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Golden Gate Bridge

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Golden Gate Bridge
The Golden Gate Bridge is San Francisco’s most prominent landmark, connecting Fort Point in San Francisco to Marin County. The bridge is named after the body of treacherous water over which it crosses known as the Golden Gate Strait. The strait plunges down to a depth of 400 feet (122 m) and was first named “Chrysopylae” by Captain John C. Fremont in 1846, meaning "golden gate."[1]

Officially opened in 1937, the Golden Gate Bridge is 1.7 miles (2.7 km) long with a main suspension span of 4,200 feet (1,280 m),[2] making it the longest suspension bridge in the world for 27 years until the Verrazano-Narrows Bridge in New York Harbor, connecting Brooklyn to Staten Island, was built in 1964 and exceeded it.[3] The Golden Gate Bridge does still hold the record of being the tallest suspension bridge ever erected, with cables, each a yard (0.9 m) thick, suspended from two 746-foot (227.4-m) high towers.[4] Other distinctive features that contribute to the bridge being perhaps the most acclaimed suspension bridge in the world are its art deco design, theatrical lighting, and an uncharacteristic paint color of "vermilion" or "international orange."

The bridge was also constructed to be extremely flexible. It has a 21-foot (6.4-m) sway capacity and a 10-foot (3-m) sag capacity.[5] The bridge can also withstand and support a great deal of weight, even in gale winds.

Today the bridge is maintained by the Golden Gate Bridge and Highway and Transportation District and is the only toll bridge in California that does not fall under state jurisdiction.[6] The $5.00 toll collected from motorists crossing the bridge supports other modes of transportation such as ferries and buses in an effort to minimize traffic over the bridge.

Contents

[edit] Construction History

The construction of the Golden Gate Bridge was sparked by the large-scale engineering achievement of building the Panama Canal. Equally, growth in the western U.S. and the widespread use of the automobile precipitated a demand for projects that improved infrastructure in the 1930s such as tunnels, freeways, and bridges.

[edit] Dream to Bridge the Bay

The concept to build a bridge over the Golden Gate Strait was first thought impossible. An unlikely character named Joshua Norton in 1869, however, brought to light the idea. Norton, a bankrupt Gold Rush merchant who lost his money in a bad investment in the rice market, was regarded in the San Francisco area as a mad man. Declaring himself Norton I, the emperor of the United States, he issued a decree to build a bridge across the bay. His order to build a bridge was considered ludicrous at the time.

In 1872, another man by the name of Charles Crocker, an entrepreneur who had worked on the transcontinental railway that connected California to the eastern seaboard, presented a plan and cost estimate for a bridge spanning the Golden Gate Strait.

Four decades would pass before the scheme of constructing such a monumental bridge would surface again. In 1916, James Wilkins, a structural engineer and newspaper editor for the San Francisco Call Bulletin revisited the concept of a bridge over the Golden Gate Strait. He came up with a design and drummed up public interest by writing about the idea in his newspaper column. His campaign caught the eye of another engineer by the name of Michael M. O’Shaughnessy who consulted other engineers to carry out a feasibility and cost assessment. The engineers estimated a cost of $100 million to build the bridge. A structural engineer by the name of Joseph Strauss proposed that the bridge could in fact be built for somewhere between $25 million to $35 million.[7]

Any effort to build a bridge was postponed by World War I. By 1919, however, public interest in building a bridge across the bay was growing and city officials asked O’Shaughnessy to look into the possibility once more. In 1920, Joseph Strauss submitted a preliminary hybrid cantilever and suspension bridge design that could be constructed at a cost of $27 million.[8] Strauss, though never having worked on a suspension bridge, had worked on a total of 400 bascule bridges.[9] His design for the Golden Gate Bridge was considered unattractive and resembled more of a massive bascule bridge with a suspension span replacing the usual drawbridge or moveable arm. Despite his poor design, city officials were convinced he could build a bridge for a reasonable cost. By 1929, Strauss would become the bridge’s chief engineer.[10]

In 1923, a meeting of representatives from 21 counties was called and the group “Association of Bridging the Gate” was created. The group sought the power to exist as a legal entity and be given the right to organize into a bridge district, borrow money, issue bonds, and construct the bridge and collect tolls. In response to this request, legislation was drafted and the “Golden Gate Bridge and Highway District Act” was passed in May 1923.[11]

The fog rolls into San Francisco

[edit] Opposition to the Bridge

Though public response to the project was positive, there were some who opposed the building of the bridge. Ferry companies saw the bridge as a threat to their economic survival as ferries were the primary means for crossing the strait at the time. An aggressive campaign was launched against the construction of the bridge and formation of a bridge district. The main argument used by the ferry industry was that the 30-minute ride across the strait gave people a break in their day to relax, chat, and mingle. Though the campaign swayed the opinion of some, ferry congestion was becoming increasingly worse and a bridge was seen as the only viable solution to the problem.[12]

The Federal War Department, which owned the land on both sides of the bridge's prospective location, expressed doubts. They wanted to ensure that a bridge would not hinder navigation. There was also a concern as to whether or not adequate financing was available for the bridge’s construction. A meeting was held in the spring of 1924 to discuss these two concerns and after a convincing case was made, a provisional permit was issued.[13]

[edit] A Golden Opportunity: Financing the Bridge

Financing the bridge at the cusp of the Great Depression proved to be difficult but many people believed in the bridge’s potential to pull them out of economic depression. As a result, the Golden Gate Bridge was the first bridge to be financed entirely by private citizens. In an unprecedented vote for a bond issue of $35 million to pay for the bridge’s construction, 145,697 people approved and 47,005 opposed.[14] Those who voted in favor were willing to put up their homes, farms, and businesses as collateral.[15]

The formula for financing the bridge was quite successful too. Those who contributed funds were promised restitution at 4.75 percent interest rate within a maximum of 40 years.[16] The last of these construction bonds would be retired as late as 1971. In total, bridge tolls would finance the $35 million in principal it cost to build the bridge and nearly $39 million in interest.[17]

[edit] Bridge Design and Aesthetic Appeal

Strauss eventually abandoned his hybrid cantilever and suspension bridge design, opting for an all-out suspension bridge design instead. To define the bridge’s design, he enlisted the assistance of Charles Ellis, a former professor of structural and bridge engineering at the University of Illinois, to draw up new plans. Ellis would make detailed calculations with concern to major bridge components such as suspension ropes, decks, floor beams, highway track, cables, bridges, and towers, and more in addition to writing the specifications for all 10 of the bridge’s construction contracts.[18] Strauss eventually became impatient with how long it was taking Ellis to make all the necessary calculations. He replaced him with a man named Clifford Pain and removed the mention of Ellis’s name from all the bridge materials he had worked on.

Leon S. Moisseiff, designer of the Manhattan Bridge over the East River in New York and the Philadelphia-Camden Bridge, built in 1926, was also hired to work with Strauss. Moisseiff was an expert in wind stresses on bridges. He showed that the main bridge cables could absorb as much as half the wind pressure and transmit it to the bridge towers and abutments. With suspenders properly adjusted, the bridge would be flexible enough to bend and sway in high winds. The bridge’s two towers were reminiscent of the towers on Moisseiff’s Philadelphia-Camden bridge that featured large steel-cell cross members, each set within a rectangle.[19]

A local architect by the name of Irving Morrow was hired to address the bridge’s architectural treatment. He would later be credited for the bridge’s art deco theme, lighting, and unique orange-vermilion color called “international airway orange.” Instead of choosing a conventional black, gray, or silver color, Morrow felt the orange color blended better with the surrounding natural landscape. It would also give the bridge greater visibility to passing ships.[20]

[edit] Building the World’s Biggest Bridge

In November 1932, a total $23,844 million in contracts was awarded.[21] The largest of these contracts went to McClinitic-Marshall Corp., who put in a bid on the steel superstructure. John A. Roebling Sons was awarded the contract for cabling. The Pacific Bridge Co. was awarded the contract for constructing the bridge’s two towers.[22] Construction finally commenced on the bridge on January 3, 1933.

[edit] Anchorages

Workers started with blasting and excavating 3.25 million cubic feet (92,030 m3) of dirt on both sides of the strait to support the huge anchorages and pylons that were massive blocks essentially used to grip the bridge’s two supporting cables.[23] Each anchorage was 150 feet (46 m) long and weighed approximately 60,000 tons and had to have enough strength to resist a cable pull of 62 million pounds (28 million kg).[24] By February 1933, both of the anchorages were completed and construction on the North and South Pier began.

[edit] North Pier

The North Pier on the Marin County shore was relatively easy to build in comparison to the South Pier on the San Francisco side. The North Pier was built into the bedrock only 20 feet (6.1 m) below the water and the tower was build on land.[25]

[edit] South Pier

The South Pier, built on an uneven sloping rock floor on the San Francisco side, was the most difficult part of the bridge’s construction. The South Pier had to be built 1,200 feet (366 m) from the shore and 100 feet (30.5 m) below the ocean’s surface. This proved to be quite a feat given that strong gales, tides, and fog caused substantial delays.[26]

The problem was resolved by first blasting away rock picked up by dredgers in order to level the ocean floor. A huge 750-foot (229-m) cofferdam or fender was then constructed to diminish tidal action and waves and facilitate construction of the South Pier.[27] Heavy steel boxes were bolted to the bottom of the fender by divers and then filled with concrete until the fender sat 15 feet (4.6 m) above sea level.[28] Approximately 152,600 tons of concrete went into the construction of the concrete fender that was 300 feet (91 m) long and 155 feet (47.2 m) wide at the center of the bridge -- almost the size of a football field by today’s standards.[29] The fender itself would become part of the bridge’s actual foundation with the pier being built inside the fender.

[edit] Towers

Looking up at one of the towers
Each tower was composed of thousands of pieces of fabricated steel. The steel was fabricated in Bethlehem, Pennsylvania. Shipping the pieces of fabricated steel to the construction site was a time-consuming process. The shipments were sent by rail to East Coast seaports where they were loaded and shipped via the Panama Canal to McClintic-Marshall Corp.’s storage yards in Alameda. From there, shipments were taken by barge across the bay to the construction site. The steel pieces or girders were hoisted into position by giant cranes. Workers then bonded the sections together with rivets and hot steel.[30]

[edit] Cable Spinning

The bridge was built using the loom-type spinning carriages provided by Roebling. No derrick existed at the time that could lift the cables as heavy as the ones being used on the bridge. Instead, the cables had to be spun on-site from the anchorages in Marin and San Francisco. These spinning carriages moved at 650 feet (198 m) per minute and carried 27,572 pencil thick wires along at a length of 7,650 feet (2,332 m). Each cable was compressed to a diameter of 36 inches (91 cm) and hung with wire ropes to hold the roadway.[31]

A total of 80,000 miles (128,848 km) worth of wire was used in the two cables with each cable consisting of 25,0000 compacted into 122 strands,[32] which is enough to circle the equator three times.[33] Completed by 1936, it took six months to spin the suspension cables.

[edit] Roadway

The roadway across the bridge was fabricated from steel and concrete. Working from each tower, traveling cranes first laid down the steel decking that would form the roadway, after which concrete was poured over top.

[edit] Construction Safety

Strauss was a huge advocate of taking safety precautions and imposed some of the most rigorous safety measures in the history of bridge building. Up until the construction of the Golden Gate Bridge, it was estimated that one man would easily die for every $1 million spent to build a bridge.[34] The construction of the Golden Gate Bridge shattered that record. Strauss made workers wear protective headgear designed by local manufacturer named Edward W. Bullard. The company got its start providing headgear for miners and then the construction industry. In 1919, Bullard manufactured the “Hard Boiled Hat,” considered the very first hard hat.[35]

Secondly, Strauss insisted on the placement of a huge safety net that spanned the entire underside of the bridge. The net cost $130,000 and was suspended 60 feet (18.3 m) below the workers.[36] The net would save the lives of 19 men who became known as the “Halfway-to-Hell Club.” [37]In total, 11 men died during the bridge’s construction. On February 17, 1937 there was a tragic accident when a section of scaffolding gave way and 12 men plummeted into the waters below with only two surviving the fall.

[edit] Golden Gate Bridge’s Grand Opening

The Golden Gate Bridge officially opened on May 27, 1937 with then-president Theodore Roosevelt sending out a telegram to the world announcing the bridge’s completion. The bridge’s opening day would become known as Pedestrian Day with over 200,000 people crossing over the bridge by foot to take in its aesthetic and technological wonder.[38] On May 28, 1937, the bridge was opened to vehicular traffic. By midnight, over 32,000 vehicles and 19,350 pedestrians had paid the 50-cent toll to cross the bridge.[39]

The opening of the Golden Gate bridge extended into a week-long party that included a nightly pageant at Crissy Field, fireworks, parades, tournaments, and local entertainment. The sound of car horns, sirens, cannons, bells, and whistles filled the air. A total of 400 Navy biplanes, 19 battleships and heavy cruisers, three carriers, and other ships sailed into the San Francisco Bay to herald the bridge’s completion.[40]

[edit] Equipment Used

[edit] Refurbishment/Recent Projects/Renovations

A number of refurbishment projects have been undertaken to maintain the bridge’s structural integrity and general appearance. Today, a total of 17 ironworkers and 38 painters are employed to carry out maintenance on the bridge.[41] The ironworkers replace corroding steel and rivets with high-strength steel bolts. Also, they assist painters with rigging as well as removing plates and bars to provide better access to the bridge’s interior columns and chords when they need to be painted.

[edit] Painting

In 1965, the bridge was starting to corrode and a program was implemented to remove the lead-based paint originally used. Removal of the original paint took over 30 years to complete and was replaced with an inorganic zinc primer and acrylic emulsion topcoat. During the 1980’s, a water-borne inorganic zinc primer and an acrylic topcoat replaced the paint again. Today, painting the bridge is an ongoing task.

[edit] Bridge Deck

Over the years salt has contributed to the deterioration of the original bridge deck, leading to some major refurbishment projects. In 1953, the bridge deck was stiffened with lateral and steel bracing. In 1985, the bridge’s entire deck was resurfaced with a lighter, stronger material that reduced stress placed on the cables and anchorages. The latter project cost an estimated $52.5 million[42]—more than the cost of the bridge’s initial construction back in 1937.

[edit] Earthquake Retrofitting

While it took four years to build the Golden Gate Bridge, seismic engineers anticipate a devastating earthquake could bring down the bridge in less than 60 seconds.[43] Even a mild earthquake could cause irreparable damage that would result in the bridge’s closure.

Seismic engineers are convinced a complete retrofit of the bridge at a cost of $175 million is required to make the bridge earthquake proof. In fact, new supercomputers are being used to simulate the effect an earthquake would have on each part of the bridge. The project will take a total of five years and represents only about one-tenth of the actual $1.4 billion replacement cost of the bridge.[44] The retrofit is designed to limit the amount of violent action likely to be caused by excessive ground motion. This will involve strengthening several areas of the bridge including work on the structural steel, approach, viaducts, concrete piers, pylons, and anchorage housings.

[edit] Unique Facts

  • January 3, 1933 - Construction on the Golden Gate begins
  • May 27, 1937 - Golden Gate opens to pedestrian traffic
  • May 28, 1937 - Golden Gate opens to vehicular traffic
  • As of June 2005 1,799, 032, 891 vehicles had crossed the bridge.
  • Almost 1.5 million people have crossed the bridge since it opened.
  • The toll has increased from 50 cents to $5.00 dollars over the years.
  • Eleven men died in the construction of the bridge.
  • The bridge was built in four years and completed five months behind schedule.
  • The final cost of the bridge was $27 million—$1.3 million under budget.
  • Replacement cost for the bridge today is about $1.4 billion dollars.

[edit] Bridge

  • Bridge span: 4,200 feet (1,280 m)
  • Deck length: 1.7 miles (2.7 km)
  • Bridge width: 90 feet (27.4 m)
  • Sidewalk width: 10.5 feet (3.2 m)
  • Bridge weight when built: 894,500 tons
  • Bridge weight as of 1994: 887,000 tons

[edit] Towers

  • Tower height above water: 746 feet (227.4 m)
  • Tower height above roadway: 500 feet (152.4 m)
  • Weight of two tower: 44,000 tons
  • Each tower has 600,000 rivets

[edit] Cables

  • Length of each cable: 7,650 feet (2,332 m)
  • Number of wires in each cable: 27,572
  • Total length of wire used: 80,000 miles (128,748 km)

[edit] References

  1. Malloy, Betsy. Golden Gate Bridge Facts. About.com, 2008-09-23.
  2. iNeTours.com San Francisco's Golden Gate Bridge, Pictures and History, 2008-09-23.
  3. Elliott, Kathleen. Golden Gate Bridge Changes Engineers' Reasoning. California Historian, 2008-09-23.
  4. iNeTours.com San Francisco's Golden Gate Bridge, Pictures and History, 2008-09-23.
  5. Baylink. Golden Gate Bridge, 2008-09-23.
  6. Baylink. Golden Gate Bridge, 2008-09-23.
  7. PBS. Golden Gate Bridge: Bridge Facts, April 2004. (accessed: 2008-09-23)
  8. History.com This Day in History: May 27, 1937, 2008-09-23.
  9. Sigmund, Pete. The Golden Gate: 'The Bridge That Couldn't Be Built'. Construction Equipment Guide, June, 2006. (accessed: 2008-09-23.)
  10. History.com This Day in History: May 27, 1937, 2008-09-23.
  11. PBS. Golden Gate Bridge: Timeline, April 2004. (accessed: 2008-09-23)
  12. Elliott, Kathleen. Golden Gate Bridge Changes Engineers' Reasoning. California Historian, 2008-09-23.
  13. Elliott, Kathleen. Golden Gate Bridge Changes Engineers' Reasoning. California Historian, 2008-09-23.
  14. Elliott, Kathleen. Golden Gate Bridge Changes Engineers' Reasoning. California Historian, 2008-09-23.
  15. PBS. Golden Gate Bridge: Timeline, April 2004. (accessed 2008-09-23)
  16. Elliott, Kathleen. Golden Gate Bridge Changes Engineers' Reasoning. California Historian, 2008-09-23.
  17. PBS. Golden Gate Bridge: Timeline, April 2004. (accessed: 2008-09-23)
  18. Sigmund, Pete. The Golden Gate: 'The Bridge That Couldn't Be Built'. Construction Equipment Guide, June, 2006. (accessed: 2008-09-23)
  19. Sigmund, Pete. The Golden Gate: 'The Bridge That Couldn't Be Built'. Construction Equipment Guide, June, 2006. (accessed: 2008-09-23)
  20. Sigmund, Pete. The Golden Gate: 'The Bridge That Couldn't Be Built'. Construction Equipment Guide, June, 2006. (accessed: 2008-09-23)
  21. PBS. Golden Gate Bridge: Timeline, April 2004. (accessed: 2008-09-23)
  22. Sigmund, Pete. The Golden Gate: 'The Bridge That Couldn't Be Built'. Construction Equipment Guide, June, 2006. (accessed: 2008-09-23)
  23. PBS. Golden Gate Bridge: Timeline, April 2004. (accessed: 2008-09-23)
  24. Great Buildings Online. Building the Golden Gate Bridge, 1933-1937, 2008-09-23.
  25. PBS. Wonders of the World Databank: Golden Gate Bridge, 2008-09-23.
  26. Baylink. Golden Gate Bridge, 2008-09-23.
  27. Baylink. Golden Gate Bridge, 2008-09-23.
  28. Baylink. Golden Gate Bridge, 2008-09-23.
  29. Associated Oil Company. Colossus of the Pacific. The Virtual Museum of the City of San Francisco, 2008-09-23.
  30. Bridge. Lib. Berkeley. 2008-11-03.
  31. Great Buildings Online. Building the Golden Gate Bridge, 1933-1937, 2008-09-23.
  32. Sigmund, Pete. The Golden Gate: 'The Bridge That Couldn't Be Built'. Construction Equipment Guide, June, 2006. (accessed: 2008-09-23)
  33. Essortment.com Golden Gate Bridge: history and information, 2008-09-23.
  34. Malloy, Betsy. Golden Gate Bridge Facts. About.com, 2008-09-23.
  35. GoldenGateBridge.org FAQs: Were Hard Hats Used During Construction?, 2008-09-23.
  36. PBS. Golden Gate Bridge: Timeline, April 2004. (accessed: 2008-09-23)
  37. Elliott, Kathleen. Golden Gate Bridge Changes Engineers' Reasoning. California Historian, 2008-09-23.
  38. Bridge. Lib Berkeley. 2008-11-03.
  39. PBS. Golden Gate Bridge: Timeline, April 2004. (accessed: 2008-09-23)
  40. Sigmund, Pete. The Golden Gate: 'The Bridge That Couldn't Be Built'. Construction Equipment Guide, June, 2006. (accessed: 2008-09-23)
  41. GoldenGateBridge.org FAQs: How Often is the Golden Gate Bridge Painted?, 2008-09-23.
  42. Corrosion-Doctors.org Golden Gate Bridge, 2008-09-23.
  43. McGraw, Marcus. Golden Gate Bridge Opens: May 27, 1937. FactMonster.com, 2008-09-23.
  44. Golden Gate. Info Please. 2008-11-03.