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Good Vibrations

The 1989 San Francisco Earthquake struck during the World Series, ravaged the city and severely damaged the east span of the Bay Bridge. Twenty two years later, a $5.5 billion project to make the bridge one of the most seismically advanced structures in the world is nearing completion. Here’s how they did it.

Author JACQUELINE DETWILER

SAN FRANCISCO

1 If the Big One hits San Francisco, the Bay Bridge not only has to remain standing, it has to be usable by emergency vehicles. To make this a reality, engineers designed nonessential parts of the bridge to fail during a quake, allowing the crucial elements to survive. Special pieces called shear link beams and hinge pipe beams will bend, contort and even crack when the earth moves, preserving the integrity of the rest of the structure. “It’s fuse technology,” says Bay Bridge spokesperson Bart Ney. “Like the way an electrical fuse pops to save your appliances from a power surge.”

2 The Bay Bridge is a lifeline to the city (280,000 vehicles cross it daily), so during its multiyear construction, it was closed for only three or four days at a time. The rest of the time, engineers rerouted traffic onto temporary throughways so that the bridge was continuously usable. City planners and contractors commissioned the tower and deck pieces from a factory in Shanghai, which is sending the completed parts via freighter, because it was the only company that could coordinate perfectly with their schedule.

3 California legislation mandated that the new bridge had to have “icon status” in order to fit in with the architecturally renowned neighboring bridges, including the rather fetching Golden Gate across the bay. Engineers managed to balance beauty and brawn by adding visually pleasing “wings” onto the entire span of Bay Bridge, even though they’re necessary only on the bridge’s 2,000-foot suspension section.

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