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San Francisco - Oakland Bay Bridge, California
The San Francisco - Oakland Bay Bridge is often simply called the Oakland Bay Bridge or locally just the Bay Bridge. Microsoft's Encarta CD-ROM encyclopedia refers to it as the Transbay Bridge but I have not seen or heard this name used elsewhere. Incidentally, the Transbay Transit Terminal is a building fairly close to the bridge's western end, originally used as a terminus for the street-cars which once used the bridge; it is now used as a terminus by a variety of bus companies, both local and long distance. The Transbay Tube is an underwater tube, built in a trench, through which the BART tracks run between San Francisco and Oakland.
The San Francisco - Oakland Bay Bridge carries I-80 between the cities of San Francisco and Oakland, over San Francisco Bay.
The structure actually consists of three separate bridges and a viaduct. Two suspension bridges (not side by side but one suspension bridge followed by another, other words in series, not in parallel) cross the West Bay, connecting the city of San Francisco to Yerba Buena Island in the middle of the bay. A tunnel and viaduct carry the road through the island. A steel girder cantilever and truss bridge connects the Yerba Buena island to the East Bay.
A massive cuboid-shaped concrete pier between the two suspension bridges acts as an anchorage for one end of each of the bridges' supporting cables.
The suspension bridges' four towers (two per bridge) have diagonal struts both above and below the roadway decks, connecting the two parts of each tower which lie on either side of the roadway. On each of the four towers these diagonal struts form three "X"'s above the roadway and two "X"'s below it. There is a single horizontal strut joining the tops of each tower.
The suspension bridges' four towers are silver in colour. However, due to the effect of lighting they can appear white or even black, especially at night. This is probably due to the silver reflecting the colour of the sky or the water. My grateful thanks to Christof Spieler of the Department of Civil Engineering at Rice University, Houston, Texas, who maintains their excellent Bridges Project web site, who kindly emailed me to explain the variation in the towers' apparent colour.
The two suspension bridges which form part of the San Francisco - Oakland Bay bridge can therefore be distinguished from the nearby Golden Gate Bridge by the following features:
- The San Francisco - Oakland Bay Bridge has two suspension bridges and therefore four towers. The Golden Gate Bridge has two towers.
- The San Francisco - Oakland Bay Bridge suspension bridges' four towers have diagonal struts above and below the road decks, forming three "X"'s above and two "X"'s below. There is a single horizontal strut joining the tops of each tower. Each of the Golden Gate Bridge's two towers have four horizontal struts above the roadway and below the roadway each tower has horizontal and diagonal struts which form two "X"'s.
- The San Francisco - Oakland Bay Bridge suspension bridges' four towers are silver in colour, although they may appear white or black in some photographs. The Golden Gate Bridge's two towers are red in colour.
- The entire structure of the San Francisco - Oakland Bay Bridge (all the bridges, the tunnel and viaduct through Yerba Buena Island and the approach roads) has two decks, one for traffic in each direction, unfortunately making it a rather utilitarian structure and seriously restricting the views for eastbound vehicles which use the lower deck. Each deck carries five lanes of traffic. The lower deck carries eastbound traffic, the upper deck westbound. Originally one deck was used for road traffic and the other carried streetcars. The Golden Gate bridge only has one level of roadway.
The length of the entire structure of the San Francisco - Oakland Bay Bridge, with approaches, is 8.4 miles (or 7.5 miles - sources vary), of which 4.5 miles is over water. The combined length of the two suspension bridges which cross the West Bay is 9260 feet with two 2310 feet suspension spans. The bottom of the lower deck is 220 feet above the water level and the tops of its towers are 526 feet above the water level. The length of the cantilever and truss bridge which crosses the East Bay is 10,176 feet with a cantilever span of 1400 feet. The cantilever and truss bridge was the longest of its kind in the world at the time of its opening and it has the world's deepest bridge pier, 242 feet below the water level. The tunnel through the island is the largest bore tunnel in the world, having a width of 76 feet, a height of 56 feet (or 58 feet, sources vary) and a length of 1700 feet (or 500 feet - sources vary). The structure also includes an 800 foot long viaduct on the island. Construction of the bridge consumed over six percent of the total steel output of the USA in 1933.
The bridge was opened in 1936. Initially the upper deck was used by cars and the lower deck by larger vehicles and street cars. The bridge was modified in 1958 to the current arrangement for the use of each deck. In 1989 part of the bridge was damaged by the Loma Prieta earthquake but this was quickly repaired.
According to two separate sources the toll for normal cars is $2, westbound only, collected at the eastern end (autumn 2002). There was no toll eastbound when I last crossed the bridge in June 2000.
According to one source, there is a plan to replace the East Bay section of the bridge with a cable-stayed bridge.
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About this personal web site JohnCletheroe
EMail me While I have an interest in the subject of bridges, I am not an expert. Therefore I regrettably cannot offer any information on the subject other than that which appears on these pages.
Most recently modified 6-Jun-03