Golden Gate Bridge

Golden Gate Bridge

Golden Gate Bridge, across the Golden Gate from San Francisco to Marin Co., W Calif.; built 1933-37. Its overall length is 9,266 ft (2,824 m); its main span across the strait, 4,200 ft (1,280 m), is one of the longest bridges in the world. Joseph B. Strauss was the chief engineer.

Golden Gate Bridge, San Francisco.

Suspension bridge spanning the Golden Gate, San Francisco. From its completion in 1937 until the completion of New York's Verrazano-Narrows Bridge in 1964, it had the longest main span in the world, 4,200 ft (1,280 m). It remains incomparable in its magnificence. Its construction, supervised by Joseph B. Strauss (1870–1938), involved many difficulties: rapidly running tides, frequent storms and fogs, and the problem of blasting rock under deep water to plant earthquake-resistant foundations.

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The Golden Gate Bridge is a suspension bridge spanning the Golden Gate, the opening of the San Francisco Bay onto the Pacific Ocean. As part of both U.S. Route 101 and State Route 1, it connects the city of San Francisco on the northern tip of the San Francisco Peninsula to Marin County. The Golden Gate Bridge had the longest suspension bridge span in the world when it was completed in 1937 and has become an internationally recognized symbol of San Francisco and California. Since its completion, the span length has been surpassed by eight other bridges. It still has the second longest suspension bridge main span in the United States, after the Verrazano-Narrows Bridge in New York City. In 2007, it was ranked fifth on the List of America's Favorite Architecture by the American Institute of Architects.

Setting

The Golden Gate Bridge spans the Golden Gate, a narrow, deep strait that serves as the mouth of the San Francisco Bay, between San Francisco at the northernmost tip of the San Francisco Peninsula, and the Marin Headlands at the far southern end of Marin County. Although close by proximity, the two sides of the strait are separated by significant natural obstacles. Crossing the strait directly by boat is dangerous because of strong currents and lack of suitable landings. Ocean tides drive an average of 528 billion gallons (2 billion cubic meters) of water every six hours, at peak currents exceeding 5.6 miles per hour (2.5 m/s). Circumnavigating the Bay, however, involves a trip of several hundred miles and crossing several major rivers.

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 1868, which 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 per vehicle, a price later reduced to compete with the new bridge. The trip from the 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 strait. It had strong, swirling tides and currents, with water in depth at the center of the channel, and almost constant winds of . Experts said that ferocious winds and blinding fogs would prevent construction and operation.

Conception

Although the idea of a bridge spanning the Golden Gate was not new, the proposal that eventually took root was made in a 1916 San Francisco Bulletin article by former engineering student James Wilkins. 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. One who responded, Joseph Strauss, was an ambitious but dreamy engineer and poet who had for his graduate thesis designed a long railroad bridge across the Bering Strait. At the time, Strauss had completed some 400 drawbridges—most of which were inland—and nothing on the scale of the new project. Strauss' initial drawings 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. Strauss' design was widely derided as ugly.

Local authorities agreed to proceed only on the assurance that Strauss alter the design and accept input from several consulting project experts. A suspension bridge design was considered the most practical, because of recent advances in metallurgy.

Strauss spent more than a decade drumming up support in Northern California. The bridge faced opposition, including litigation, from many sources. The Department of War was concerned that the bridge would interfere with ship traffic. Unions demanded guarantees that local workers would be favored for construction jobs. Southern Pacific Railroad, one of the most powerful business interests in California, opposed the bridge as competition to its ferry fleet and filed a lawsuit against the project, leading to a mass boycott of the ferry service. In May 1924, Colonel Herbert Deakyne held the second hearing on the Bridge on behalf of the Secretary of War in a request to use Federal land for construction. Deakyne, on behalf of the Secretary of War, approved the transfer of land needed for the bridge structure and leading roads to the "Bridging the Golden Gate Association", and both San Francisco County and Marin County, pending further bridge plans by Strauss. Another ally was the fledging automobile industry, which supported the development of roads and bridges to increase demand for automobiles.

The bridge earned its name, Golden Gate Bridge, after a mention of it in 1927 by San Francisco city engineer Michael O'Shaughnessy.

Design

Strauss was Chief Engineer in charge of overall design and construction of the bridge project. However, because he had little understanding or experience with cable suspension designs, responsibility for much of the engineering and architecture fell on other experts.

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.

Senior engineer Charles Alton Ellis, collaborating remotely with famed bridge designer Leon Moisseiff, was the principal engineer of the project. 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. 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 resonance mode caused by a too-thin roadway and unexpected wind forces.

Ellis was a Greek scholar and mathematician who became a University of Illinois professor of engineering despite having no engineering degree. He became an expert in structural design, writing the standard textbook of the time. Ellis did much of the technical and theoretical work that built the bridge but got none of the credit in his lifetime. In November 1931, Strauss fired Ellis and replaced him with a former subordinate, Clifford Paine, ostensibly for wasting too much money sending telegrams back and forth to Moisseiff. Ellis, obsessed with the project and unable to find work elsewhere during the Depression, continued working 70 hours per week on an unpaid basis, eventually turning in ten volumes of hand calculations.

With an eye toward self-promotion and posterity, Strauss downplayed the contributions of his collaborators who, despite receiving little recognition or compensation, are largely responsible for the final form of the bridge. He succeeded in having himself credited as the person most responsible for the design and vision of the bridge. Only much later were the contributions of the others on the design team properly appreciated. In May 2007, the Golden Gate Bridge district issued a formal report on 70 years of stewardship of the famous bridge and decided to right an old wrong by giving Ellis major credit for the design of the bridge.

Finance

The Golden Gate Bridge and Highway District, authorized by an act of the California Legislature, was incorporated in 1928 as the official entity to design, construct, and finance the Golden Gate Bridge. However, after the Wall Street Crash of 1929, the District was unable to raise the construction funds, so it lobbied for a $35 million bond measure. The bonds were approved in November 1930, by votes in the counties affected by the bridge. The construction budget at the time of approval was $30.1 million. However, the District was unable to sell the bonds until 1932, when the founder of San Francisco–based Bank of America agreed on behalf of his bank to buy the entire issue in order to help the local economy.

Construction

Construction began on 5 January 1933. The project cost more than $26 million.

Strauss remained head of the project, overseeing day-to-day construction and making some groundbreaking contributions. A graduate of the University of Cincinnati, he had placed a brick from his alma mater's demolished McMicken Hall in the south anchorage before the concrete was poured. He innovated the use of movable safety netting beneath the construction site, which saved the lives of many otherwise-unprotected steelworkers. Of eleven men killed from falls during construction, ten were killed (when the bridge was near completion) when the net failed under the stress of a scaffold that had fallen. Nineteen others who were saved by the net over the course of construction became proud members of the (informal) Halfway to Hell Club.

The project was finished by April 1937, $1.3 million under budget.

Opening festivities

The bridge opening celebration began on 27 May, 1937 and lasted for one week. The day before vehicle traffic was allowed, 200,000 people crossed by foot and roller skate. On opening day, Mayor Angelo Rossi and other officials rode the ferry to Marin, then crossed the bridge in a motorcade past three ceremonial "barriers", the last a blockade of beauty queens who required Joseph Strauss to present the bridge to the Highway District before allowing him to pass. An official song, "There's a Silver Moon on the Golden Gate", was chosen to commemorate the event. Strauss wrote a poem that is now on the Golden Gate Bridge entitled "The Mighty Task is Done". The next day, President Roosevelt pushed a button in Washington, DC signaling the official start of vehicle traffic over the Bridge at noon. When the celebration got out of hand, the SFPD had a small riot in the uptown Polk Gulch area. Weeks of civil and cultural activities called "the Fiesta" followed. A statue of Strauss was moved in 1955 to a site near the bridge.

Description

Specifications

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.

Structure

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 State Route 1, and on an average day 118,000 vehicles cross the bridge. The bridge has six total lanes of vehicle traffic and has 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. Although 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 to on 1 October 1983.

Aesthetics

Despite its red appearance, the color of the bridge is officially an orange vermilion called 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 (although Frommers also bestows the "most photographed" honor on Tower Bridge in London, England).

Aesthetics was the foremost reason why the first design of Joseph Strauss was rejected. Upon re-submission of his bridge construction plan, he added details, such as lighting, to outline the bridge's cables and towers.

The Golden Gate Bridge has a similar sister bridge in Lisbon, Portugal. The red-painted Ponte 25 de Abril (25th April Bridge) has a total length of with a central span of .

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. Acrylic topcoats have been used instead since 1990 for air quality reasons. The program was completed in 1995, and there is now maintenance by 38 painters to touch up the paintwork where it becomes seriously eroded.

Current issues

Economics

The last of the construction bonds were retired in 1971, with $35 million in principal and nearly $39 million in interest raised entirely from bridge tolls.

On 2 September 2008, the auto cash toll for southbound motor vehicles was raised from $5 to $6, and the FasTrak toll was increased from $4 to $5. Northbound motor vehicle, bicycle, and pedestrian traffic remains toll free. The rate for two-axle vehicles and motorcycles is $5 cash, or $4 with FasTrak electronic RF payments. For vehicles with more than two axles, the toll rate is $2.50 per axle.

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.

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 Partneship grant. The details of the congestion pricing scheme will be defined before a public hearing scheduled for June 2008, where the board may vote on a proposal to raise the toll to as much as $7 during peak periods. As a condition of the grant, the congestion toll must be in place by September 2009.

Suicides

The Golden Gate Bridge is a frequent site for suicides and is sometimes reported to be the most popular place to commit suicide in the world. The deck is approximately above the water. After a fall of approximately four seconds, jumpers hit the water at some , which is nearly always fatal. Most of those who survive the impact die in the cold water.

There is no accurate figure on the number of suicides 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 , and great white sharks, which tend to congregate around the Farallon Islands, are sometimes seen under the bridge.

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. The count exceeded 1,200 in 2005, and new suicides were averaging one 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. A person jumps off the Golden Gate Bridge every 15 days. An additional 200 may be added to the suicide count on the bridge, because of fog, night-time jumpers, and other jumps that couldn't be counted.

As of 2006, only 26 people are known to have survived the jump. Those who do survive strike the water feet-first usually suffering broken bones and internal injuries. Even when a jumper is promptly rescued from the water and rushed to the hospital, he or she is most likely to die of internal bleeding from ruptured spleens. Another young man survived a jump in 2000, although the impact broke his back and shattered multiple vertebrae. Only one person is known to have made the jump twice—a woman was rescued from the water; hospitalized for her injuries; and, after recovering, jumped again, this time to her death.

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. 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. The estimated cost of a barrier is between $40 and $50 million dollars One recurring proposal is 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). On October 10, 2008, the bridge Board of Directors voted to install a net below the bridge as a suicide barrier.

Wind

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

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 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. The retrofit's planned completion date is 2012.

Notes

References

External links

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