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San fraoncisco is called the cite of Golden gate Brige
The Golden Gate Bridge is a suspension bridge spanning the Golden Gate, the opening into the San Francisco Bay from the Pacific Ocean. It connects the city of San Francisco on the northern tip of the San Francisco Peninsula and a portion of the south-facing Marin County headlands near the small bayside town of Sausalito, and is located at 37°49′12″N, 122°28′43″W.[1] The entire bridge (including the approach) spans 1.7 miles (2.7 km) long; the distance between the towers ("main span") is 4,200 feet (1,280 m), and the clearance below the bridge is 220 ft (67 m) at mean high water. The two towers rise 746 feet (227 m) above the water. The diameter of the main suspension cables is 1 yard (0.91 m).
The Golden Gate Bridge was the largest suspension bridge in the world when it was completed in 1937 and has become an internationally recognized symbol of San Francisco. It is currently the second longest in the United States after the Verrazano-Narrows Bridge in New York City.
History
The idea of a bridge that would cross the Golden Gate Strait and link San Francisco to Marin County (then done by ferry) was brought up in an article by the engineer James Wilkins.[2] The bridge later earned its name, Golden Gate Bridge, after a mention of it in 1917, by San Francisco city engineer M. M. O’Shaughnessy.[3]
The bridge was the brainchild of Joseph Strauss, an engineer responsible for over 400 drawbridges, though they were far smaller than this project and mostly inland.[1] Starting in 1921 with his first drawings that were far from approved[2], Strauss spent over a decade drumming up support in Northern California. Strauss's initial design [4] comprised a massive cantilever on each side connected with a central suspension segment. Other key figures in the bridge's construction include architect Irving Morrow, responsible for the Art Deco touches and the choice of color, and engineer Charles Alton Ellis and bridge designer Leon Moisseiff, who collaborated on the complicated mathematics involved.
In May 1924, a hearing, through a petition, was heard by Colonel Herbert Deakyne for the Secretary of War in a request to use land for the construction of the Golden Gate Bridge. Col. Deakyne, in the Secretary of War's name, approved to give the land needed for the bridge structure and leading roads to the "Bridging the Golden Gate Association" and both the San Francisco and the Marin counties pending further bridge plans by Mr. Strauss.[5]
The bridge spans the Golden GateThe Golden Gate Bridge and Highway District was incorporated in 1928 as the official entity to design, construct, and finance the Golden Gate Bridge. The District includes not only the City & County of San Francisco, and Marin County, in whose boundaries the bridge sits, but also Napa, Sonoma, Mendocino and Del Norte counties. Representatives from each of the six counties sit on the District's Board of Directors. Voters within the District approved funding for the project in 1930 through a special bond issue that put their homes, farms and business properties up as collateral. This bond issue raised the initial $35 million to finance the building of the Bridge. Construction began on January 5, 1933.[6] The last of the construction bonds were retired in 1971, with $35 million in principal and nearly $39 million in interest being financed entirely from tolls. Strauss, a graduate of the University of Cincinnati, placed a brick from his alma mater's demolished McMicken Hall in the south anchorage before the concrete was poured.
The bridge was completed in April 1937 and opened to pedestrians on May 27 of that year. The next day, President Roosevelt pushed a button in Washington, DC signaling the official start of vehicle traffic over the Bridge at noon. A unique aspect of the bridge's construction was the safety net set up beneath it, significantly reducing the expected number of deaths for such a project. 11 men were killed from falls during construction, and approximately 19 men were saved by the safety net. 10 of the deaths occurred near completion, when the net itself failed under the stress of a scaffold fall. The 19 workers whose lives were saved by the safety nets became proud members of the (informal) Halfway to Hell Club.
A photograph of the bridge from a boat underneath.Since its completion, the bridge was closed due to windy conditions only three times, in 1951, 1982 and 1983.[7]
To commemorate Joseph Strauss for his part taken in the construction of the bridge, a statue of him was relocated in 1955 near the structure to remind people how important his work was in the building of the Golden Gate Bridge.[2]
The center span was the longest among suspension bridges until 1964 when the Verrazano Narrows Bridge was erected between the boroughs of Staten Island and Brooklyn in New York City. The Golden Gate Bridge also had the world's tallest suspension towers at the time of construction, and retained that record until more recently. In 1957, Michigan's Mackinac Bridge surpassed the Golden Gate Bridge's length to become the world's longest two tower suspension bridge in total length between anchorages. The longest center suspension span in the world and the longest two tower suspension bridge between anchorages is currently the Akashi-Kaikyo Bridge in Japan.
As the only road to exit San Francisco to the north, the bridge is part of both U.S. Route 101 and California State Route 1 and on an average day there are 100,000 vehicles crossing the bridge.[1] The bridge has six total lanes of vehicle traffic, and walkways on both sides of the bridge. The median markers between the lanes are moved to conform to traffic patterns. On weekday mornings, traffic flows mostly southbound into the city, so four of the six lanes run southbound. Conversely, on weekday afternoons, four lanes run northbound. While there has been discussion concerning the installation of a movable barrier since the 1980s, the Bridge Board of Directors, in March 2005, committed to finding funding to complete the $2 million study required prior to the installation of a moveable median barrier. The eastern walkway is for pedestrians and bicycles during the weekdays and during daylight hours only, and the western walkway is open to bicyclists on weekday afternoons, weekends, and holidays.
The speed limit on the Golden Gate Bridge was reduced from 55 mph (90 km/h) to 45 mph (70 km/h) on October 1, 1983. With no moveable median barrier yet, a head-on collision at 55 mph (90 km/h) would create almost 1.5 times the force than at 45 mph (70 km/h).
On September 1, 2002, the toll for Southbound motor vehicles was raised from US$3.00 to $5.00. Northbound motor vehicle traffic, cycling, and pedestrian traffic remain toll free.[8]
Aesthetics
The Golden Gate Bridge by night, with part of downtown San Francisco visible in the background at far left.The color of the bridge is orange vermilion, deemed International Orange. The color was selected by consulting architect Irving Morrow because it blends well with the natural surroundings yet enhances the bridge's visibility in fog. The bridge is widely considered one of the most beautiful examples of bridge engineering, both as a structural design challenge and for its aesthetic appeal. It was declared one of the modern Wonders of the World by the American Society of Civil Engineers. According to Frommer's travel guide, the Golden Gate Bridge is "possibly the most beautiful, certainly the most photographed, bridge in the world." [9] (although Frommers also bestows the "most photographed" honor on Tower Bridge [10])
Aesthetic was the foremost reason why the first design of Joseph Strauss was rejected but upon re-submission of his bridge construction plan, he added attracting details, like lighting to outline the bridge's cables and towers, that gave the bridge fame and brought people to come and take pictures of it. It then became the way the salesmen attracted visitors to the San Francisco Bay Area.[11]
The Golden Gate Bridge has a similar sister bridge in Lisbon, Portugal. The red-painted Ponte 25 de Abril (25th April Bridge) is 2,278 Meters long and spans 1,013 Meters.
Paintwork
The bridge was originally painted with red lead primer and a lead-based topcoat, which was touched up as required. In the mid-1960s, a program was started to improve corrosion protection by stripping the original paint off and repainting the bridge with zinc silicate primer and, originally, vinyl topcoats [12] [13]. Acrylic topcoats have been used instead since 1990 for air quality reasons. The program was completed in 1995, and there is now ongoing maintenance by 38 painters [14] to touch up the paintwork where it becomes seriously eroded. |
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