Golden Gate Bridge in San Francisco

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The Golden Gate Bridge is a suspension bridge spanning the Golden Gate, the opening of the San Francisco Bay into the Pacific Ocean. As part of both U.S. Route 101 and California State Route 1, the structure links the city of San Francisco, on the northern tip of the San Francisco Peninsula, to Marin County. It is one of the most internationally recognized symbols of San Francisco, California, and of the United States. It has been declared one of the modern Wonders of the World by the American Society of Civil Engineers. The Frommers travel guide considers the Golden Gate Bridge "possibly the most beautiful, certainly the most photographed, bridge in the world".

History

Ferry service

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. Ferry service began as early as 1820, with regularly scheduled service beginning in the 1840s for purposes of transporting water to San Francisco. 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. Once for railroad passengers and customers only, Southern Pacific's automobile ferries became very profitable and important to the regional economy. The ferry crossing between the Hyde Street Pier in San Francisco and Sausalito in Marin County took approximately 20 minutes and cost US$1.00 per vehicle, a price later reduced to compete with the new bridge. The trip from the San Francisco Ferry Building took 27 minutes.

Many wanted to build a bridge to connect San Francisco to Marin County. San Francisco was the largest American city still served primarily by ferry boats. Because it did not have a permanent link with communities around the bay, the city's growth rate was below the national average. Many experts said that a bridge couldn’t be built across the 6700 ft strait. It had strong, swirling tides and currents, with water 500 ft in depth at the center of the channel, and frequent strong winds. Experts said that ferocious winds and blinding fogs would prevent construction and operation. San Francisco's City Engineer estimated the cost at $100 million, impractical for the time, and fielded the question to bridge engineers of whether it could be built for less. At the time, Strauss had completed some 400 drawbridges—most of which were inland—and nothing on the scale of the new project. Strauss's initial drawings responsibility for much of the engineering and architecture fell on other experts. Strauss' 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 New York’s Manhattan Bridge designer Leon Moisseiff.

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 streetlights, railing, and walkways. The famous International Orange color was originally used as a sealant for the bridge. Many locals persuaded Morrow to paint the bridge in the vibrant orange color instead of the standard silver or gray, and the color has been kept ever since. The US Navy had wanted it to be painted with black and yellow stripes to ensure visibility by passing ships. 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. Only much later were the contributions of the others on the design team properly appreciated.

Description

Specifications

When completed in 1937, the Golden Gate Bridge had the longest suspension bridge main span in the world, at 4,200 feet (1,280.2 m). Since 1964, its main span length has been surpassed by eight other bridges. However, it still has the second longest main span in the United States, after the Verrazano-Narrows Bridge in New York City.

The total length of the Golden Gate Bridge, including approaches from abutment to abutment, is 8,981 feet (2,737 m).

At 692 feet (211m) (above water), the Golden Gate Bridge also had the world's tallest suspension towers when built. It held that status until 1998, with the completion of bridges in Denmark and Japan.

Structure

The weight of the roadway is hung from two cables that pass through the two main towers and are fixed in concrete at each end. Each cable is made of 27,572 strands of wire. There are 80,000 miles (129,000 km) of wire in the main cables. The bridge has approximately 1,200,000 total rivets.

Traffic

As the only road to exit San Francisco to the north, the bridge is part of both U.S. Route 101 and California Route 1. 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. Although there has been discussion concerning the installation of a movable barrier since the 1980s, only in March 2005 did the Bridge Board of Directors commit to finding funding to complete the $2 million study required prior to the installation of a movable median barrier.

The bridge is popular with pedestrians and bicyclists as well as cars, and was built with walkways on either side of the six traffic lanes. Initially, they were separated by the traffic lanes by only a metal curb, but railings between the walkways and the traffic lanes were added in 2003, primarily as a measure to prevent runaway cyclists from falling into the roadway.

In November 2006, the Golden Gate Bridge, Highway and Transportation District recommended a corporate sponsorship program for the bridge to address its operating deficit, projected at $80 million over five years. The District promised that the proposal, which it called a "partnership program", would not include changing the name of the bridge or placing advertising on the bridge itself. In October 2007, the Board unanimously voted to discontinue the proposal and seek additional revenue through other means, most likely a toll increase.

On September 2, 2008, the auto cash toll for all southbound motor vehicles was raised from $5 to $6, and the FasTrak toll was increased from $4 to $5. Bicycle, pedestrian, and northbound motor vehicle traffic remain toll free. For vehicles with more than two axles, the toll rate is $2.50 per axle.

In an effort to save $19.2 million over the following 10 years, the Golden Gate District voted in January 2011 to eliminate all toll takers by 2012 and strictly use open road tolling only.

Congestion pricing

In March 2008, the Golden Gate Bridge District board approved a resolution to implement congestion pricing at the Golden Gate Bridge, charging higher tolls during peak hours, but rising and falling depending on traffic levels. This decision allowed the Bay Area to meet the federal requirement to receive $158 million in federal transportation funds from USDOT Urban Partnership grant. As a condition of the grant, the congestion toll was to be in place by September 2009.

The first results of the study, called the Mobility, Access and Pricing Study (MAPS), showed that a congestion pricing program is feasible. The different pricing scenarios considered were presented in public meetings in December 2008

In August 2008, transportation officials killed the bridge toll congestion pricing program in favor of varying rates for metered parking along the route to the bridge including on Lombard Street and Van Ness Avenue

Suicides

More people die by suicide at the Golden Gate Bridge than at any other site in the world. The deck is approximately 245 ft above the water. After a fall of approximately four seconds, jumpers hit the water at around 75 mph or approximately 120 km/h. Most jumpers die from impact trauma on contact with the water. The few who survive the initial impact generally drown or die of hypothermia in the cold water.

Most suicidal jumps occur on the side facing the bay. The side facing the Pacific is closed to pedestrians.

An official suicide count was kept, sorted according to which of the bridge's 128 lamp posts the jumper was nearest when he or she jumped. By 2005, this count exceeded 1,200 and new suicides were occurring about once every two weeks. For comparison, the reported second-most-popular place to commit suicide in the world, Aokigahara Forest in Japan, has a record of 78 bodies, found within the forest in 2002, with an average of 30 a year. There were 34 bridge-jump suicides in 2006 whose bodies were recovered, in addition to four jumps that were witnessed but whose bodies were never recovered, and several bodies recovered suspected to be from bridge jumps. The California Highway Patrol removed 70 apparently suicidal people from the bridge that year.

There is no accurate figure on the number of suicides or successful jumps since 1937, because many were not witnessed. People have been known to travel to San Francisco specifically to jump off the bridge, and may take a bus or cab to the site; police sometimes find abandoned rental cars in the parking lot. Currents beneath the bridge are very strong, and some jumpers have undoubtedly been washed out to sea without ever being seen. The water may be as cold as 47 °F.

The fatality rate of jumping is roughly 98%. As of 2006, only 26 people are known to have survived the jump.<ref name = "jumpers"/> Those who do survive strike the water feet-first and at a slight angle, although individuals may still sustain broken bones or internal injuries. One young woman, Sara Rutledge Birnbaum, survived, but returned to jump again and died the second time. One young man survived a jump in 1979, swam to shore, and drove himself to a hospital. The impact cracked several of his vertebrae. On March 10, 2011, 17 year-old Luhe “Otter” Vilagomez from Windsor High School in Windsor, California survived a jump from the bridge, breaking his tailbone and puncturing one lung, though saying his attempt was for "fun" and not suicide.

Engineering professor Natalie Jeremijenko, as part of her Bureau of Inverse Technology art collective, created a "Despondency Index" by correlating the Dow Jones Industrial Average with the number of jumpers detected by "Suicide Boxes" containing motion-detecting cameras, which she claimed to have set up under the bridge. The boxes purportedly recorded 17 jumps in three months, far greater than the official count. The Whitney Museum, although questioning whether Jeremijenko's suicide-detection technology actually existed, nevertheless included her project in its prestigious Whitney Biennial.

Various methods have been proposed and implemented to reduce the number of suicides. The bridge is fitted with suicide hotline telephones, and staff patrol the bridge in carts, looking for people who appear to be planning to jump. Ironworkers on the bridge also volunteer their time to prevent suicides by talking or wrestling down suicidal people. The bridge is now closed to pedestrians at night. Cyclists are still permitted across at night, but must be buzzed in and out through the remotely controlled security gates. Attempts to introduce a suicide barrier have been thwarted by engineering difficulties, high costs, and public opposition. One recurring proposal had been to build a barrier to replace or augment the low railing, a component of the bridge's original architectural design. New barriers have eliminated suicides at other landmarks around the world, but were opposed for the Golden Gate Bridge for reasons of cost, aesthetics, and safety (the load from a poorly designed barrier could significantly affect the bridge's structural integrity during a strong windstorm).

Strong appeals for a suicide barrier, fence, or other preventive measures were raised once again by a well-organized vocal minority of psychiatry professionals, suicide barrier consultants, and families of jumpers after the release of the controversial 2006 documentary film The Bridge, in which filmmaker Eric Steel and his production crew spent one year (2004) filming the bridge from several vantage points, in order to film actual suicide jumps. The film caught 23 jumps, most notably that of Gene Sprague as well as a handful of thwarted attempts. The film also contained interviews with surviving family members of those who jumped; interviews with witnesses; and, in one segment, an interview with Kevin Hines who, as a 19-year-old in 2000, survived a suicide plunge from the span and is now a vocal advocate for some type of bridge barrier or net to prevent such incidents from occurring.

On October 10, 2008, the Golden Gate Bridge Board of Directors voted 14 to 1 to install a plastic-covered stainless-steel net below the bridge as a suicide deterrent. The net will extend 20 ft on either side of the bridge and is expected to cost $40–50 million to complete. However, lack of funding could delay the net's deployment.

Wind

Since its completion, the Golden Gate Bridge has been closed due to weather conditions only three times: on December 1, 1951, because of gusts of 69 mph; on December 23, 1982, because of winds of 70 mph; and on December 3, 1983, because of wind gusts of 75 mph.

Seismic retrofit

Modern knowledge of the effect of earthquakes on structures led to a program to retrofit the Golden Gate to better resist seismic events. The proximity of the bridge to the San Andreas Fault places it at risk for a significant earthquake. Once thought to have been able to withstand any magnitude of foreseeable earthquake, the bridge was actually vulnerable to complete structural failure (i.e., collapse) triggered by the failure of supports on the 320 ft arch over Fort Point. A $392 million program was initiated to improve the structure's ability to withstand such an event with only minimal (repairable) damage. One challenging undertaking is completing this program without disrupting traffic. A complex electrohydraulic synchronous lift system was custom built for construction of temporary support towers and a series of intricate lifts, transferring the loads from the existing bridge onto the temporary supports. This was completed with engineers from Balfour Beatty and Enerpac, accomplishing this task without disrupting day-to-day San Francisco commuter traffic. The retrofit's planned completion date is 2012.

Doyle Drive replacement project

The elevated approach to the Golden Gate Bridge through the San Francisco Presidio is popularly known as Doyle Drive, dating back to 1933, was named after Frank P. Doyle, director of the California State Automobile Association. The highway carries approximately 91,000 vehicles each weekday between downtown San Francisco and suburban Marin County. However, the road has been deemed "vulnerable to earthquake damage", has a problematic 4-lane design, and lacks shoulders. For these reasons, a San Francisco County Transportation Authority study recommended that the current outdated structure be replaced with a more modern, efficient, and multimodal transportation structure. Construction on the $1 billion replacement, known as the Presidio Parkway, began in December 2009 and is expected to be completed in 2013.

See also

  • The Bridge (2006 film)
  • Golden Gate – the body of water that the bridge crosses
  • Golden Gate Bridge in popular culture
  • List of historic civil engineering landmarks
  • List of longest suspension bridge spans
  • List of tallest bridges in the world
  • Suicide bridge
  • Suspension bridge

Further reading

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External links



Source en.wikipedia.org/wiki/Golden_Gate_Bridge