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A Bridge Too Weak? 

A UC Berkeley professor believes the unique new Bay Bridge design is fatally flawed

Wednesday, Mar 17 2004
If only Abolhassan Astaneh were a flake he could be dismissed. But as an internationally recognized authority on the design of steel structures, the UC Berkeley engineering professor and his jeremiads against one of the most expensive public works projects in Caltrans history aren't so easily ignored.

It isn't just that he considers the state's plans to replace the east span of the Bay Bridge -- with its colossal $2.9 billion price tag -- to be a boondoggle. Although that might seem reason enough to apply the brakes to a project enormously over budget and years behind schedule, especially considering that California is nearly broke, Astaneh's chief concern has little to do with dollars and cents.

Instead, the principal expert to whom Caltrans turned for advice on how to bolster Bay Area toll bridges after the 1989 Loma Prieta earthquake believes that the "signature" segment of the planned new eastern crossing between Yerba Buena Island and Oakland -- a "self-anchored" span suspended from a single, 525-foot-tall tower -- could be a catastrophe waiting to happen.

Neither he nor anyone else denies that the existing east portion, opened in 1936 and exposed as unsafe after part of the upper deck collapsed during the deadly 1989 quake, is long overdue for replacement or major retrofitting. But Astaneh argues that the novel design of the suspension section of the bridge -- to be the longest of its kind in the world and comprising roughly 14 percent of the entire new east span -- is inherently unsafe in an earthquake, sandwiched as it is between the San Andreas and Hayward faults.

While careful not to appear unconcerned about Astaneh, Caltrans officials reject his view. "We appreciate what Professor Astaneh has to say, but we don't share the same level of concern [about seismic vulnerability]," says Caltrans Chief Deputy Director Dan McElhinney, who is overseeing the new bridge project. "A good many engineers and others have looked at the design and have determined that the bridge will be safe."

Astaneh has spent the last six years telling anyone who will listen that a major quake with an epicenter near the bridge could cause the 1,850-foot-long suspension segment of the planned 1.5-mile crossing to crumble into the bay like a giant Erector set. After years of delay, work on the rest of the eastern bridge, a long causeway officially referred to as a "skyway" but derided by critics as a "freeway on stilts," began in 2002. In the last year, huge cranes hauled in to drive pilings deep into the bay's muddy bottom have become a familiar part of the landscape.

Even with the skyway construction under way, the project remains problematic. Caltrans is rudderless after Jeff Morales, an appointee of former Gov. Gray Davis and a driving force behind the bridge project, resigned as director earlier this month after three years on the job to make way for someone of Gov. Arnold Schwarzenegger's choosing.

Amid little fanfare, Caltrans in January once again pushed back the opening of bids on construction of the suspension span's tower and cables until late May. Caltrans now says it will be 2010 -- or 21 years after the Loma Prieta quake served notice about the vulnerability of the existing bridge -- before the new one is complete. Only three years ago officials were saying it would be ready by 2006 or 2007. Since then costs have soared, more than doubling original estimates. Citing the enormous challenge associated with building the one-of-a-kind suspension span, key contractors continue to balk at Caltrans' construction timetable, making Astaneh's design critique appear to be more relevant than ever.

But the professor's misgivings about the span's seismic characteristics are only part of the bad news from someone whose advice about steel bridges has long been in high demand and who was part of the research team called upon to help pinpoint the cause of the World Trade Center collapse after the Sept. 11, 2001, terrorist attacks. He insists the new bridge, too, is vulnerable to a potential terrorist bombing.

Astaneh says that a limited analysis based on computer modeling suggests that even a relatively small car bomb at the right spot could cause the entire suspension span to collapse, something that experts say is next to impossible with the Golden Gate Bridge or either of the Bay Bridge's existing spans. He says Caltrans should get independent security consultants to conduct extensive blast resistance tests, which he believes the agency has neglected to do, and determine once and for all whether the bridge will be capable of absorbing the explosion of a terrorist bomb. "It is ironic," says Astaneh, "that after all these years and so much money the new bridge in my view will be more, not less, vulnerable than the span we now have."

Caltrans' McElhinney says the matter "has been looked at by a variety of federal agencies." Caltrans, he says, is "doing all that we can to provide a structure that considers possible attacks on the bridge," including creating plans for the U.S. Coast Guard and the California Highway Patrol to monitor the span. He declines to specify what sort of blast tests may have been conducted or by whom. But Herb Rothman, the New York-based principal design engineer of the suspension segment, is less circumspect when asked if the design has been examined for vulnerability to a car bomb.

"We didn't design for blast," he says.

There is little disagreement about one thing: Building the curved suspension span is a huge challenge, requiring engineering methods never before attempted in a seismic zone.

With a typical straight-decked suspension structure, such as the Golden Gate Bridge, towers are erected first, the main cables are hung between them, and the deck is attached to the cables. That process is reversed with a self-anchored suspension bridge. Because the suspension cables are anchored in the deck, rather than in the ground at either end of the bridge, the deck must be placed high above the water on a temporary edifice known as "falsework." Then the cables attaching it to the tower are connected.

About The Author

Ron Russell


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