Golden gate bridge is a painted orange suspension bridge spanning over Golden Gate, allowing San Francisco bay into the pacific ocean. It connects route 101 and the California state route and also to Marin County. During the year it was completed in 1937, it was the longest suspension bridge globally and now has become one of the most recognized symbols associated with san Francisco California. Since 1937 many bridges have been build that is longer but still to this day, it is the second-longest suspension bridge in America. It has been declared as ‘the modern wonders of the world by the American society of civil engineering‘(reference 1).
Before the bridge, the only connection from San Francisco to Marin County was by ferry, which was used by ‘industries to transport water which became very profitable and important for the regional economy, becoming the largest ferry operation in the world by the late 1920s‘.(reference 2) Therefore, for this reason, the San Francisco bridge was built to make transport quicker and easier and to increase the regional economy even more. ‘Joseph Strauss was the bridge’s designer and came forward to declare a bridge of this scale could be built for 17million pounds, which was unbelievable because many people believed it would be more like 100 million. He submitted sketches to the project developer Michael O’Shaughnessy and Edward Rainey, which they promoted to the whole state.
Prices start at $12
Prices start at $11
Prices start at $12
Many people liked the idea, but there were many campaigns against it by the ferry company, and there was no funding by the government. Therefore, to get the financing they needed and help promote the bridge, the three started a special district that took them six-year through all the courts to finally get the go-ahead to build the structure on the 4 December 1929‘.They financed the bridge through many construction bonds from numerous companies, and the only way of repaying this money was to charge bridge tolls for using the bridge. roughly today, motor vehicles charge $6, with axle vehicles charge $2.50 per axle and pedestrians and cyclists free of charge. (reference 1)
Strauss was chief engineer over the project but had little understanding of suspension bridges, so they hired experts in that field. Strauss’s original plan was to build a symmetrical cantilever hybrid bridge. Still, after talks with Leon Moisseiff and Charles Ellis, the experts he hired changed it to an original suspension bridge. Irving Morrow was an architect who designed the bridge’s shape, lighting setup, and arch deco theme. Leon Moisseiff produced the basic structure designs introducing his deflection theory that a thin roadway would flex in the wind and the stress would be submitted through the cables. Ellis was a Greek scholar and mathematician, so they did most of the technical and theoretical work like calculating the computation of stresses, the preparation of stress sheets, and the development of the specifications, contracts, and proposal forms.
However, he was given no credit in his lifetime through to an argument with Strauss and getting sacked before the bridge’s construction. The bridge’s construction began on 5 December 1933, with the final cost to be 35 million dollars. Strauss remained head of the project, overseeing day-by-day activities and putting safety precautions into place. The most conspicuous precaution was the safety net suspending under the bridge’s floor from end to end, saving 19 lives; however, there were eleven fatalities. The bridge was painted a vermillion orange, so it blends in with the natural setting and is used to protect the bridge from the salt content in the air, to stop corroding the steel components. The bridge painting is still an ongoing task and is the primary maintenance job.
Due to the length of the bridge being 1.7 miles long, it was split into six main structures, San Francisco (south) approach viaduct, San Francisco (south) anchorage housing and pylons S1 and S2, Fort Point arch, Suspension bridge, Marin (north) approach viaduct and Marin (north) anchorage housing and pylons N1 and N2. The bridge lighting was a complicated and important part of the structure, which had many aspects. Irving Morrow designed the whole lighting network, producing the intensity of light at different levels for different parts of the bridge. This was to further the uniqueness of the bridge. For example, the towers to be darker, so they seem to disappear into the evening darkness. In addition, the lamps glowed amber to provide warmth for the passing motorist, plus producing no glare to blind the driver.
With the light post on a slant to form an angle to achieve the arc deco theme. The lighting was finally the last piece in the jigsaw to produce a magnificent structure. The arch deco theme was achieved by simplified the pedestrian railings to small, even posts allowing motorists to have an unobstructed view by positioning the post far apart. Wide, vertical ribbing was added on the horizontal tower bracing to accent the sun’s light on the structure and rectangular tower portals themselves when thinner the higher it approaches the top. (reference 1)
The bridge’s opening was on May 27, 1937, with many celebrative events throughout the week: Including fireworks displays, overhead aircraft’s competition and many more. The bridge became a big spectacle and brought many people far and wide to see it. On the first day, many reports believed that 200,000 pedestrians walked across the bridge with thousands of automobiles to cross in the following day. Construction statistics (reference 1) Length The total length of the Bridge, including approaches from abutment to abutment, is 1.7 miles. Length of suspension span including main span and side spans: 1.2 miles.
- Length of one side span: 1,125 ft = 343 m
- Width of Bridge: 90 ft = 27 m
- Width of roadway between curbs: 62 ft = 19 m
- Width of sidewalk: 10 ft = 3 m
- Clearance above mean higher high water: 220 ft
- Total weight of each anchorage: 54,400,000 kg
- Original combined weight of Bridge, anchorages, and approaches: = 811,500,000 kg
- Total weight of Bridge, anchorages, and approaches (1937): 894,500 tons = 811,500,000 kg
- Total weight of Bridge, anchorages, and approaches in (1986): 887,000 tons = 804,700,00 kg
- Deflection and load capacity
- Maximum transverse deflection, at center span: 27.7 ft
- Maximum downward deflection, at center span: 10.8 ft
- Maximum upward deflection, at center span: 5.8 ft =
- Live load capacity per lineal foot: 4,000 lbs. = 1,814.4 kg
- Structural properties
- Height of tower above water: 746 ft
- Height of tower above roadway: 500 ft
- Diameter of one main cable including the exterior wrapping: .92 m
- Length of one main cable: 2,332 m
The structure was mainly main out of concrete and 75,293,000 kg of steel. The only way a suspension bridge can withheld its enormous weight and be stable is through the vertical cables attached to the deck. These cables support the deck of the bridge, transferring the weight to the towers at the end. The main cables continue past the tower and are anchored past the far ends of the bridge. They are carefully balanced so that the force pulling inward on the towers is equal to the force pulling outward. As a result, the weight pulls directly down into the base of the tower. The towers can be fairly thin since they aren’t being pulled to either side. The deck can also be thin since the cables are supporting it. So, therefore, the bridge is perfectly balanced and continues to rebalance its forces when loads are applied to the bridge by transferring the weight through the cables.
The advantages of suspension bridges are longer spans can be achieved than other types, and less material is required due to the cables holding the bridge up. My opinion of the bridge is that it is a magnificent practical structure that spans an enormous length to connect San Francisco to Marin county. It has made transport easier and has been a good investment because it has paid the initial bonds off through toll charges and continuously makes money. It is now the main California route 101 and would be very impractical if the bridge wasn’t built. I remember driving over the bridge and thinking how long it would take if the ferry service were still in place.
I really approve of the arc deco design and how the towers are full of detail and sculpture with sharp defining corners. Also, I think the vermillion orange really makes the bridge stand out, which can look very impressive from many miles away. The bridge has a great history of how it got constructed and still has many projects running at the moment(e.g. putting suicide barriers into place) . The bridge is definitely a focal point and feature of San Francisco, which must be seen if visited.
- ‘Research library/construction information.Golden Gate Bridge, Highway and Transportation District. http://goldengatebridge.org/research/construction.php. 2006-2010
- Two Bay Area Bridges”. US Department of Transportation, Federal Highway Administration. http://www.fhwa.dot.gov/infrastructure/2bridges.cfm. Retrieved 2009-03-09.