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Transcript of Cantilever Bridge
bridges What was the first
cantilever bridge ever built? Another successful bridge is the Firth of Forth Bridge. Up until 1917, the Firth of Forth Bridge was the longest bridge ever built. It is located at Edinburgh, Scotland with 521 meters (1,710 feet) of a clear span between its main pillars. The construction began in 1882, took 8 years to complete, cost the lives of 63 workers and used nearly 3.5 million pounds of metal. The Forth Bridge spans a total length of 2,528.7 meters and connects Scotland's capital city, Edinburgh, with Fife. Although this bridge is successful now, it had collapsed a few years earlier when it was called the Tay Bridge. This bridge makes it's country proud by being the first steel structure in the United Kingdom. What is the most successful cantilever bridge ever built? What is it? How does it work? What is it used for? What is a cantilever bridge? A cantilever bridge is a structure formed by cantilevers that are joined in the center of a suspended span. Cantilever bridges are used for any things. They are used for crossing large spans over water, especially ones with heavy loads. The bridge can carry many things such as pedestrians, automobiles, trucks, light rail and heavy rail. As it said in the video, the blue members act on compression and push the cantilever down while the orange members act on tension and pull the cantilever up. With the bottom members in compression, and top members in tension, the cantilevers connect the roadway. The Pont de Quebec (cantilever bridge)has left its mark on the history of transportation and engineering in Canada. It is crosses St. Lawrence River to Quebec City, and Levis Quebec, Canada. It is the world's longest cantilever bridge, with 549 meters (1,800 feet) of clear span between its main pillars. This feat of civil engineering was accomplished with great difficulty, and only after decades of expectation and two unsuccessful attempts that caused the death of 89 workers. The Quebec Bridge was, at last successfully completed on September 20, 1917. Today, it is considered as a world-class masterpiece and has been called as an International Historic Civil Engineering Landmark and National Historic Site of Canada. Which cantilever bridges
did not succeed? The first modern cantilever bridge was built by engineer Heinrich Gerber and his workers in 1867. The name of the cantilever bridge is Hassfurt Bridge. He designed and constructed the Hassfurt Bridge over the Main River in Germany and it has a main span of 130 meters (425 feet). Although it wasn't very long, after a few years, other people started building cantilever bridges thanks to his creation. Now, many cantilever bridges are more than 500 m! The cantilever bridge is known to be one of the strongest bridges in history! Negative: If a cantilever bridge is built over water and it collapsed, many problems can occur. Many habitats of underwater animals can be destroyed and even some animals can die because of the fallen bridge pieces.
Negative:chemicals from the materials affect the water. Cantilever bridges require a lot more material to make than other bridges. They use tons of iron, structural steel and prestressed and reinforced concrete. Because of this... What is a cantilever? A cantilever is a beam that is supported at only one end and carries a load at the other end. For example, a diving board is anchored at one end and hangs out over the pool on the other end which carries the load (the person). It would be considered a cantilever. cantilever diving board supporting end end that carries the load What are the parts of a cantilever bridge? anchor arms
the load simple truss
members in tension
members in compression load anchor arms simple truss beams members in compression members in tension Pont de Quebec Firth of Forth http://www.teachersdomain.org/asset/phy03_vid_bbcantilever/ Here is a video to show how it works: Here is another example: red= tension
green= compression BY: KOMILA Although both the Pont de Quebec and the Firth of Forth cantilever bridges are successful now, they did have difficulties during construction. The Pont de Quebec had collapsed twice while being under construction. Also, The Firth of Forth experienced a horrible disaster that caused it to fall apart.
The first time, the weight of the bridge was way over its carrying capacity and it collapsed beacause the dead load was too heavy. - August 29, 1907
The second time, when the central span was being raised into position, it fell into the river making it the world's worst bridge construction disaster. - September 11, 1916
In earlier times, the Firth of Forth bridge was called the Tay Bridge. The Tay Bridge disaster occurred during a violent storm when it collapesed while a train was passing over it. - December 28, 1879 Pont de Quebec
failures Forth of
Forth failure Cantilever bridges are very heavy. Since they depend on many strong materials, the weight of them is very massive. Ex. the Firth of Forth bridge used 3.5 million pounds of metal! The materials needed to build a cantilever bridge would cost a lot of money. Building a cantilever bridge can cost up to 100 million dollars and that is just the minimum amount. Building this structure is very expensive. Cantilever bridges are designed and constructed to be very strong and durable. Many heavy cars, trucks and trains can cross over the bridge all at once and the bridge would keep it strength. Also, they now have a proven life span extending to well over 100 years. Cantilever bridges are beneficial when crossing large spans.
The structure is very long and therefore it is useful and favourable to many people. Due to its size, this bridge is not the most economical option available. Negative: Building a cantilever bridge causes pollution in the air. The machines use too many fuels that cause pollution and if countless amounts of machines are used to construct the structure, it can cause noise pollution. The loud noises will disturb the balance of animal wildlife and people. Since cantilever bridges are one of the strongest bridges in the world, they are trustworthy to cross over. Unfortunately, there are no positive impacts of cantilever bridges in our environment. Negative:Grass land/farm land is destroyed as the structure is built on top of it