Alvord Lake Bridge

37°46′08″N 122°27′18″W / 37.7690°N 122.4549°W / 37.7690; -122.4549Carries3 lanes of Kezar DriveCrossesPedestrian entrance to Golden Gate ParkLocaleSan FranciscoOfficial nameAlvord Lake BridgeHeritage statusAmerican Society of Civil Engineers civil engineering landmarkCharacteristicsMaterialReinforced concreteWidth64 ft (20 m)Longest span20 ft (6.1 m)No. of spans1HistoryDesignerErnest L. RansomeOpened1889Location

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 and the interior features sculpted concrete "stalactites" created during the initial construction to give the bridge underpass a faux cave-like appearance.^[2]

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 in 1969.

The Alvord Lake Bridge, which arches over a pedestrian walkway near the lake in San Francisco's Golden Gate Park, allows visitors coming from the Haight Ashbury 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 the busy Kezar Drive.

See also

• List of bridges documented by the Historic American Engineering Record in California
• Smith-Ransome Japanese Bridge
• Fernbridge – longest poured reinforced concrete bridge in the world

References

External links

• Historic American Engineering Record (HAER) No. CA-33, "Alvord Lake Bridge", 4 photos, 2 data pages, 1 photo caption page
• Alvord Lake Bridge 1890s photograph of original interior
• Circa 1910 photograph of bridge, interior visible
• American Society of Civil Engineers – National Historic Civil Engineering Landmark
• Media related to Alvord Lake Bridge at Wikimedia Commons