_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 ofsteel , 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,thefirst stone was laid on the 7 October 1925 ,although the stone surrounds were only to m…