Cypress Street Viaduct
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The Cypress Street Viaduct was a 2-kilometer long, raised two-tier, multi-lane (five lanes per deck) freeway constructed of reinforced concrete that was once part of Interstate 880 in Oakland, California. 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 the Loma Prieta Earthquake occurred on October 17, 1989 when much of the upper tier collapsed onto the lower tier resulting in 42 fatalities.
When in use, the upper tier was used by southbound traffic, and the lower tier was used by northbound traffic. Some sections of the Cypress Steet Viaduct were largely supported by two columns on either side, but some sections were only supported beneath by a single supporting column. The design was deficient since the upper portions of the exterior columns were not tied by reenforcing to the lower columns, and the columns were not sufficiently ringed to prevent bursting. At the time of its design such structures were not analysed as a whole, and it appears that large structure motion was contrbutory to the collapse. It was built on filled land, which is highly susceptible to soil liquefaction during an earthquake and exhibits larger ground motion.
The viaduct was torn down, and the corridor became known as Mandela Parkway (in honor of Nelson Mandela) with a landscaped median where the structure once stood. Interstate 880 was rerouted to loop around the area using a more conventional single level viaduct design. [link]
Similar structures damaged by earthquakes
External links
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