostled a seven-story building with motions said to be identical to those recorded during the 1994 Northridge earthquake.

Walls of the concrete test structure contain half as much steel as most building codes require, researchers explained.

Too much steel can overload brittle, concrete walls and cause them to fail, they said.

Tuesday's testing showed scientists that less steel, positioned precisely, makes for buildings that can bend rather than break and better withstand earthquakes. Reduced steel and smaller foundations also mean up to 30 percent less cost for materials, they said.

"Many people don't realize that excessive building strength can actually promote poor structural performance and nonstructural damage during an earthquake," said Robert Englekirk, a co-principal investigator of the project.

The unique "shake test" at the university's Jacobs School of Engineering's Englekirk Structural Engineering Center, near Miramar, lasted about a minute.

During that minute, what researchers say is the tallest-ever concrete-and-steel test building groaned and swayed.

Safety cables tethered to the exterior squeaked and tightened as the 25- by 40-foot table shook the building up to 16 inches back and forth with movements that lasted less than one second.

The top of the 65-foot-tall building listed as computers instructed hydraulic motors to shake the $9 million table just as the shifting ground rattled another seven-story building in the San Fernando Valley in 1994, scientists said.

The building, which housed a station to measure and monitor earthquakes, was heavily damaged by the magnitude-6.7 Northridge tremor. That earthquake killed 57 people and caused an estimated $20 billion to $40 billion in damages, according to the U.S. Geological Survey.

By contrast, the windowless test building on Pomerado Road experienced only cosmetic cracks on a first-floor wall that scientists said they had anticipated.

Researchers after the test assessed the fractures and hunkered over computer monitors to examine readings taken by more than 600 sensors.

"This is all new territory for us," said Jose Restrepo, a UCSD structural engineering professor and co-principal investigator of the project. "We haven't done this test before, and there was no sign of so much as a crumb falling."

A few pieces might have fallen, Restrepo said later, but, "One small chip here or there isn't going to kill anybody," he said.

More testing is scheduled in the weeks ahead, including a simulation in early December of what Englekirk called a "granddaddy," or a severe quake that would happen once every 500 years.

"We're actually punishing this building," Englekirk told reporters. "Most buildings wouldn't begin to experience this kind of shaking."

Englekirk is the test center's founder. A separate facility at the center is designed to simulate bomb blasts.

Built in 2004, the shake table is said to be the largest in the country and the only outdoor table in the world. Because the machine is outdoors, it can test full-sized buildings.

The table can support a 2,000-ton payload. Hydraulic arms that push the platform to and fro are driven by motors that move 2,500 gallons of hydraulic fluid per minute, said engineer Larry Burman.

That kind of power can move the table ---- and a 250-ton building ---- at speeds of up to six feet per second.

According to Restrepo, building departments in Southern California have responded favorably to their findings that less steel can make for safer buildings during earthquakes.

Los Angeles has accepted plans for a 25-story building engineered by Englekirk that uses far less steel than most buildings, he said.

The engineer said that he and his colleagues plan to take their findings to Northern California.

Contact staff writer Adam Kaye at (760) 943-2312 or akaye@nctimes.com.