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Friday, 25 May 2018

27 May 1937 – In California, the Golden Gate Bridge

              Golden Gate Bridge







27 May 1937 – In California, the Golden Gate Bridge opens to pedestrian traffic, creating a vital link between San Francisco and Marin County, California.
The Golden Gate Bridge is a suspension bridge spanning the Golden Gate, the one-mile-wide (1.6 km) strait connecting San Francisco Bay and the Pacific Ocean. The structure links the American city of San Francisco, California – the northern tip of the San Francisco Peninsula – to Marin County, carrying both U.S. Route 101 and California State Route 1 across the strait. The bridge is one of the most internationally recognized symbols of San Francisco, California, and the United States. It has been declared one of the Wonders of the Modern World by the American Society of Civil Engineers.[7]
The Frommer's travel guide describes the Golden Gate Bridge as "possibly the most beautiful, certainly the most photographed, bridge in the world."[8][9] At the time of its opening in 1937, it was both the longest and the tallest suspension bridge in the world, with a main span of 4,200 feet (1,280 m) and a total height of 746 feet (227 m).

Ferry service

Golden Gate with Fort Point in foreground, c. 1891
Before the bridge was built, the only practical short route between San Francisco and what is now Marin County was by boat across a section of San Francisco Bay. A ferry service began as early as 1820, with a regularly scheduled service beginning in the 1840s for the purpose of transporting water to San Francisco.[10]
The Sausalito Land and Ferry Company service, launched in 1867, eventually became the Golden Gate Ferry Company, a Southern Pacific Railroad subsidiary, the largest ferry operation in the world by the late 1920s.[10][11]

Conception

Although the idea of a bridge spanning the Golden Gate was not new, the proposal that eventually took hold was made in a 1916 San Francisco Bulletin article by former engineering student James Wilkins.[16] San Francisco's City Engineer estimated the cost at $100 million, which would have been $2.12 billion in 2009, and impractical for the time. He asked bridge engineers whether it could be built for less.[10] One who responded, Joseph Strauss, was an ambitious engineer and poet who had, for his graduate thesis, designed a 55-mile-long (89 km) railroad bridge across the Bering Strait.[17] At the time, Strauss had completed some 400 drawbridges—most of which were inland—and nothing on the scale of the new project.[3] Strauss's initial drawings[16] were for a massive cantilever on each side of the strait, connected by a central suspension segment, which Strauss promised could be built for $17 million.[10]
Local authorities agreed to proceed only on the assurance that Strauss would alter the design and accept input from several consulting project experts.[citation needed] A suspension-bridge design was considered the most practical, because of recent advances in metallurgy.[10]

Design

South tower seen from walkway, with Art Deco elements
Strauss was chief engineer in charge of overall design and construction of the bridge project.[14] However, because he had little understanding or experience with cable-suspension designs,[22] responsibility for much of the engineering and architecture fell on other experts. Strauss's initial design proposal (two double cantilever spans linked by a central suspension segment) was unacceptable from a visual standpoint. The final graceful suspension design was conceived and championed by Leon Moisseiff, the engineer of the Manhattan Bridge in New York City.[23]
Irving Morrow, a relatively unknown residential architect, designed the overall shape of the bridge towers, the lighting scheme, and Art Deco elements, such as the tower decorations, streetlights, railing, and walkways. The famous International Orange color was originally used as a sealant for the bridge.[24] The US Navy had wanted it to be painted with black and yellow stripes to ensure visibility by passing ships.[14]
Senior engineer Charles Alton Ellis, collaborating remotely with Moisseiff, was the principal engineer of the project.[25] Moisseiff produced the basic structural design, introducing his "deflection theory" by which a thin, flexible roadway would flex in the wind, greatly reducing stress by transmitting forces via suspension cables to the bridge towers.[25] Although the Golden Gate Bridge design has proved sound, a later Moisseiff design, the original Tacoma Narrows Bridge, collapsed in a strong windstorm soon after it was completed, because of an unexpected aeroelastic flutter.[26] Ellis was also tasked with designing a "bridge within a bridge" in the southern abutment, to avoid the need to demolish Fort Point, a pre–Civil War masonry fortification viewed, even then, as worthy of historic preservation. He penned a graceful steel arch spanning the fort and carrying the roadway to the bridge's southern anchorage.[27]



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