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 |
| Locale | San Francisco |
| Official name | Alvord Lake Bridge |
| Heritage status | American Society of Civil Engineers civil engineering landmark |
| Characteristics | |
| Material | Reinforced concrete |
| Width | 64ft |
| Longest span | 20ft |
| Number of spans | 1 |
| History | |
| Designer | Ernest L. Ransome |
| Opened | 1889 |
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 .[1] 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 concrete "stalactites" (some of which have subsequently grown due to redeposition of limestone from the concrete).
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 Alvord Lake Bridge, which arches over a pedestrian entrance to San Francisco's Golden Gate park, was designated a civil engineering landmark by the American Society of Civil Engineers in 1969.
References
Coordinates: 37°46′08″N 122°27′18″W / 37.7690°N 122.4549°W