Abstract
THE project of building a bridge across San Francisco Bay was first discussed seventy-five years ago. Photographs of the bridge now under construction given in the Electrician of February 14 show that it is nearing completion. The twin suspension bridges are the largest in the world and are attached to hollow concrete anchorages about 280 feet above the water. The centre towers are 519 feet high and the outer ones 474 feet. The main spans of the twin suspension bridges are 2,310 feet long and the side spans 1,610 feet. A tunnel through Yerba Buena Island connects the two halves of the bridge. The eastern half of the bridge has a cantilever span 1,400 feet long which is still uncompleted. The bridge is to cost £15,500,000, and is being built for the California Toll Bridge Authority. The bridge will be lighted by the largest installation of sodium vapour lamps in the world; they are arranged along the fifteen miles of roadways for the double deck spans, the tunnel and the approaches at the San Francisco and Oakland ends. On the upper deck of the bridge, to be used for six lines of passenger vehicles and other high-speed traffic, the illumination will be specially bright. A new type of reflector is used with the lamps which does not oxidise, has a very hard surface and has a reflecting factor of more than eighty per cent. Six 1,000-watt single lens rotary beacons and five 400-watt flashing beacons will warn aircraft of the proximity of the bridge. A large number of navigational lights will be required and fog warnings will be given by five large bells and six fog sirens driven by ten horse-power motors.
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San Francisco Bay Bridge. Nature 137, 428–429 (1936). https://doi.org/10.1038/137428d0
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DOI: https://doi.org/10.1038/137428d0