The Alvord Lake Bridge was the first

reinforced concrete Reinforced concrete (RC), also called reinforced cement concrete (RCC) and ferroconcrete, is a composite material in which concrete's relatively low tensile strength and ductility are compensated for by the inclusion of reinforcement having hig ...

bridge built in America. It was built in 1889 by

Ernest L. Ransome Ernest Leslie Ransome (1844–1917) was an English-born engineer, architect, and early innovator in reinforced concrete building techniques. Ransome devised the most sophisticated concrete structures in the United States at the time. Ernest was ...

, an innovator in reinforced concrete design, mixing equipment, and construction systems. The bridge was constructed as a single arch wide with a span . Ransome is believed to have used his patented cold-twisted square steel bar for reinforcement, placed longitudinally in the arch and curved in the same arc. The face of the bridge was scored and hammered to resemble sandstone and the interior features sculpted concrete "stalactites" created during the initial construction to give the bridge underpass a faux cave-like appearance. E. L. Ransome left San Francisco a few years later, frustrated and bitter at the building community's indifference to concrete construction. Ironically, the city's few reinforced concrete structures, including the Alvord Lake Bridge, survived the 1906 earthquake and fire in remarkable shape, vindicating Ransome's faith in the method. The bridge was designated a historic civil engineering landmark by the

American Society of Civil Engineers American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...

in 1969. The Alvord Lake Bridge, which arches over a pedestrian walkway near the lake in San Francisco's

Golden Gate Park Golden Gate Park, located in San Francisco, California, United States, is a large urban park consisting of of public grounds. It is administered by the San Francisco Recreation & Parks Department, which began in 1871 to oversee the development ...

, allows visitors coming from the

Haight Ashbury Haight-Ashbury () is a district of San Francisco, California, named for the intersection of Haight and Ashbury streets. It is also called The Haight and The Upper Haight. The neighborhood is known as one of the main centers of the counterculture ...

District and entering the park from the east at Stanyan Street to access the rest of the park safely and directly by providing a grade-separated crossing underneath busy Kezar Drive.

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Alvord Lake Bridge 1890s photograph of original interiorCirca 1910 photograph of bridge, interior visibleAmerican Society of Civil Engineers - National Historic Civil Engineering Landmark
Bridges completed in 1889 Bridges in San Francisco Golden Gate Park Historic Civil Engineering Landmarks Historic American Engineering Record in California Road bridges in California Concrete bridges in California Arch bridges in the United States {{SanFrancisco-struct-stub

See also

References

External links