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THINKING BIG : Engineers : Bridging the Gap Between Vision and Reality : As a boy, Chuck Seim was awe-struck by San Francisco's Golden Gate. Today, his firm is helping to prepare the span for the 'Big One.'

May 30, 1995|MARTHA GROVES | TIMES STAFF WRITER

SAN FRANCISCO — Naysayers wailed that it couldn't be built.

Yet in May, 1937, 200,000 Depression-weary revelers helped San Francisco christen its Golden Gate Bridge--a majestic, orange-vermilion miracle spanning a mile-wide cleft in the Northern California coastline. Joseph B. Strauss, the wisp-like engineer credited with prodding the project to completion against seemingly insurmountable odds, celebrated the feat by penning poetry.

In South-Central Los Angeles, the young son of a laborer pored over magazine and newspaper reports about the bridge's scope: the unheard-of 4,200-foot-long main span, the unfathomable weight of 726 million pounds, the 80,000 miles of wire bundled into twin cables sweeping up and over two Art Deco towers 746 feet high.

"I marveled at how engineers could build such tremendous structures," said Charles (Chuck) Seim, the awe-struck laborer's son, now 70 and an engineer himself. To this day, he added, he cannot drive across or look at the Golden Gate Bridge without feeling a sense of thrill and wonder.

Now Seim is bringing that emotional connection and his engineering expertise to bear in helping direct his firm on a $170-million plan to make the famous suspension bridge capable of surviving the "Big One," and his thoughts on the great span give a glimpse into the engineering mind. It's far more than computers and blueprints.

Tough as building the Golden Gate Bridge was, Seim said, the seismic retrofitting promises to be even more of a challenge--but one that, despite his age, he is tackling with the enthusiasm of a boy at a big ballgame.

"We have to work within the bounds of the structure," he said. "We can't alter it."

When the Loma Prieta earthquake struck in October, 1989, the Golden Gate Bridge suffered no significant damage, thanks to a fundamentally sound design, devoted maintenance, interim improvements to both approaches--and no small amount of luck. Its brawny neighbor--the San Francisco-Oakland Bay Bridge, situated on less firm ground--suffered the collapse of a section of its upper deck and was closed for a month of repairs.

On a recent afternoon on the Golden Gate Bridge, a brisk wind blowing and the cold fog chilling to the bone, the rangy and mustachioed Seim thought about the Big One.

Had the 7.1-magnitude Loma Prieta quake been centered closer to the Golden Gate Bridge--say, seven miles west on the San Andreas Fault rather than 60 miles south in the remote Santa Cruz Mountains--severe damage almost certainly would have resulted, the engineer said.

Up the ante to an 8.3-magnitude quake, the size of the 1906 calamity that made the words San Francisco and quake synonymous, and the bridge would be at risk of collapsing, Seim said.

"While it took only four years to build the bridge, it could take less than 60 seconds to destroy it," agreed a report from the Golden Gate Bridge, Highway and Transportation District, which owns and operates the span.

Immediately after the 1989 quake, the district asked T.Y. Lin International, a San Francisco engineering firm where Seim is a senior principal, to determine the bridge's vulnerability. A second study by the company explored measures that could be taken to retrofit the structure to meet criteria developed by a state board of inquiry in the aftermath of Loma Prieta.

Retrofitting of vital transportation links such as the Golden Gate Bridge, the board determined, must ensure not only against collapse but also against severe damage that would render the bridge unusable to emergency vehicles. Another object is to make sure that the bridge could be made available to regular traffic soon after a big quake.

Under current plans, as part of the multifaceted retrofit, pylons will be strengthened with steel plates, rivets in the towers will be replaced with bolts, and the northern and southern housings for the cables will be bolstered with internal shear walls.

Hanging over the effort--which has stalled because of a lack of federal funding--is the ever-present threat that the Big One could occur at any moment.

"We feel that we're competing against time, but it's not a headlong race like an asteroid that's due to smack into Earth in two years," Seim said. "We are not shortchanging the retrofit to save time; if anything, we're taking extra time."

Indeed, modern engineering has become very much a team effort, Seim said. Gone are the days of great engineers handling big projects on their own.

"Engineering technology today is so complex--it embraces the full spectrum of technologies that feed in," Seim said.

On this project, as many as 50 engineers and other specialists have been involved at one time or another, assessing everything from ground motion to historical merit. (Historical architects were enlisted to offer guidance on aesthetics and heritage.)

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