San Francisco’s Bay Bridge is a complex steel and concrete bridge spanning  a total of 7.18 km (excluding approaches) over San Francisco Bay of the U.S. state of California.  

Includes 10 lanes (5 in each direction), pedestrians and bicycle paths. It originally carried auto mobile traffic on its upper deck, and trucks and trains on the lower, but after the closure of the Key System transit lines, the lower deck was converted to road traffic as well.

As part of Interstate 80 and the direct road route between San Francisco and Oakland, it carries approximately 240,000 vehicles per day on its two decks. It has one of the longest spans in the world.

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Construction Facts

  • The Construction began – July 9, 1933
  • The chief Engineer was Ralph Modjeski, a Polish-American.
  • Estimated Costs to be around $6.4 billion
  • It rises to 525 feet from the bay floor.
  •  The bay was 30 metres deep and the soil required a totally unique foundation-laying technique.
  • A single main suspension span some 4,100 feet (1.2 km) in length was considered but rejected. The solution was to construct a massive concrete anchorage halfway between San Francisco and the island, and to build a main suspension span on each side of this central anchorage. (See the picture above)
  • It was mainly constructed in Oakland and San Francisco with parts and work coming from all over the U.S. and the world: China, Japan, Canada and England, among others.
  •  The cantilever section was longest in the nation and third-longest in the world.
  • Much of the original eastern span is founded upon treated wood. Long wooden pilings were crafted from entire old-growth Douglas fir trees which were driven through the soft mud to the firmer bottom layers. Timberrrr !

Amazing Images from the Construction

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Article Source : Gizmodo