San Francisco, CA
Lat: 37°48'57.74"N Lon: 122°21'10.89"W
October 17, 1989. At 5:04pm, the ground shakes from below all over the San Francisco Bay Area as a 6.9 magnitude earthquake suddenly rumbles north from the Santa Cruz Mountains. It is rush hour and commuters are heading home from work. If not for Game 3 of the World Series there would be thousands more drivers in harm’s way. As it is the Giants and the A’s are only just getting underway at Oakland Coliseum when the earthquake strikes. Everywhere in the region, building foundations and road structures give way. In Oakland, 42 people die instantly when a highway overpass pancakes, crushing them inside their cars.
The east span of the SF-Oakland Bay Bridge sways. The structure holds but the movement shifts the bridge some seven inches, causing a 50’ section of its upper roadway to shear its bolts and cantilever downward like a trapdoor, slamming onto the lower platform. Miraculously—again, probably thanks to baseball—only one driver dies in this horrific event.
That’s one evening twenty-three years ago, and the Bay Area is still in recovery-mode. Life went on, of course. The 1989 Loma Prieta Earthquake wasn’t nearly the tragedy it could have been (don’t say to the families of the 63 fatalities) but it changed life profoundly, especially for anyone who works or drives on the Bay Bridge because, eventually, that bridge—or, at least, its eastern span—would have to be entirely replaced.
Standing on the new SF-Oakland Bay Bridge is an inspiration. The new East Span now parallels its predecessor (still in use until Labor Day Weekend, 2013). It’s a stark, immediate contrast between streamlined, modern design and old, industrial functionality. When the grey, steel trusses of the original span are no longer supporting traffic they will be dismantled, dropped onto waiting barges, and shipped away for scrap, leaving the Bay Area with its newest, hippest bridge sure to rival its granddaddy to the north, the Golden Gate.
In design terms, the eastern half of the Bay Bridge is known as a Self-Anchored Suspension Span (SAS) and its most outstanding feature--among several--is the single, 525’ tower from which a mile of cable supporting the bridge is suspended. The “self-anchored” factor of the design is what separates this suspension bridge concept from more conventional ones. The Golden Gate, for example, anchors its cables in the earth at either end of the span. The SAS design is self-contained; it wraps its cable around both ends of the bridge structure and then cinches it closed. The whole span is suspended from its single, central tower and, then, in effect, anchors to itself.
I traveled aloft to the top of the SAS with its Chief Design Engineer Marwan Nader to ask him about this idea. My job gives me the awesome opportunity to meet and interview people who quickly become my heroes. But I never do quite enough research before any of my segments. This is sort of by design (I’m supposed to be discovering things in the show, so why know so much?) and sort of because I’m lazy.
But time and again, I find myself face-to-face with really smart people and I have to dive into waters far beyond my depths. Like discussing bridge design with the man who is most responsible for the new Bay Bridge. Ridiculous, when you consider it…but still fun. Watch the piece and feel for me, a man who almost flunked out of high school math talking to a man who designs world-changing bridges. Hmm.
(I would have said “world-shaking” but we’re hoping that doesn’t happen.)