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OTHER ITA SITES:
Brooklyn Bridge – Creating Grandeur
This is probably the biggest and oldest infrastructure project in bridge construction that is still in use, and it wonders us that our small hands can do such a miracle when guided by the mighty mind. The project was gigantic and so was its construction. It was a battle of engineering science with nature that took lives of many during the construction, and the first one to sacrifice was the creator himself.
Any person who has sentiments, cannot cross this bridge in continuation, the grandeur and beauty compels him to stop and glance at it for a while.
Brooklyn Bridge – Creating Grandeur
In 1860, due to population explosion in New York City and Brooklyn, it was realized that a bridge was necessary to connect these cities that are separated by East River. In 1866 New York State Legislature passed the bill for construction of a bridge over the East River and New York Bridge Company was formed.
The company appointed John Augustus Roebling as its Chief Engineer on 23rd May 1867. Roebling was born on June 12, 1806, in Germany. While in school he developed an interest in both metaphysics and in bridge building. He graduated with a degree in civil engineering from the Royal Polytechnic Institute of Berlin in 1826.
In 1831 Roebling and his brother immigrated to Pennsylvania to farm. When this venture failed, Roebling accepted the position of Pennsylvania state engineer. In this position, he surveyed and supervised the construction of canals, locks, and dams.
In 1841 Roebling invented the twisted wire-rope cable, an invention which foreshadowed the use of wire cable supports for the decks of suspension bridges. Six years later he established a factory in New Jersey for the manufacture of this cable. Because the cable could support long spans and extremely heavy loads, Roebling quickly gained a reputation as a quality bridge engineer.
The gap here to be covered was 1600 ft (almost half a km) in a single span, so that ships can cross over under the span while the clear height required was 135 feet. As a chief engineer of the company, Roebling designed the Cable Suspension Bridge to meet all these requirements. Roebling then called the board of consulting engineers after completing his design to examine his plans, three other engineers from war department also examined to see whether or not the bridge would be an obstruction to navigation.
The scheme was perfect; structurally and architecturally, and the plans of Roebling were fully endorsed by both, board of engineers and the government commission. Just two months after the approval on 9th July 1869 while fixing the location of the tower on Brooklyn side, a boat bashed the slide where Roebling was standing. In this accident Roebling’s foot got crushed and in spite of medical aid, he at 63 could not bear the severe pain and died 14 days later on 22nd July.
It was a great setback for this monumental project, realizing the fact that the Roebling’s cable wire manufacturing company was the world leader in this technology; his son was anonymously chosen as his successor. Washington A. Roebling, who had not only been the accomplished associate of his father in some of his principal works, but had aided him most efficiently in the preparation of the designs and plans of this bridge.
The construction of bridge began on 3rd January 1870 and the site preparation for Brooklyn side tower started. Two towers of height 276 feet each (4 storey higher than Qutab Minar) with twin gothic arches were to be erected at the side of the river. How will they do it with foundation as deep as 78 feet? It was eight storey high foundations with solid concrete!
Digging could not be done along the side of river, as water would percolate making the digging impossible. To resolve this caisson were built for each bank. It is box structure open from one side, the open side is put on the ground; workers then go inside from trap door on the top and work inside this caisson. As digging proceeds the caisson descends by enormous wait that is put on it. To stop the water to percolate from ground, enough air pressure is generated inside the caisson which is airtight structure.
For this project huge caissons were built for each side. Workers were working under the closed wet cabin that had double the pressure that we experience normally. Under this extreme pressure nitrogen gas that is present in atmosphere is dissolved in blood which is not actually harmful, but sudden release in pressure make this gas bubble out quickly from body creating a violent pain. Also the higher pressure drives blood into central part of the body like brain, spinal cord and bone joints.
Because no one was aware of this fact workers continued to work, the result was workers were having caisson disease, they had joint pains and some of them completely paralyzed and soon died. As Washington A Roebling visited these Caissons occasionally, he contracted the same disease in May 1872 just after completing the foundations, however he was managing the project as it was his father’s dream and he has to accomplish.
After the foundations, the towers were erected. The specifications were changed from brick and stone masonry to granite and brick to make structure sturdier. The towers were fascinating and many people were visiting to see these gigantic structures across the East River. Two workers fell from these towers while construction and died instantly.
After completing the towers four main cables had to be put in place across the span that would ultimately hold the bridge deck. The cables were made of 19 strands and each of these strands was having 258 wires of 3.2mm thick each, making cable almost 16 inches thick. Each cable extending from one anchorage to other was having 320 kms of wire. Very meticulously each wire was put from one end to another and then wrapped finally.
Cabling was dangerous task, people were working on phobias height; any error could be fatal. While taking each wire one by one from one end to other, accidentally one wire slipped and cable went into the river chopping off one of the workers head. Till this stage more than a dozen workers died. Tough site conditions were becoming the greatest challenge and further to increase the humiliation of this team of 600 workers, another setback hit the project.
Washington A Roebling’s health was getting worse, he was not able to move now, he was almost paralyzed, partly blind, deaf, and mute. He now not able to supervise the project at site took his bed along the window in Brooklyn where he could see the bridge and managed the rest from there. His wife Emily was liasoning the project now and brought messages to the work site from his bed side. Emily Roebling became the surrogate Chief Engineer for the bridge and continued the work of her husband. She learned higher math and engineering through "on-the-job" training.
The 85’ feet deck weighing 6000 was built with steel structure resting on the main four cables through 1520 suspenders and 400 diagonal stays. The bridge had two lanes on either side with elevated pedestrian way in the centre.
Finally the bridge was completed on 24th May 1883 2.00 PM. The bridge at many times seemed impossible due to natures curse, shattered all records for suspension bridges of the day. It was 500 feet longer than the largest suspension bridge and extended 6000 feet from end to end.
In spite of Roebling’s inability to supervise the work, his wife did excellent effort, she was so involved in the project, that she was the first person to ride across the span during the opening ceremony while president Chester Arthur and New York Governor Grover Cleveland followed Mrs. Roebling. This was the greatest gratitude that the citizens could give to the Roebling family.
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