The Golden Gate Bridge

Golden Gate Facts & Figures
Total vehicle crossings since opening: 1,540,506,019 (as of 12/31/97)

Vehicle Crossings in 1997: 41,367,000

Vehicle Toll in May 23, 1937: 50 cents each way

Vehicle Toll Today: Free northbound, $3.00 southbound

Annual toll revenue: $58,534,000

Length of Bridge: 1.7 miles

Width of Bridge: 90 ft

Weight of Bridge: 887,000 tons

Height of tower above water: 746 ft

Height of tower above roadway: 500 ft

Load on each tower from cables: 61,500 tons

Length of one main cable: 7,650 ft

Total length of wire in one main cable: 80,000 miles

Number of wires in each cable: 27,572

Number of strands in each cable: 61

It took four years to build the Golden Gate Bridge, but today's seismic engineers estimate it could take less than sixty seconds to destroy if an earthquake's epicenter hits near the bridge. Even a weaker earthquake could cause unrecoverable damage that would close the bridge.

The integrity of the bridge is now intact, but seismic engineers believe a $175 million retrofit is required to prevent a disaster. To design the retrofit supercomputers are being used to simulate an earthquake's effect on each part of the bridge. The retrofit will take approximately five years to complete and although its cost is significant, it represents only about one-tenth of the eventual $1.4 billion replacement cost of the Golden Gate Bridge. The retrofit will help reduce the amount of violent action caused by ground motion. To achieve this, several areas will be strengthened to secure the bridge when tremors arrive. The main work will occur on the structural steel, the approach viaducts, as well the concrete piers, pylons and anchorage housings. And the main cable saddles that run to the tops of the towers will be reinforced. The steel tower shafts and the struts that connect them will be overhauled . After work is complete, engineers hope that no matter how hard the bridge is hit, it will be able to remain open to emergency vehicles and that vehicle traffic will return within a month.

For now, everything remains the same on the Golden Gate. Vehicles rush to the city and tourists walk along the railings admiring the great view. So if you're one of the lucky ones to visit the landmark, remember where to look and when to get off.


Related pages:
· Bridges
· San Francisco
· Earthquakes

Live views of the Golden Gate Bridge:

· netra.exploratorium.edu/learning_studio/CAM2/
· www.computersamerica.com/mousing_around/gatecam

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