San Francisco County, California Bridges: Southern Freeway Viaduct

July 2014 (37.7712 Degrees, -122.3978 Degrees) Southern Freeway Viaduct

A photo of the Southern Freeway Viaduct crossing Islais Creek. At this location the columns have been cased in steel jackets to prevent the bridge from collapsing during future earthquakes. In the background is the 1000 ft tall Sutro Tower, which was originally built to provide TV reception to the city. Behind it are the hills and mountains of San Francisco.

San Francisco County, California Bridges: Southern Freeway Viaduct by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

San Francisco County, California Bridges: Alemany Interchange

December 1998 (37.7352 Degrees, -122.4094 Degrees) Alemany Interchange

South of the Central Freeway Viaduct, Highway 101 and 280 come together at the Alemany Maze (34 0070). This  complicated interchange is composed of short stiff piers, big strong piers, and tall flexible piers. An innovative retrofit was developed that used isolation to make the different substructure elements move together during the design earthquake. The stiff members had flexible isolators that allowed the superstructure to displace. The strong members used isolators to prevent the columns from damaging the weaker bent caps. The flexible members were free to move without causing damage to stiff or weak elements.

San Francisco County, California Bridges: Alemany Interchange by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

San Francisco County, California Bridges: Central Freeway Viaduct

July 2014 (37.76924 Degrees, -122.40890 Degrees) Central Freeway Viaduct

South of yesterday's West Approach to the Bay Bridge is the mile long Central Freeway Viaduct. At one time it was planned to make the viaduct part of an elevated loop around the city, but after it was damaged during the Loma Prieta earthquake it was torn down except for the portion that connects Mission Street to the 101/I-80. The Central Viaduct is made of steel columns and steel girders and so it was difficult to increase its seismic resistance. Doubler plates and restrainers were added to improve it's displacement capacity.

San Francisco County, California Bridges: Central Freeway Viaduct by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.