Concrete Solutions or Lots of Controversy? : Quake-damaged parking garages rebuild with emphasis on strength. But some customers still lack confidence.

After the Northridge earthquake, images of crumpled parking garages generated horrified speculation about how many lives would have been lost had the shaking happened during a busy workday.

Eleven months later, as large garages are being rebuilt, debate continues over how best to build a quake-resistant parking garage. There is also plenty of finger-pointing over why various garages failed and criticism of certain designs and construction methods.

Those involved in building parking garages damaged by the Northridge quake argue that the building code simply didn’t anticipate how much the ground shook in the 6.7-magnitude temblor. Others blame the construction process itself, saying it encourages economy over safety. And structural engineers say that fear of crime has led to the design of large, open garages, without enough concrete shear walls to absorb shocks from a big quake.

At the Sherman Oaks Fashion Square shopping mall, the decision was quickly made by the Australian owner, City Freeholds Inc., to raze its 18-year-old, three-level, partially damaged parking garage. The company spent $6.5 million to build an all-steel, three-story garage, a type rarely found in California, where most garages are a mix of concrete and steel.

City Freeholds believes its new garage would do well in another earthquake because steel can create a very strong structure, despite a city survey that found about 100 steel-frame office buildings with severe quake damage. City Freeholds Vice President Brian Pickering noted that the Sherman Oaks mall is an all-steel construction that held up well in the quake, whereas the Bullock’s and Broadway department stores there are made primarily of concrete and suffered significant quake damage.

Another advantage of using steel is that damage is more visible and therefore can be quickly repaired, while in concrete the cracks and weak spots are harder to see, Pickering said.

The mall’s new garage was open in November, in time for the holiday shopping season and three months sooner than a concrete structure could have been finished. “We had to have the structure up for Christmas,” Pickering said.

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Despite assurances that rebuilt parking garages will be far stronger, an informal survey of shoppers last week at the new Sherman Oaks Fashion Center garage revealed that some customers are still skittish about parking there. Nancy Leonell of Encino said she doesn’t feel safer. “If it starts shaking, I’ll just run,” she said. “I hate my car, so if it gets smashed, I can collect insurance.”

Nancy Bertinelli of Studio City said she parked near the exit in case of shaking. And a mall employee who didn’t want her name used said, “I don’t think (the garage) is structurally sound.”

Mall owners admit that winning public confidence for their new garages might not be easy. When the Sherman Oaks garage opened on the day after Thanksgiving--the busiest shopping day of the year--the outside parking lot was full, but the new garage remained partially empty, Pickering said. Since then, more customers have begun parking in the garage, he said.

Meanwhile, at the Northridge Fashion Center, the most severely damaged mall in the city, all four of the parking garages were battered. One two-story garage completely caved in, another partially collapsed, and two others were badly damaged. Today, three new parking garages are going up, and the major change is that concrete will be poured in at the site, rather than having precast concrete slabs made at a factory and hauled in.

The Northridge mall’s owner, MEPC American Properties Inc. of Dallas, thinks freshly poured concrete will be sturdier. The two garages that had the worst quake damage were built in 1989 and made of precast concrete. Precast buildings can be built faster and for less, but they’ve been criticized since the quake because steel and concrete used to connect the precast segments were not strong enough in many cases and caused some garages to crumple.

In its new garages, the Northridge mall is also adding more walls to absorb earthquake shocks, as well as posts with steel cables wrapped around them to hold the concrete tightly in place. The three new garages are covered by insurance and are expected to cost about $20 million. The first garage will be finished in January, another in March and the third in June.

“We certainly may have the newest and maybe the safest decks in all of Los Angeles,” said MEPC President David Gruber. He said the new Northridge mall garages would suffer “minimal damage, if any, with the same force that hit before.”

Gruber also said his company isn’t going to sue the original contractors or structural engineers because the old Northridge parking structures were built according to the building code.

His company has organized focus group studies of local residents to find out, among other things, how they’ll feel about parking in the new Northridge Fashion Center garages. The response has been “mixed,” Gruber said.

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At Cal State Northridge, a two-story parking garage on Zelzah Avenue that caved in on one side remains a fenced-off, tangled mass of fallen concrete, perhaps the largest untouched evidence of the Northridge quake. That’s because university officials are still haggling with each other and the federal government--who will pick up most of the bill--over whether to demolish and build a new garage for about $18 million or try to repair the 3-year-old structure.

Charles Thiel, chairman of the Cal State University Seismic Review Board, said the CSUN decision might not be made for several months and it won’t be based solely on economic and technical grounds. If the people won’t park in the existing garage after repairs, he said, “I expect the university would make a decision acknowledging that” and build a new one from scratch.

Public concern might be fueled by continuing discussions over why some garages were so badly damaged in the first place.

Architect Nelson Behrend designed the third floor of the Glendale Civic Center parking garage, where some beams broke and fell through the floor during the quake. That garage has since been repaired, but Behrend said there were many results of this earthquake that “we’ve never seen before. Some of this has to do with the providence of God.”

Andy Curd, president of A.T. Curd Builders in Glendale, which built the CSUN garage that collapsed, said the structure failed because severe ground motion during the quake caused the building to bend like a tree in the wind. The motion was much greater than anticipated by the 1991 building code, he said, so columns snapped, dragging down the concrete slab, which in turn brought down part of the garage’s exterior.

Curd is now building a parking garage at County-USC Medical Center that he said would take this kind of movement into account. The biggest design change is that internal columns are being reinforced to withstand similar bending motion. The Northridge quake “is definitely changing the way things are being designed and built,” Curd said.

Some engineers say that parking garages have inherent weaknesses because ramps interrupt the interior layout and complicate the way quake forces are transferred. Robert Englekirk, the structural engineer who designed the two Northridge mall garages that suffered the most damage, noted that garages also lack ceilings, partitions and other energy-absorbing features found in houses and office buildings. “A lot of times we don’t recognize how much more movement there is in parking structures than in buildings.”

While Englekirk defended the soundness of the precast concrete method, he acknowledged that it’s been popular in part because it’s quicker to build. And even now, after the Northridge earthquake has raised concerns about parking garages, developers “want to know, is it less expensive?”

Some critics are impatient with what they see as defensiveness in the construction industry. Peter Yanev, chairman of EQE International in San Francisco, a leading earthquake engineering firm, brands as “baloney” the argument that no one anticipated the severe motion of the Northridge earthquake. His said that after the big Armenian temblor in 1988, his firm warned that precast garages should be limited or banned in seismic areas.

Experts also say it’s not the design itself that counts so much as how the design is implemented, and note that some poured-in-place concrete facilities also collapsed. One weak link in any structure could potentially cause a cave-in.

At the Northridge mall garage, for instance, the concrete shear walls that were supposed to absorb the force of the quake were the only things left standing. Instead, the force was taken by parts of the structure that weren’t meant to withstand the shaking. That means the connections between the various pieces somehow failed, said Helmut Krawinkler, director of the John A. Blume Earthquake Engineering Center at Stanford University.

“Anything that collapsed, it was almost always in the details,” Krawinkler said. Problems have surfaced with parking garages, he said, in part because they haven’t been considered as important as other buildings and are often put up as quickly and cheaply as possible. “The whole design/construction process needs better supervision.”

One result of the Northridge earthquake is that changes are expected in Los Angeles building code requirements for parking structures. Richard J. Phillips, a structural engineer who headed a city task force to study parking structures after the quake, said his group recommended five basic code changes. They include requiring more reinforcing ties to hold concrete together and other strengthening features.

The task force also advised independent reviews of engineering and construction work. Many garages are built in a process in which a general contractor is hired to oversee the entire building process. “That puts engineers in a position of a conflict of interest,” Phillips said. “There should be independent reviews to make sure the engineer is not unduly influenced by the guy who’s picking up the tab.”

Yet many warn that any building code only establishes minimum standards. Engineer Krawinkler contends that abiding by the code “is a poor defense” for anyone who designed a parking structure that collapsed in the Northridge quake.

The code is “just another silly book,” he said. “Every engineer should know that just providing the code does not make a good structure.”