Just six months prior to the inauguration of the more popular Golden Gate Bridge, the San Francisco-Oakland Bay Bridge or simply Bay Bridge was finished in 1936. The bi-level bridge spans 7 kilometers and joins San Francisco with Oakland across the San Francisco Bay.
Plans of building a connecting infrastructure between San Francisco and Oakland that would traverse the San Francisco Bay has been conceptualized as early as the 19th century. However, the numerous engineering difficulties and technical challenges, coupled with the high cost of building a bridge of such kind relegated these plans to the backseat.
Construction of the Bay Bridge eventually commenced on July 9, 1933. The bridge was finished in phenomenal pace, just three and a half years after construction has begun. Originally, the second level of the bridge was exclusive for vehicular traffic while the lower level was meant for train tracks. However, due to the increasing number of cars using the bridge, the train tracks were later on removed and both levels were used for vehicular traffic.
The blueprint of the Bay Bridge was made by civil engineer Charles H. Purcell. When it was completed, it was the longest and most expensive bridge in the planet costing more than 77 million dollars. It is composed of two segments adjoined by a tunnel found in Yerba Buena Island. Because of the varying soil properties and water depth on the two ends of the Yerba Buena Island, Purcell made two different designs. The western segment which is in close proximity to San Francisco is comprised of suspension bridges coupled with high altitude towers and lengthy spans while the eastern part is characterized by one suspension bridge and an expansive viaduct.
In 1989, a magnitude 6.9 earthquake damaged the eastern section of the Bay Bridge. After that, efforts to make the bridge seismic proof have been put into place and building of a new eastern section began in 2002. To be fully completed in 2013, the design which is made of 385-meter long steel Self-Anchored Supension will be the earth?s most lengthy, single-tower bridge of its kind.
Today, the Bay Bridge accommodates an estimated 270,000 vehicles per day. The width of the two decks measures 57.5 feet each and enables five lanes going in each direction. Vehicles going westward going to San Francisco use the upper deck while vehicles going to Oakland utilize the lower deck.
The unofficial name of the bridge is the James ?Sunny Jim? Rolph bridge but it was not widely used and most San Franciscans call it The Bay Bridge.