The Sydney Harbour Bridge Essay, Research Paper
_The Sydney Harbour Bridge_
At one stage of Australia`s history Sydney was two cities,on the south shore lived 600,000 people and on the north shore lived another 300,000 people.People would either travel to and fro by ferry or go via the Gladstone Bridge which would take several hours.The problem of linking the sides had seemed too expensive to resolve until 1922.
In 1922 the New South Wales parliament got serious and passed the Sydney Harbour Bridge Act, world bridge builders were then invited to submit designs and approximate costs ,for what would become the Sydney Harbour Bridge.These designs had to meet requirement set down by government engineers. The building of the bridge would be closely supervised by J.J.C. Bradford.
Dorman, Long and Company won the contract to build The Sydney Harbour Bridge one of the winning features was that the bridge was to be built using mainly Australian materials.Dorman, Long`s bridge was to be a two hinged steel arch bridge, with five approach spans on either side , the total lenght would be 1149meters and it would cost the government 4,217,722 pounds (250 million)
The main span of the Sydney Harbour Bridge would be two steel arches 30 meters apart
each arch is a truss,which means it is made up of steel , made in the shapes of triangles .
Triangles are very strong and cant’t be pushed out of shape like squares.
The roadway is hung of the arches ,at the end of each arch is an abutment ,which stops the arches from spreading outwards.On the top of each abutment is two towers which are there for decoration and does not hold any of the bridges weight.Five pairs of smaller trusses are at either end of the brigde and these are supported by concrete piers ,which extend the bridge over low-lying land at each end.
The excavations for the Sydney Harbour Bridge began in January 1925,the first stone was laid on the 7 October 1925 ,although the stone surrounds were only to make the bridge look more attractive. There were 40,000 stones to be quarried ,cut, and numbered , this was done at Moruya.
In September 1926 the piers for the approach span was completed and by September 1927 ,4 approach spans at the south end were finished as were 2 at the north end ,the construction of the north end was always 2-3 months behind the south end so any mistakes made were not repeated.
In September 1928 all of the approach spans were completed , and work on the stone faced abutments began.The footings were made by digging huge holes 27 meters wide ,12 meters front to back and 9 meters deep.These holes were then poured full of concrete in hexagonal shapes as this was to transfere the weight of the bridge evenly over the sandstone below.
The next step was to build the hinges that would allow the bridge to expand and shrink up to 180mm , due to weather changes. The hinges are four huge steel rods held at each side of the bridge . The steel saddles are held against the abutments and the hinges are then placed inside the saddles ,these saddles had to positioned exactly right or the bridge would not had aligned making it useless.
The unfinished arch extending over the harbour was supported by steel cables ,thread through the steel and anchored in massives tunnels 40 meters long ,that was cut from the sandstone bedrock that the city of Sydney is built on.
In October 1928 the building of the steel arch began ,the steelwork was installed using a creeper crane, which is five cranes of various sizes on one travelling base.On the 26th of November 1928, 589 tonnes of steel were installed ,setting a new world record.The Sydney Harbour bridge is held together by 6 million rivets ,rivets were used because welding was to unreiliable and screws ,nuts ,and bolts were too expensive.The rivets were Australian made and supplied by McPhersons of Melbourne.
During the building of the Sydney Harbour Bridge there were only 16 workers killed compared to 121 deaths during the building of the Snowy Mountains scheme.On the 4th of August 1930 ,the northern half of the arch was finished after catching up with and overtaking the southern side ,which was completed on the 7th August 1930 ,leaving a gap of 1 meter .Supervising engineer Laurence Ennis laid a plank over the gap to become the first person to cross the Sydney Harbour Bridge.The bridge met in the middle after the tie-back cables were released to allow the two halves to tilt slowly together.
The arch was completed on 9 September 1930. After the arch was completed it was time to hang the deck, on which the road would be constructed. The shortest hanger is 7.3 meters and the longest is 58.8 meters long ,these cables support the road by hanging off the arches.This part of construction took only 9 months.
During 1931 all manner of things were completed including the concreteing and laying of the asphalt on the deck. Power ,phone, water , gas and drainage pipes also had to be carried acrossthe harbour by the bridge. The roads at either end of the bridge also had to be modified and completed. Laying of tram and railway lines were completed along with a clean up of the building site.
On January 1932 the bridge was made availiable to the New South Wales government for testing and was officially handed over on the 15 of March 1932.
Wednesday 16 March 1932 sees 10,000 school children crossing the bridge in the pouring rain ,24 hours before anybody else was able to cross the bridge.
The bridge officially opened !9 March 1932 ,the celebrations included the finish of a 550 kilometer relay of school children from Tottenham to Sydney, meetings ,sporting events, balls , dinners ,military shows, the huge party went on for two weeks.
The opening began with a message from the king and Premier Jack Lang was to have cut the ribbon ,but before he could ex- captain F.E de Groot galloped up on his horse slicing through the ribbon declaring “it open in the name of decent and loyal citizens of New South Wales”.
De Groot belonged to a para-military group called”the guard” who were enraged that a member of royalty was not invited to open the bridge.The ribbon was hastily re-tied and Jack Lang officially opened the bridge accompanied by a 21 gun salute and a fly-by by the Australian Air Force.
In its first year the Sydney Harbour Bridge carried 11,000 vehicles across the harbour.The final cost of the bridge was 10,057,170 pound 7 shillings and 9 pence.In 1988 New South Wales finished paying back the loan lent to build the brige.
FACTS
LENGHT OF ARCH : 503 METERS
TOTAL LENGHT OF BRIDGE : 1149 METERS
HIGHEST POINT : 134 METERS ABOVE SEA LEVEL
WEIGHT OF STEEL IN THE ARCH : 37,000 TONNE
TIME TO BUILD : 7 YEARS 356 DAYS
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