Golden Gate Bridge
Coordinates: 37 ° 49 ′ 3 " N , 122 ° 28 ′ 42" W.
| Golden Gate Bridge | ||
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| Official name | Golden Gate Bridge | |
| use | Motor vehicles: US Highway 101 , California State Route 1 (6 lanes), pedestrians, bicycles | |
| Crossing of | Golden gate | |
| place | San Francisco ( California ) and Marin County ( California ) | |
| construction | Suspension bridge | |
| overall length | 2737 m | |
| width | 27 m | |
| Longest span | 1280 m | |
| height | 227 m | |
| Headroom | 67 m at high tide | |
| vehicles per day | 120,000 vehicles | |
| building-costs | 35 million USD (adjusted for inflation in 2013 about 629 million USD) | |
| start of building | January 5, 1933 | |
| completion | April 19, 1937 | |
| opening | 27./28. May 1937 | |
| planner |
Joseph B. Strauss , Charles A. Ellis, Irving F. Morrow (architect) |
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| toll | Direction of travel towards the city | |
| location | ||
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The Golden Gate Bridge ( English for bridge over the golden gate ) is a suspension bridge at the entrance to San Francisco Bay over the Golden Gate in California . It is the symbol of the entire Bay Area and for many a symbol of the United States, along with the New York Statue of Liberty . It is also one of the most important attractions in San Francisco . The Golden Gate Bridge was added to the List of Historic Civil Engineering Landmarks by the American Society of Civil Engineers in 1984 and declared one of the modern wonders of the world in 1995 .
The building was opened in 1937, has a clearance height of 67 meters at high tide and, with its six lanes and two footpaths and bike paths, connects San Francisco with Marin County and the less densely populated Napa and Sonoma Valley. A segment of the approach to the bridge, optically designed as an arch bridge, spans Fort Point on the city side .
construction
When it opened, the Golden Gate Bridge was the longest suspension bridge in the world with a main span of 1,280 meters . It was not replaced by the Verrazzano-Narrows Bridge until 27 years later in 1964 , but it is still one of the longest suspension bridges in the world. The entire bridge, including the access bridges, is 2737 meters long. The actual suspension bridge has a total span of 1966 meters and has pylons 227 meters high . The pylon stems are made of steel and are three times thick. At each graduation they are connected to each other by crossbars. The heights of the steps and the crossbars decrease towards the top. The 27.4 meter wide roadway girder consists of 7.6 meter high lattice girders in the longitudinal direction, which are connected to one another by horizontal associations. The two cables have a diameter of 0.92 meters each and the hangers are attached to them at intervals of 15 meters.
construction of the bridge
prehistory
Initial plans to bridge the bay were dated back in 1872, but the obvious difficulties - open sea, deep water, strong tidal currents, fog, storms and earthquake risks - raised concerns about whether the bridge was possible and affordable.
In response to a request from the San Francisco City Council in 1921 , Joseph B. Strauss submitted plans for a combined cantilever and suspension bridge with a span of 1,222 meters, which, however, was rejected because of its appearance, apart from the financing problems. When the ferries reached their capacity limits, the bridge project was vigorously pursued. In 1924, the War Department, as the owner of the land on both sides of the Golden Gate, issued a preliminary permit, which met with fierce opposition, including from the ferry companies, and led to eight years of bitter legal disputes.
In January 1929, the "Golden Gate Bridge, Highway and Transportation District", a special-purpose district founded for bridge construction and administration , began its work. Joseph B. Strauss was appointed Chief Engineer , and his associates Charles A. Ellis and Clifford E. Paine were hired as Vice-Presidents . In addition, an expert advisory board was formed, which included the well-known bridge engineers Leon S. Moisseiff , Othmar Ammann and Charles Derleth, Jr. from the University of California, Berkeley and the architect Irving F. Morrow, who designed the outer shape of the pylons.
Meanwhile had in progress steel - production and applied on hanging bridges of Moisseiff and advanced Deflektionstheorie make obsolete the original plans for the bridge. Moisseiff had advised Strauss to use a suspension bridge as early as 1925. With the George Washington Bridge , built from 1927 to 1931, Othmar Ammann showed that suspension bridges with such spans are possible. For this reason, between 1925 and 1929, Strauss changed his plans for the bridge to a pure suspension bridge with a span of 1,280 meters - the longest suspension bridge in the world.
In October 1929, the great stock market crash that started the Great Depression took place . Nevertheless, after violent public disputes in November 1930, it was possible to secure the financing of the bridge construction through loans in the amount of 35,000,000 US dollars. The bridge was financed with these bonds alone. The repayment of the capital of 35 million US dollars and the total accrued interest of 39 million US dollars were paid from the toll income , and in 1971 the last bond was redeemed. Only Sausalito's side driveway, now known as Alexander Avenue, was built with the help of the Works Progress Administration program, a job creation agency established by President Roosevelt as part of the New Deal . Due to further legal proceedings, the start of construction had to be postponed again.
In the meantime, Strauss and his engineering office were working intensively on the planning of the bridge. Charles A. Ellis led the preparation of thousands of calculations, the preparation of the execution plans, the specifications and the tender documents in the Chicago office. He often consulted by telegram and telephone with Moisseiff in New York , who was asked for advice on practically all suspension bridges of that time, including Ammann's George Washington Bridge, but also sought Ammann's opinion. Ellis was working tirelessly on the daunting task when Strauss insisted on December 5, 1931 that he take leave. Three days before the end of this vacation, Ellis received a letter in which Strauss asked him to hand over his documents to his deputy and to take an indefinite vacation. It has never been clarified what prompted Strauss to take this step. It is often assumed that Strauss did not want his role as the creator of this huge structure to be compromised.
construction
On January 5, 1933, the start of construction was celebrated with events on both sides of the strait.
The construction was an enormous technical challenge. The bridge broke many records: the highest piers at 227 meters, the longest (2332 meters) and thickest (92 centimeters) cable strands and the largest underwater foundations. These foundations also had to be lowered into a strait shaped by strong currents.
The northern pylon was erected directly on the rocky shore, so the concrete foundations could be completed in a few months without any problems. The ten-story high foundations of the southern pylon, on the other hand , were built in deep water about 340 meters from Fort Point . The temporary bridge set up for this purpose was destroyed by a ship and damaged several times by high waves in heavy storms, so that the construction of these foundations took two years.
The construction of the steel towers and the steel bridge deck had been awarded to the McClintic-Marshall Company , which was taken over by Bethlehem Steel in 1931 . The individual parts were manufactured in Pittsburgh , Pennsylvania , provisionally assembled for inspection, dismantled again and taken by rail to Philadelphia . There they were loaded onto the ships of the Group's own shipping company Calmar Line , which drove them over a distance of almost 10,000 kilometers through the Panama Canal to the storage area in Alameda in the Bay of San Francisco. The individual parts were then brought to the bridge by barge. Cranes were mounted between the two towers of the pylons, which climbed up the parts that had just been completed in 12-meter sections.
As with many other suspension bridges, John A. Roebling's Sons Co. was commissioned to install the suspension cables and hangers . The first thin rope was pulled by boat across the strait, which was closed to shipping. This rope was used to pull a number of stronger ropes over, which were used to install the catwalks reaching from one anchor block via the cable saddles on the pylon tops to the anchor block opposite . The wheels ran back and forth on ropes above the catwalks, pulling the individual galvanized wires for the suspension cables from anchor block to anchor block using the air-jet process . For each suspension cable, 27572 wires had to be pulled over the pylons in this way, which were bundled into bundles, aligned next to one another and formed into a round parallel wire rope with a diameter of 92 centimeters by rope presses . Then they were sheathed with a thin wire to prevent corrosion. The air-jet spinning process for both suspension cables took six months and nine days. With that Roebling's Sons. Co. improved this process by 60% compared to the construction of the George Washington Bridge. The 250 pairs of hangers were then hung over the suspension cables at a distance of 15 meters each, to which the roadway girder was finally attached.
The assembly of the deck girder began on the pylons and ended in the middle of the bridge. With this method, the carriageways initially protrude comparatively steeply upwards, before they slowly lowered with the progressive assembly and the load on the central areas of the suspension cables and finally met in the middle on November 20, 1936. The two 7.6 meter high lattice girders arranged on the outside and used for stiffening were originally only connected to each other in the upper area by horizontal associations.
The work was completed on April 19, 1937 - a little ahead of the agreed time and just below budget. The bridge was opened to road traffic on May 28, 1937 at noon by a telegraph signal from President Franklin D. Roosevelt from the White House. At the opening, a chain was cut instead of the usual ribbon. The day before, the bridge had already been opened to pedestrians and 200,000 people took the opportunity to take a walk.
The structure weighs a total of 887,000 tons. Approx. 600,000 rivets hold each of the two towers together.
Half-way-to-hell club
In order to reduce the number of accidents considered inevitable, Joseph B. Strauss had given strict instructions for the first time that protective helmets had to be worn and that a safety net had to be installed to catch falling construction workers before a new carrier section was installed. This network saved the lives of nineteen workers during the construction phase, including Alfred Zampa . This group of survivors came to be known as the "Half-Way-to-Hell-Club". By the end of January 1937, one person died during the construction work. On February 17, 1937, a piece of scaffolding occupied by twelve people fell into the net, which could not withstand the force, and ten workers fell to their deaths. There were thus a total of eleven deaths, while it was assumed that for every million dollars in construction costs one worker, or 35 lives, would be lost.
Origin of name
The bridge was named after the natural entrance to the Bay of San Francisco. This entrance (the Golden Gate) is 1.6 kilometers wide. The bay entrance was named Golden Gate or Chrysopylae from Captain John C. Frémont around 1848 during the gold rush in California , to whom the Strait of the Sea was reminiscent of the Golden Horn (Greek Chrysoceras ) in Constantinople , now Istanbul.
traffic
Around 120,000 vehicles drive on the bridge every day . The journey northwards out of the city is free of charge for all vehicles, the return journey into the city is subject to a toll. Vehicles with an electronic identification and payment system called FasTrak (1) pay a lower amount. Cyclists and pedestrians do not have to pay any toll. During the two daily peak times, vehicles with at least three passengers also drive toll-free. The constantly adjusted toll revenues have been covering the maintenance costs for decades, although large sums have to be raised to protect the non-rusting metal structure from the salty air, in contrast to the San Francisco-Oakland Bay Bridge .
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Of the six lanes, four inward and two out of town are open during the morning rush hour on weekdays. Outside this time, traffic travels on three lanes in both directions. Until January 2015, the lanes leading out of town and in town were separated from each other by yellow plastic pipes. These plastic pipes were repositioned by hand twice a day. Because these slight road separations could not prevent breakthroughs, there were 128 frontal collisions between 1970 and 2015. To increase traffic safety on the bridge, an adjustable middle plank system ( Moveable Median Barrier System ) was installed on January 9 and 10, 2015 . Since then, the two directions of travel have been separated by 3,500 steel elements with concrete filling connected with steel pins, these are shifted twice a day by a special vehicle driving along. As part of the installation of the new $ 30 million system, the bridge was completely closed to car traffic for the first time since 1987. This closure was also the longest in the history of the Golden Gate Bridge.
Paint and painting
According to planning by the civil engineer Joseph B. Strauss, the bridge should be painted an ordinary gray. The orange used is actually a protective agent and is called the International Orange . It almost turned gray like most other bridges, or black with yellow stripes if the Navy had their way. But the orange of the anti-rust color appealed to the residents of San Francisco, and since this earthy shade of orange also looked good against the backdrop of the surrounding hills and mountains and the bridge thus blended well into the landscape, Joseph B. Strauss decided on the color of the bridge to leave that way.
Renewing the paint is a recurring job and the main activity in maintaining the bridge. The paint protects the steel components from corrosion. There is a lot of misunderstanding about how often the bridge is painted. Some report a complete repaint in seven years, others say it happens once a year. In reality, the bridge was equipped with a red lead during construction . For the next 27 years only repairs had to take place. In 1968 the corrosion had progressed so far that the old paint was removed and replaced by an inorganic zinc-silicate adhesion promoter with a plastic component in the top coat. The top coat was replaced with an acrylic emulsion in 1990 to meet air standards for volatile organic compounds . The program was successfully completed in 1995 with a focus on the areas of greatest corrosion.
Major maintenance work on the bridge
Only three years after the Golden Gate Bridge, the Tacoma Narrows Bridge had been completed, a shorter, but significantly slimmer bridge with only two lanes, which used very low solid steel girders instead of high lattice girders . Its collapse, caused by vibrations, in 1940 meant that greater demands were placed on the rigidity of a bridge girder. The Golden Gate Bridge, with its significantly better stiffness values, did not seem to be affected. In 1951, an exceptionally strong storm also raised her concerns. Therefore, from 1953 to 1954, their trusses were stiffened by lower horizontal cross braces.
Between 1973 and 1976 all hangers were replaced. From 1980 to 1982 measures to increase earthquake security were carried out. The concrete pavement was then removed while traffic was running, the upper steel girders were replaced by orthotropic plates and a new, thin pavement was applied. This measure, which was completed in 1986, was able to reduce the mass of the bridge by 11,000 tons.
The Loma Prieta earthquake of October 17, 1989 did not cause any significant damage to the bridge, but in the 1990s it led to static investigations and subsequent reinforcement measures, which were ended in 2008. Among other things, vibration dampers were installed and the pillar foundations reinforced.
Bridge anniversary 1987
For the anniversary of the bridge, when it was closed to traffic, around 300,000 visitors were on the bridge at the same time on May 24, 1987 (a Sunday). Another 500,000 or so were waiting at their ends. The pavement dropped up to 7 feet in the middle. Further access was blocked. According to a later legend, there was a risk of collapse, and so immediately afterwards said the politician responsible for the district Gary Giacomini. According to the engineers of the bridge, this danger never existed. The bridge was designed to withstand a live load of 4,000 pounds per foot, which increased to 5,700 pounds after the bridge was overhauled (lighter steel structure) in the mid-1980s. However, even when they were almost shoulder to shoulder, the pedestrians only represented a load of around 5400 pounds (about twice as much as a traffic jam). Also, the bridge is designed to have a safety factor of at least 1.5, and it is not uncommon for suspension bridges of this size to move the pavement up to 10 feet (the design should vary up to 16 feet vertically and 27 feet horizontally withstand without permanent damage). A repetition of the unlimited opening for pedestrians is excluded for other reasons such as a possible panic. On the anniversary day, there came a critical point when the streams of visitors from both sides met in the middle and people realized that they could no longer move forwards or backwards. They also found that the bridge moved naturally in the wind blowing around 40 mph, which made some people uncomfortable.
Suicides
The Golden Gate Bridge is often used by people to kill themselves by jumping. Since the bridge was opened in 1937, it is estimated that up to 2013 more than 1,600 people have died jumping over the railing, which is only 1.20 meters high. There have been several discussions in the American media about whether it is not possible to erect a barrier that would at least make suicide more difficult , as is the case with other tall structures, but this was repeatedly rejected by the responsible authorities because it was assumed that there was a risk of suicide People would then seek another location to attempt suicide. In the meantime, however, it has been proven that suicides jumping from bridges are so-called impulse suicides . The majority (> 90 percent) of these do not make a second attempt later if they were prevented from jumping the first time. The construction of a barrier failed due to the difficult financial situation of the operating company (the fence would cost around 50 million dollars) and aesthetic concerns. In 2018, the construction of protective nets began, which should protrude six meters on both sides. The cost of the installation, which is to take three years, amounts to the equivalent of around 180 million euros.
Several telephones are attached to enable a suicidal person to contact professional help. Telephone calls are difficult or impossible in practice due to the noise from traffic and the often violent wind noise.
Most suicidal jumps take place on the bay-facing side. The side facing the Pacific is not open to pedestrians.
Suicide on the Golden Gate Bridge is the subject of Jenni Olson's experimental film The Joy of Life (2005) and the film The Bridge , released by documentary filmmaker Eric Steel in 2006 . The song "Jumpers" by the American rock band Sleater-Kinney also addresses the frequent suicides , released in 2005 on the album "The Woods" and as a single.
Web links
- Official website (English)
- Golden Gate Bridge. In: Structurae
- Golden Gate Bridge - Virtual Tour (English)
- Golden Gate Bridge - at brueckenweb.de
- West Coast USA: Golden Gate Bridge Interesting facts about the Golden Gate Bridge
Individual evidence
- ↑ goldengatebridge.org
- ^ Bridge Design and Construction Statistics on the Golden Gate Bridge website
- ↑ Concept for a Bridge Across the Golden Gate Strait on the Golden Gate Bridge website
- ^ Special District Formed - Golden Gate Bridge and Highway District on the Golden Gate Bridge website
- ↑ a b Golden Gate Bridge Design on the Golden Gate Bridge website
- ↑ Bond Measure Passes on the Golden Gate Bridge website
- ^ The Bridge Builders KPIX documentary on the San Francisco Bay Area Television Archive
- ↑ Richard Scott: In the wake of Tacoma, suspension bridges and the quest for aerodynamic stability. ASCE Press, Reston, Va. 2001, ISBN 0-7844-0542-5 , p. 27
- ↑ Barbara Munker: 75 years of the Golden Gate Bridge: Sun salutation on the bridge pillar . In: Spiegel Online , April 28, 2012
- ^ LIFE on the American Newsfront: Ten Men Fall to Death on Golden Gate Bridge. In: LIFE, edition March 1, 1937, p. 20 . Retrieved January 18, 2014.
- ↑ a b c Golden Gate Bridge closing to install new collision barrier , CBS News January 9, 2015, last accessed January 10, 2015.
- ↑ Citylab: It's Time to Reverse Our Thinking on Reversible Lanes , March 19, 2015
- ^ Painting the Golden Gate Bridge. Golden Gate Bridge, Highway and Transportation District. Retrieved November 25, 2016 .
- ↑ Stephen Tung, The day the Golden Gate Bridge flattened , Mercury News, May 23, 2012
- ↑ a b Stephanie Smith: Funding for Golden Gate Bridge suicide barrier approved. In: CNN . June 30, 2014. Retrieved June 28, 2014.
- ↑ R. Seiden: Suicide and Life Threatening Behavior , Vol. 8 (4), Winter 1978, Human Sciences Press (PDF)
- ↑ Golden Gate Bridge receives protective device for tiredness of life . In: The world . June 28, 2014. Retrieved July 29, 2014.
- ↑ Home | Golden Gate Bridge. Retrieved September 16, 2019 .
- ^ Golden Gate Bridge, Bikes . Website of the Golden Gate Bridge operating company. Retrieved October 17, 2009.