What Is the Golden Gate Bridge?
The Golden Gate Bridge is a suspension bridge that connects Marin County and San Francisco in the United States. The American Society of Civil Engineers declared the bridge as one of the wonders of the modern world. The bridge is one of the best examples of Art Deco architecture.
The bridge has a 1280-meter span and is 227 meters tall. The Frommer's travel guide describes the bridge as "Possible most beautiful, certainly the most photographed, bridge in the world." This article will explore the history of the golden gate bridge and its architecture.
History of the Golden Gate Bridge
Ferry services connected Marin County to San Francisco in the early 1820s. Water transportation was the initial goal. Effective connectivity was required to support San Francisco's economy, making the construction of a bridge inevitable. But building a bridge would be extremely difficult due to the powerful currents and tides that constantly swirl.
A 1916 article about the $100 million bridge by engineering student James Wilkins appeared in the San Francisco Bulletin. He also enquired as to whether it could be constructed for less money. An ambitious engineer and poet named Joseph Strauss answered with the suggestion that a cantilever bridge might be built for $17 million.
Several inputs from design engineers suggested a suspension bridge. Finally, the suspension bridge concept was approved by the authorities. However, the Southern Pacific Railroad opposed the bridge due to competition for its ferry services. Additionally, the U.S. Department of War was worried that the bridge might impede ship movement. The U.S. Navy believes that the sabotage of the bridge collision could prevent access to its main harbors.
After solving all the shortfalls, the bridge's construction started on January 5, 1933. Joseph Strauss remained the head of the project. The bridge opened on May 27, 1937.
What Is a Suspension Bridge?
A suspension bridge is a bridge in which the deck is suspended from vertical towers at each end by cables. The cables should be in a parabolic shape. Numerous cables connecting the deck to the main cables will support the bridge from beginning to end. At the bridge's end, the main cables are anchored.
Large distances can be covered in a single span using the suspension bridge. For stretches of two kilometers or more, they are useful. The 1915 Çanakkale Bridge in turkey is the longest suspension bridge in the world.
Challenges and Solutions to the Golden Gate Bridge's Construction
Balancing the Force
In suspension bridges, balancing the weight is a crucial challenge. Designing the tower's ideal height comes first. A small tower will have a low sag and cannot support as much weight as a large tower. Therefore, it is necessary to maintain the ideal tower height.
The road deck needs to be balanced so that it can support the weight even when there is traffic. The tower will flex when additional force is applied to the deck. To preserve the tower's safety, the load must be balanced.
How Was the Force Balanced?
The main cables of a suspension bridge are under tremendous tension, which causes the tower to bow inward. The main cables are extended and secured to the ground to eliminate stress. 250 pairs of vertical cables connect the main cable to the deck. Through the main cables, these cables will transmit the compression force of the deck to the towers.
A bridge's height significantly contributes to the force's balancing. Low cable tension in a high tower design allows for simple load-bearing. So, a structure was built at the ideal height of 746 meters. To ensure that the load on the bridge is balanced, the bridge was built evenly from both directions.
The suspension cables support the deck's weight and balance the overall weight when there is traffic. However, the bridge was closed to vehicular traffic in 1987 as part of a celebration marking its 50th anniversary, allowing only pedestrians to use it. The bridge's middle span has flattened out under the immense weight caused by unchecked pedestrian traffic. But the bridge's design allows it to flex when faced with heavy loads.
The weakest portion of a bridge is always the connections. The steel suspenders with concrete in a bridge are not practical here. Concretes are brittle in nature. The connections will begin to crack after a specific period of time. Over time, the cracks will make the bridge less sturdy. Such a bridge cannot even support patchwork repairs.
How Were the Connections Secured?
A steel deck is attached to the suspenders. The road deck is set on steel. Steel-to-steel couplings are consistently reliable. Therefore, the steel frame guarantees the bridge's strength. The steel deck on which the road is laid supports the bridge and ensures its stability.
What Is Thermal Expansion?
A successful structure must overcome a significant engineering challenge called thermal expansion. The concrete and steel framework will expand or contract depending on the weather. The concrete and the steel will expand on a warm, sunny day. It will increase the tension on the bridge, which will ultimately cause it to collapse.
How Was Thermal Expansion Solved?
Engineering faces a significant issue in addressing thermal expansion. The design of the Golden Gate Bridge allows it to tolerate thermal expansion. To create a full bridge, the deck is cut into seven parts and put together. Between the joints, there are finger expansion joints that allow for expansion. While traveling across the bridge, we can see the joints. On a sunny day, the finger joints can move almost four feet.
Steel has a larger thermal expansion than concrete. But if the surface is small, this won't matter much. So, every fifty feet, a little expansion joint is built. These joints will ensure expansion space.
Strong and turbulent currents and tides are characteristic of the Pacific Ocean. Additionally, the coldness of the Pacific Ocean will lead to hyperthermia. The center of the water is 372 meters deep. Building a bridge will be difficult due to the strong winds and fog.
How Were Pacific Currents Tackled?
There are powerful currents in the Pacific. The south side tower must be constructed in the water to shorten the unsupported deck's length. To ensure the tower's stability, it must be constructed on hard strata. The bomb was initially detonated under the water by trained divers. The debris was cleared, and the fender walls were built to protect the workers from the pacific currents.
A reinforced concrete slab was constructed within them to give the fender walls solidity. Inside the fender walls, a worker shaft, a material shaft, and blasting tubes were placed. Laborers excavated the concrete slab, and the fender walls were allowed to slowly sink in the water. After that, reinforced concrete was utilized to finish building the tower. The fender walls shield the tower from the dangerous Pacific currents.
They also intended to labor without difficulty in the Pacific's windy and foggy conditions. The truss was constructed in advance, transported to the site by ships, and put together one at a time using a derrick. With rivets, their connection was secured.
The Golden Gate Bridge … offers enduring proof that human beings can alter the planet with reverence.
— Kevin Starr
James Wilkins was the one who first suggested spending $100 million to build the bridge. But in response, Joseph Strauss devised a plan to build a cantilever bridge for less than $17 million, or $423 million in today's dollars. However, the condition required a suspension bridge. Finding money during the recession proved to be a significant obstacle in the bridge's construction.
How Was the Bridge Funded?
The Golden Gate Bridge and Highway District were established by a law passed by the California Assembly in 1928. It served as a legitimate organization that built the bridge. The Great Depression of 1929 made it challenging for the government to raise money to build the bridge. As a result, the district issued $30 million worth of bonds. But until Amadeo Giannini, the founder of Bank of America, purchased the bonds in 1932, it was challenging to sell them.
The 1933 construction project was completed 1.3 million dollars under budget and ahead of time. In today's dollars, the project will cost about $530 million.
Let's Thank the People Involved in the Golden Gate Bridge
Engineers put in a lot of effort to improve the lives of others. Every new invention made by an engineer will make people's lives easier. Taking a regular ferry over the worst part of the Pacific Ocean is difficult. An engineering student's proposal and an engineer's response created the most stunning bridge that unites people.
The Golden Gate Bridge did indeed link the two counties and the people in them. Eleven men gave their lives to build the bridge. Let's take a moment to express our gratitude to the engineers and workers who put in so much effort to make our journey special.
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This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
© 2022 Jagatheesh Aruchami