UCSD Researchers Sift Through Nimitz Data : Earthquake: The team that rushed to the site of the Oakland collapse will use the information to help avert similar tragedies.

By GREG JOHNSON

Oct. 26, 1989 12 AM PT

TIMES STAFF WRITER

For UC San Diego researcher Gilbert Hegemier, Oct. 17’s tragic earthquake in the San Francisco Bay Area was a raw reminder that much of what engineers know about the damage caused by temblors has been learned during field visits conducted after a quake.

“Every one of these teaches us a new lesson,” said Hegemier, who spent four days climbing over and under the collapsed section of the Nimitz Freeway in Oakland, as well as nearby structures that survived intact or suffered relatively minor damage.

Within hours of the collapse of the double-deck Nimitz, researchers from around the country assembled to measure, photograph and assess the damage. The scientists rushed to the scene because, “as (officials) tear the Nimitz down, we’re losing information,” Hegemier said. “We’re more concerned with preserving data and evidence” that will help researchers understand why the structure collapsed, he said.

The three UCSD researchers who arrived in San Francisco the day after the quake went to work even as rescuers were pulling out bodies from the Nimitz. Cars crushed by the failed structure continued to smolder, and aftershocks buffeted the bridge’s precariously balanced remains.

Because earthquake engineering is still evolving, a quake’s aftermath serves as “our main laboratory,” said Hegemier, director of the Charles Powell Structural Systems Laboratory at UCSD, where researchers test designs by subjecting buildings, bridges and other structures to earthquake-like forces.

Actual quakes provide a firsthand glimpse into why structures fail, whereas research facilities can only simulate the destructive effects.

UCSD researchers last week determined that the Nimitz collapsed when the 15-second quake shook apart the ill-designed and under-reinforced joints that connected its roadways to its massive reinforced-concrete support columns.

The joint failures were visible “in column after column after column,” according to Nigel Priestley, a UCSD structural engineering professor who has been retained by the state Department of Transportation to devise methods of strengthening suspect bridges around the state.

The massive joints, described by most experts as “state of the art” when designed during the 1950s, failed to survive the huge forces generated as the freeway lurched back and forth during the earthquake. The joints provided “a natural place for weakness, and there was virtually no reinforcement” evident in them, Priestley said.

Should Caltrans officials be held accountable for not having reinforced the joints? Probably not, Hegemier said, because joints had never before failed during an earthquake.

“This is the first time that joints have become a major concern,” he said. “It is now very clear that joints ought to be included” in Caltrans’ program to reinforce bridges.

“This is a complex and unusual bridge,” Priestley said. “It’s not a standard . . . and there are some unusual aspects to it that make it prone to damage.”

Unfortunately for those who died Oct. 17, the now-obvious design flaws became apparent only after the structure fell, Hegemier and Priestley said.

If the past is a guide, engineers will eventually craft a “Band-Aid” solution to keep the handful of bridges that share elements of the Nimitz’s design from collapsing as well.

In fact, the state has used a “Band-Aid” approach after past quakes. For example, inspections conducted after one recent earthquake alerted Caltrans to the likelihood that major quakes might destroy the circular columns that hold up as many as 700 of the state’s older bridges. Another post-quake inspection led Caltrans to reinforce certain bridges by beefing up expansion joints.

In the wake of those two quakes, Caltrans awarded UCSD a pair of contracts to find ways to buttress bridges that might not survive major temblors.

“I suppose it would be easy to extend” those contracts to include joints, Hegemier said.

But he cautioned that Caltrans should not take technology gleaned from one quake-related “fix” and attempt to use it on another problem.

Reinforcing the Nimitz Freeway’s columns wouldn’t have helped the bridge survive the Oct. 17 quake, because “this is tricky stuff,” Hegemier said. “Reinforcing one part, you may just move the failure to another part.”

The accident “could have happened anyway,” Priestley said.

“The joint problem with (the Nimitz) is not a simple one,” Hegemier said. “I could not tell you in the next five minutes how I would retrofit. The trick is to find (a solution) that’s economically feasible . . . and then you’ve got to demonstrate that it’s going to work.”

Demonstrations involve expensive, tedious work: Although the section of Nimitz was destroyed in just 15 seconds, it can take months or years for scientists to conduct an experiment that duplicates nature’s fury.

Worldwide, only a handful of facilities, including the UCSD laboratory in La Jolla, are designed to perform earthquake testing. Before construction of the UCSD facility in 1985, the only similar earthquake laboratory was in Japan. A second U.S. facility recently opened in Buffalo, N.Y.

Hegemier, whose laboratory is constantly scrambling for funding, hopes federal and state officials will respond to the worst U.S. quake since 1906 by loosening up funding for earthquake engineering research.

“There’s no doubt that, if (the country) adopts a ‘Band-Aid’ solution, that we’ll face big problems in the future,” Hegemier said. “It’s going to take both time and resources to correct the problem.”

But only full-scale testing of bridges and buildings will “uncover problems like the joints,” he said. “Otherwise you wait until the next earthquake, and that always involves loss of life and economic hardships. The more big testing we do now, the more we’ll learn.”

In the UCSD laboratory, researchers are slowly tearing apart a 60-foot span of freeway cut from an interstate bridge in the Fresno area. They also are destroying models of columns that hold up hundreds of interstate bridges.

During the 1990s, UCSD researchers will build--and slowly destroy--a five-story reinforced concrete building. The building’s carefully orchestrated death will be tracked by a complex system of sensors that will feed a constant stream of data into high-speed computers.

Researchers expect results of that experiment--along with data from other tests--to lead to improved design and construction methods that will reduce the loss of life and property during quakes.

But Hegemier, who will spend a year and $2 million to destroy the five-story building, knows that funding for earthquake research is scarce.

“We waste a lot of time trying to get funding, and once we’re up and running we seem to be renewing (that funding) every five minutes,” he said. “We have to live with that because it’s a fact of life.”

“San Francisco had a big problem, but they were lucky,” Hegemier said. “Had the epicenter been closer, the situation would have been very different. The situation demands proper resource allocations.”