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Cypress Street Viaduct
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Cypress Street Viaduct
The Cypress Street Viaduct, often referred to as the Cypress Structure or the Cypress Freeway, was a 1.6-mile-long (2.6 km), raised two-deck, multi-lane (four lanes per tier) freeway constructed of reinforced concrete that was originally part of the Nimitz Freeway (State Route 17, and later, Interstate 880) in Oakland, California, United States.
It replaced an earlier single-deck viaduct constructed in the 1930s as one of the approaches to the San Francisco–Oakland Bay Bridge. It was located along Cypress Street between 7th Street and Interstate 80 in the West Oakland neighborhood.
It officially opened to traffic on June 11, 1957, and was in use until October 17, 1989. At approximately 5:04 p.m. that day, a magnitude 6.9 earthquake struck the Bay Area, resulting in a large portion of the freeway's upper deck collapsing onto the lower deck. The collapse killed 42 people and resulted in the subsequent demolition of the structure.
The Cypress Freeway Memorial Park is located in Oakland, at 14th Street and Mandela Parkway.
The double-decked viaduct was initially designed in 1949 by the City of Oakland as a way to ease traffic on local streets leading to the Bay Bridge, such as Cypress Street (which was California State Route 17 at the time). The route was supposedly chosen to displace perceived slums in West Oakland.
The southernmost portion of the Cypress Street viaduct, which was designed as a central off ramp structure exiting at Market Street between Fifth and Sixth Streets to the Eighth Street/Seventh Street on/off ramps, was the first phase of the overall project completed in October 1955, by contractors Frederickson and Watson at a cost of $1.7 million. Construction on the second phase of the project, the double-decked viaduct portion (which started from Adeline Street in the south to the MacArthur Maze in the north), began in February 1956 by contractors Grove, Wilson, Shepard and Kruge at a cost of $8.3 million, bringing the total cost of the viaduct project to $10 million. It was California's first double-decked freeway when it officially opened to traffic on June 11, 1957.
On October 17, 1989, the portion of the structure from 16th Street north to the MacArthur Maze collapsed during the 1989 Loma Prieta earthquake, due to ground movement and structural flaws.
The upper deck was used by southbound traffic; the lower deck, by northbound traffic. Some sections of the Cypress Street Viaduct were largely supported by two columns on either side, but some sections were only supported by a single supporting column. The design was unable to survive the earthquake because the upper portions of the exterior columns were not tied by reinforcing to the lower columns, and the columns were not sufficiently ringed to prevent bursting (similar to Hanshin Expressway in Kobe, Japan). At the time of its design, such structures were not analyzed as a whole, and it appears that large structure motion contributed to the collapse. It was built on filled land on top of bay clay; filled land is highly susceptible to soil settlement during an earthquake, and bay clay exhibits larger ground motion. A small degree of earthquake reinforcement was added to the Cypress Street Viaduct in 1977.
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Cypress Street Viaduct
The Cypress Street Viaduct, often referred to as the Cypress Structure or the Cypress Freeway, was a 1.6-mile-long (2.6 km), raised two-deck, multi-lane (four lanes per tier) freeway constructed of reinforced concrete that was originally part of the Nimitz Freeway (State Route 17, and later, Interstate 880) in Oakland, California, United States.
It replaced an earlier single-deck viaduct constructed in the 1930s as one of the approaches to the San Francisco–Oakland Bay Bridge. It was located along Cypress Street between 7th Street and Interstate 80 in the West Oakland neighborhood.
It officially opened to traffic on June 11, 1957, and was in use until October 17, 1989. At approximately 5:04 p.m. that day, a magnitude 6.9 earthquake struck the Bay Area, resulting in a large portion of the freeway's upper deck collapsing onto the lower deck. The collapse killed 42 people and resulted in the subsequent demolition of the structure.
The Cypress Freeway Memorial Park is located in Oakland, at 14th Street and Mandela Parkway.
The double-decked viaduct was initially designed in 1949 by the City of Oakland as a way to ease traffic on local streets leading to the Bay Bridge, such as Cypress Street (which was California State Route 17 at the time). The route was supposedly chosen to displace perceived slums in West Oakland.
The southernmost portion of the Cypress Street viaduct, which was designed as a central off ramp structure exiting at Market Street between Fifth and Sixth Streets to the Eighth Street/Seventh Street on/off ramps, was the first phase of the overall project completed in October 1955, by contractors Frederickson and Watson at a cost of $1.7 million. Construction on the second phase of the project, the double-decked viaduct portion (which started from Adeline Street in the south to the MacArthur Maze in the north), began in February 1956 by contractors Grove, Wilson, Shepard and Kruge at a cost of $8.3 million, bringing the total cost of the viaduct project to $10 million. It was California's first double-decked freeway when it officially opened to traffic on June 11, 1957.
On October 17, 1989, the portion of the structure from 16th Street north to the MacArthur Maze collapsed during the 1989 Loma Prieta earthquake, due to ground movement and structural flaws.
The upper deck was used by southbound traffic; the lower deck, by northbound traffic. Some sections of the Cypress Street Viaduct were largely supported by two columns on either side, but some sections were only supported by a single supporting column. The design was unable to survive the earthquake because the upper portions of the exterior columns were not tied by reinforcing to the lower columns, and the columns were not sufficiently ringed to prevent bursting (similar to Hanshin Expressway in Kobe, Japan). At the time of its design, such structures were not analyzed as a whole, and it appears that large structure motion contributed to the collapse. It was built on filled land on top of bay clay; filled land is highly susceptible to soil settlement during an earthquake, and bay clay exhibits larger ground motion. A small degree of earthquake reinforcement was added to the Cypress Street Viaduct in 1977.
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