Golden Gate Bridge

INTRODUCTION
The Golden Gate Bridge is recognized by the American Society of Civil Engineers as one of the 7 civil engineering wonders of the world. When it opened in 1937, the bridge had the longest main span of any suspension bridge in existence. It held that record until the Verrazano-Narrows Bridge was completed in 1964.
The Golden Gate Bridge links San Francisco with California’s Marin County. It spans the Golden Gate Strait (which is a narrow water passage) between San Francisco Bay and the Paacific Ocean.
Work on the Golden Gate Bridge began in 1933. Building the bridge was difficult and dangerous. The Golden Gate Strait is swept by 60-mile-per-hour winds, fierce ocean currents and tides, and for much of the year, the bridge is shrouded in thick fog.
The bridge was designed as a “bending bridge,” capable of 21-foot sway and a 10-foot sag. It was built to withstand winds of up to 100 miles-per-hour as well as the earthquakes that threaten the area.
Workers who had too climb to great heights were put on special diets to prevent dizziness. A huge safety net was slung beneath the bridge. It saved the lives of 19 workers who fell off the bridge. In February 1937, disaster struck! A scaffold gave wa

ay and broke through the net, killing 10 men.
Work on the 5-lane Golden Gate Bridge continues. They have replaced much of the pedestrian hand railing and are now working to strengthen the bridge against earthquakes.
Golden Gate Bridge History
For many years before the Golden Gate Bridge was built, the only way to get across San Francisco Bay was by ferry, and by the early twentieth century the Bay was clogged with ferries. In the 1920s, engineer and bridge-builder Joseph Strauss became convinced that a bridge should be constructed across the Golden Gate.
Many groups opposed him, each for their own selfish reasons: the military, loggers, the railroads. The engineering challenge was also enormous – the Golden Gate Bridge area has winds of up too 60 miles per hour, and strong ocean currents sweep through a rugged canyon below the surface. If all that weren’t enough, it was the middle of the Great Depression, funds were scarce, and the San Francisco Bay Bridge was already under construction. In spite of everything, Strauss persisted, and San Francisco voters overwhelmingly approved $35 million in bonds to construct the Golden Gate Bridge.
The now-familiar art deco Golden Gate Bridge design and International Red color were chosen, and construction began in 19
933. The Golden Gate Bridge project was completed in 1937. Strauss was a pioneer in building safety, with innovations including hard hats and daily sobriety tests. The Bay Bridge (which was being built at the same time) lost 24 lives while the Golden Gate Bridge lost only 12, an outstanding accomplishment in an era when one man was killed on most construction projects for every million spent.
DESIGN AND CONSTRUCTION
Political and legal delays resulted in nearly a decade between Joseph Strauss’ first design proposal for the Golden Gate Bridge — an unsightly railroad trestle that would have blocked views and sunsets — and his appointment to serve as chief engineer. His associates on the project included resident engineer Russell Cone, consultants O.H. Ammann and Leon Moisseiff, University of California, Berkeley professor of engineering Charles Derleth, Jr., and retired UC geology professor Andrew C. Lawson.
But it was chief assistant engineer Clifford Paine and architect Irving Morrow who actually deserve credit for the design and construction of the bridge that stands today. Morrow designed the towers with a subtlety of ornamentation and an understanding of height and perspective. He is also responsible for the offset bays and large curving walkways around the towers encouraging Bridge pedestrians to pa
ause and enjoy the view.
Construction of the bridge began on January 5, 1933. Foundations were dug out of the hillsides to hold the deep-set anchorages that would support the concrete pylons. Strong tides and heavy swells hampered construction of the south pier, the keystone of the entire structure, which required excavating in hard rock 65 feet below the surface of the water.
The steel sections of the Bridge’s towers were fabricated in Bethlehem, Pennsylvania and sent by rail to East Coast seaports where they shipped via the Panama Canal to the McClintic-Marshall Corporation’s storage yards in Alameda. From Alameda the steel was taken by barge across the Bay to the Golden Gate construction site. The girders were hoisted by giant cranes and erected by gangs of men working in teams to bond the sections together with rivets and hot steel.
Strauss chose John A. Roebling and Sons of New Jersey, builders of the Brooklyn Bridge, to spin the cables. Because no derrick could lift cables as heavy as these would be, the Roebling Company spun the cables on site, from anchorages in San Francisco and Marin. Steel saddles provided a seat for the cables (and workers) as they passed over the tower to
ops. The crews spinning the cables used catwalks to travel from one side of the channel to the other. These catwalks of wire rope and redwood planking were the first structures to span the Golden Gate. Six months later, when the cabling was completed, the roadway was built. The roadway is comprised of poured concrete with copper expansion joints every fifty feet.
SUSPENSION STRUCTURES

DEFINITION
Suspension structures are those with horizontal planes (road decks, roofs, and even floors) supported by cables (hangers) hung from the parabolic sag of large, high-strength steel cables.

STRUCTURAL CHARACTERISTICS
The strength of a suspended structure is derived from the parabolic form of the sagging high-strength cable. This parabolic form is designed so that its shape closely follows the exact form of the moment diagram(s). This creates a highly efficient structure. The sagging cable performs best under symmetric loading conditions because the cable may deform significantly as it attempts to adjust to an eccentric loading. As the cable adjusts to this load it shifts the rest of the structure. Th is adjustment causes secondary stresses in the horizontal surface and additional deformation. The parabolic curve of the cable is also susceptible to developing harmonics from eccentric or lateral loads such as wind. These increased harmonics can create great movement in a structure, sometimes enough to cause dramatic failure, as in the case of the Tacoma Narrows bridge. Rather extensive calculations must be made to determine the natural frequency of a suspension structure and to test the stiffness of its horizontal surface in order to prevent the structure from developing destructive harmonics.

CONSTRUCTION CHARACTERISTICS
The horizontal surface (bridge deck, etc.) is usually a simple or continuous beam, most commonly configured as a truss or box beam. The box beam is advantageous because it resists tensional forces well, although it provides a greater surface area subject to wind loading. The large curving cable consists of many, many smaller cables which are tightly spun together. As the cables are being spun together they are also stretched over the span and attached to the supports. After being attached the appropriate curve is created by tensioning the cable. This curve is formed without the real dead load of the structure, therefore the completed curve has a different shape than the one created during construction. Finally, the horizontal surface supported by the cable is hung piece by piece from the sagging cable.

TYPICAL MATERIALS
The horizontal surface is most commonly a steel structure because of its relative lightness, or a steel and concrete composite. The towers may be of either stone, concrete, or steel. The cables are steel. Funding
Not everybody saw the value of building the Golden Gate Bridge. Yet, even during a time of unemployment and bread lines, support from the Bay Area counties was gained for a $35,000,000 construction bond issue. Gaining this support took nearly four times as long as the actual construction of the bridge. Over the years, corporate, private, and city monies have all played a role in maintaining the bridge.
Lighting
Consulting Architect Morrow understood that uniform illumination would cast an artificial light on the elegant lines of the bridge. So, the bridge has less light at the top than the bottom, creating the illusion that the bridge soars upward and becomes one with the clouds (or fog). Though the original low pressure roadway lights were replaced with high pressure sodium vapor lamps in 1982, an original lamp can still be seen behind the Roundhous Gift Center just east of the Toll Plaza
Fog Horns
The original horns were two-toned warnings to ships, as well as residents, of fog conditions. In 1985, these unique horns sounded their last. Replacement parts were no longer available so single-toned horns, all differing in frequency from one another, were installed. Each horn has a distinctive pitch to communicate a different message. Vessel operators heading into the Bay steer left of the south pier horn and right of the mid-span horn. Outbound vessels stay to the right of the mid-span horn. The fog horns operate roughly two and a half hours a day. In March, one of San Francisco’s clearest months, you’ll hear them less, but from July through October, you can expect to hear them as much as five hours a day.
Description of Work:
A Joint Venture with The Obayashi Corporation, this project is the second phase of three to retrofit the Golden Gate Bridge. Phase II of the Golden Gate Bridge includes retrofit work on the South Approach Viaduct, South Anchorage Housing, South Pylons, and the Fort Point Arch. The Project began on June 4th of 2001 and will continue until spring of 2005. When finished the bridge will be able to withstand nearby earthquake that has a magnitude of up to 8.3.
The main emphasis of the retrofit is the steel plating of the inside and outside of the two pylons that border the Fort Point Arch, the strengthening and/or replacement of the steel in the South Approach Viaduct and the Fort Point Arch, increasing the size and depth of the Pylon foundations, adding additional shear wall support to the South Anchorage House, Increasing the thickness of the East Anchorage House Wall and completely replacing the West Anchorage House Wall.
Over the duration of the project 13,838 cy of concrete will be poured, 316,444 sf of concrete formwork will be constructed, 9,314,427 lbs of steel will be erected, 15,180 cy of native soil will be excavated, and 78,164 lf of concrete will be cored.
Because of the status of the Golden Gate Bridge and the Fort Point many additional issues have to be resolved in order for the project to remain on schedule. The limited space and non-stop bridge traffic also creates access as well as safety issues. Due to the height and extent of the bridgework there are several different levels of work areas, which create a constant safety and coordination concern. All these issues place a premium on communication between workers, engineers, superintendents, inspectors, suppliers, and subcontractors.
Golden Gate Bridge Facts – Size
The Golden Gate Bridge was the longest span in the world from its completion until the Verrazano Narrows Bridge was built in New York in 1964. Today, it still has the seventh-longest main span in the world.
• Total length: Including approaches, 1.7 miles (8,981 feet or 2,737 m).
• Middle span: 4,200 feet (1,966 m).
• Width: 90 feet (27 m).
• Clearance above the high water (average): 220 feet (67 m).
• Total weight when built: 894,500 tons (811,500,000 kg).
• Total weight today: 887,000 tons (804,700,000 kg). Weight reduced because of new decking material.
• Towers:
o 746 feet (227 m) above the water.
o 500 feet (152 m) above the roadway.
o Each leg is 33 x 54 feet (10 x 16 m).
o Towers weigh 44,000 tons each (40,200,000 kg).
o There are about 600,000 rivets in EACH tower.
Golden Gate Bridge Facts – Construction Details
Eleven workers died during construction, a new safety record for the time. In the 1930s, bridge builders expected 1 fatality per $1 million in construction costs, and builders expected 35 people to die while building the Golden Gate Bridge. One of the bridge’s safety innovations was a net suspended under the floor. This net saved the lives of 19 men during construction, and they are often called the members of the “Half Way to Hell Club.”
• Steel:
o Made in New Jersey, Maryland and Pennsylvania, and shipped through the Panama Canal.
o Total weight of steel: 83,000 tons (75,293,000 kg).
• Cables:
o Two main cables pass over the tops of the main towers and are secured in concrete anchorages 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 two main cables, and it took over six months to spin them.
o Cable diameter (including wrapping): 36 3/8 inches (0.92 m).
o Cable length: 7,260 feet (2,332 m).
• Lights:
o 128 lights are installed on the bridge roadway. They are 250-watt high pressure sodium lamps installed in 1972.
o The 24 tower sidewalk lights are 35 watt low pressure sodium lamps.
o 12 light illuminate each tower, 400 watts each, and an airway beacon tops each tower.
Golden Gate Bridge Facts – Traffic
• Average crossings: About 40 million per year, counting both north- and southbound crossings, compared to 33 million crossing the first year it was open.
• Fewest crossings: January, 1982, during a storm which closed U. S. 101 north of the bridge. On January 6, only 3,921 southbound vehicles passed the toll gates.
• Most crossings: October 17, 1989, after the Loma Prieta earthquake, when Bay Bridge was closed. 162,414 vehicles (counting those going both directions) crossed the bridge that day.
• Total crossings: Through October 30, 2002, the Golden Gate Bridge Highway District says 1,754,094,967 vehicles crossed the bridge.
• Closures: The Bridge has been closed three times for weather, for gusting winds over 70 mph. It was also closed briefly for visits by President Franklin D. Roosevelt and French President Charles DeGaulle. It was also closed on its fiftieth birthday.
Golden Gate Bridge Facts – Important Dates
• May 25, 1923: The California state legislature passes a law creating the Golden Gate Bridge and Highway District
• August 27, 1930: Joseph B. Strauss submits final plans.
• November 4, 1930: $35 million bond issue approved by the six counties in the District, by a vote of 145,667 to 46.954.
• January 5, 1933: Construction begins.
• May 27, 1937: Bridge opens to pedestrians.
• May 28, 1937: Bridge opens to automobiles. The toll was 50 cents one way, $1 round trip and 5 cents charge if there were more than 3 passengers.
• February 22, 1985: The 1,000,000,000th car crosses the bridge. Toll is $2 southbound on Friday and Saturday, $1 otherdays. No northbound toll.
• May 28, 1987: Bridge closed to vehicles for its fiftieth birthday. An estimated 300,000 pedestrians jammed the bridge.
• September 1, 2002: Toll increased to $5 southbound. No northbound toll.
Golden Gate Bridge Facts – Paint
• The Golden Gate Bridge’s paint color is orange vermillion, also called international orange. Architect Irving Morrow selected the color because it blends with the bridge’s setting
• The bridge was fully painted when it was first built and then touched up for the next 27 years. In 1965, the original paint was removed because of corrosion and replaced with a inorganic zinc silicate primer and an acrylic emulsion top coat, a project that took 30 years. Today, painters touch up the paint continuously.
• 38 painters work on the bridge, along with 17 ironworkers who replace corroding steel and rivets.
Miscellaneous Construction Facts
To build the pier to support the south tower, construction workers pumped 9.41 million gallons or 35.6 million liters of water out of the fender that was constructed first.

In spite of the stock market crash of 1929 and rising unemployment, the voters in six Northern California counties approved a bond issue in 1930 to build the bridge. The amount was $35 million. It was a vote of confidence in the future.
The counties were: Del Norte, Napa, Marin, Mendocino, San Francisco, and Sonoma. The six counties now form the Golden Gate Bridge and Highway District.
Work on the bridge began on January 5, 1933.
The south pier had to be built 1,100 feet from land in water 65 feet deep. Strong tides, gale force winds and fog caused delays. A freighter rammed the trestle just after it had been completed. Following repairs a storm carried away an 800 foot section.
The design of the bridge saved old Fort Point, but not without opposition. A faction wanted it destroyed claiming it spoiled the view of the bridge. The fort is now a popular attraction.
To provide a base for the erection of the tower more than 125 thousand cubic yards of concrete went into the south pier. The footings extended 20 feet into bedrock.
The passenger ship is the SS Yale. It offered overnight service between San Francisco and Los Angeles. After leaving the bay it was usually a rough trip down the coast.
At each end of the bridge an anchorage was built to receive the two cables. The anchorage was 150 feet long, weighed 60,000 tons and had to resist a cable pull of 62 million pounds.
The San Francisco tower is being erected by the same traveling cranes used on the now completed Marin Tower. The steel was fabricated in Pennsylvania and shipped through the Panama Canal.
Each of the two towers rises 746 feet above the water. The Marin Tower was built almost on land and had none of the problems of the offshore San Francisco tower.
The rugged Marin hills are shown being graded for the Waldo approach. Both sides of the bridge went through military property.
Spinning carriages moving at 650 feet per minute carried 27,572 wires along a length of 7,650 feet. Each cable would be compressed to a diameter of 36 inches. Wire ropes would be hung from them to hold the roadway. A section of cable is on display at the toll plaza parking lot. Working from each tower, traveling cranes laid down the steel decking that formed the roadway. The first concrete was poured January 19, 1937. Note the safety net beneath the decking. Its use saved the lives of 19 men who had fallen from the bridge. It would be involved in a tragedy a few months before the bridge opened.
The safety net that stretched the length of the bridge gave the workers a sense of protection and enabled them to move about more freely.
It could not prevent the tragedy of February 17, 1937.
Just three months before opening day, a scaffold beneath the roadway broke loose, ripping through the net, plunging it into the water. Ten men on the scaffold fell to their deaths. A plaque at the San Francisco Tower honors their memory and that of another worker who had been killed earlier.
When the San Francisco-Oakland Bay Bridge opened six months earlier thousands of people poured onto the bridge holding up auto traffic for hours.
Wisely the directors of the Golden Gate Bridge had a special day just for pedestrians and an estimated 200,000 people came.
That evening there was spectacular production, “The Span of Gold”, a musical pageant of California history.

Summary

The first part is introduction. I connected introduction and history in one part. The Golden Gate Bridge is recognized one of the 7 civil engineering wonders of the world. When it opened in 1937, the bridge had the longest main span of any suspension bridge in existence. The Golden Gate Bridge links San Francisco with California’s Marin County.
Work on the Golden Gate Bridge began in 1933. Building the bridge was difficult and dangerous. The Golden Gate Strait is swept by 60-mile-per-hour winds, fierce ocean currents and tides, and for much of the year, the bridge is shrouded in thick fog.
The second part is about design and construction. Construction of the bridge began on January 5, 1933. Foundations were dug out of the hillsides to hold the deep-set anchorages that would support the concrete pylons. Strong tides and heavy swells hampered construction of the south pier, the keystone of the entire structure, which required excavating in hard rock 65 feet below the surface of the water.
The girders were hoisted by giant cranes and erected by gangs of men working in teams to bond the sections together with rivets and hot steel.
Because no derrick could lift cables as heavy as these would be, the Roebling Company spun the cables on site, from anchorages in San Francisco and Marin. Steel saddles provided a seat for the cables (and workers) as they passed over the tower tops. The crews spinning the cables used catwalks to travel from one side of the channel to the other. These catwalks of wire rope and redwood planking were the first structures to span the Golden Gate. Six months later, when the cabling was completed, the roadway was built. The roadway is comprised of poured concrete with copper expansion joints every fifty feet.
The third part of this project is about suspensions structures. The strength of a suspended structure is derived from the parabolic form of the sagging high-strength cable. The sagging cable performs best under symmetric loading conditions because the cable may deform significantly as it attempts to adjust to an eccentric loading. The large curving cable consists of many, many smaller cables which are tightly spun together.
The horizontal surface is most commonly a steel structure because of its relative lightness, or a steel and concrete composite.
The towers may be of either stone, concrete, or steel. The cables are steel.
The fourth part of this text is about description of work. Phase II of the Golden Gate Bridge includes retrofit work on the South Approach Viaduct, South Anchorage Housing, South Pylons, and the Fort Point Arch. The Project began on June 4th of 2001 and will continue until spring of 2005.
Because of the status of the Golden Gate Bridge and the Fort Point many additional issues have to be resolved in order for the project to remain on schedule. The limited space and non-stop bridge traffic also creates access as well as safety issues.
The fifth part is about Golden Gate Bridge facts.
Total length: Including approaches, 1.7 miles (8,981 feet or 2,737 m).
Middle span: 4,200 feet (1,966 m).
Width: 90 feet (27 m).
Clearance above the high water (average): 220 feet (67 m).
Total weight when built: 894,500 tons (811,500,000 kg).
Total weight today: 887,000 tons (804,700,000 kg). Weight reduced because of new decking material.
The Golden Gate Bridge’s paint color is orange vermillion, also called international orange. 38 painters work on the bridge, along with 17 ironworkers who replace corroding steel and rivets.
And final part of this project is photos and short descriptions about miscellaneous construction.

List of literature
1. www.goldengate.com
2. www.mapwest.com
3. www.greatbuildings.com
4. www.structurae.net
5. www.the4cs.com
6. ALKONAS

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