Alvord Lake Bridge
|Alvord Lake Bridge|
A view of the Alvord Lake Bridge looking toward the east
|Crosses||Pedestrian entrance to San Francisco's Golden Gate park|
|Official name||Alvord Lake Bridge|
|Heritage status||American Society of Civil Engineers civil engineering landmark|
|No. of spans||1|
|Designer||Ernest L. Ransome|
The Alvord Lake Bridge was the first reinforced concrete bridge built in America. It was built in 1889 by Ernest L. Ransome, an innovator in reinforced concrete design, mixing equipment, and construction systems. The bridge was constructed as a single arch 64 feet (20 m) wide with a 20-foot (6.1 m) 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, the interior features calthemite  "stalactites" (concrete derived secondary deposits) which have subsequently grown in later years after the initial construction.
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.
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