By Om Rami
What they are used for
Some bridges have in the past suffered from structural failure. This may be because of poor design and severe weather conditions. When opened in 1940 the Tacoma Narrows Bridge was the 3rd longest suspension bridge in the world. It later became known as the Galloping Gertie due to the fact that not only moved from side to side but up and down in the wind. Attempts were made to stabilize the structures with cables and hydraulic buffers but they were unsuccessful. Eventually on November 7 1940, only 4 months after it was built, the bridge collapsed in a wind of 42mph. The bridge was designed to withstand winds of up to 120 mph. The Tacoma Narrows Bridge was rebuilt in 1949.
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When the construction starts, the towers are the first to be put in place. There are usually two of them, each placed roughly one-third of the way in from the ends. A four-walled shell, the size of the support, is put in place in the water, and the water is then pumped out. This allows the workers to set the supports in place and secure them. Once in place, the shell is removed.
The larger cables are strung from one support to the other, and stretched down to the beginning of the bridge on both sides. They are anchored in place to secure them. Smaller cables are attached to the larger cables and hung down. These will hold the road. The sections of the road are raised by cranes and attached to the hanging cables. The road sections have steel supports under them to add some stiffness to an otherwise flexible roadway, and help support the weight of certain vehicles.
The arrows indicate the main cable (down below.)
Only 11 worker died during the construction of the Golden Gate Bridge, which is a safety record for the time. Around 35 people were expected to die during the construction. A net was suspended under the floor which saved lives of 19 men!
The steel cables are long enough to circle the world 3 times.
The Golden Gate bridge is the most photographed bridge in the world.
Akashi-Kaikyo Bridge is 12,828 feet which is 4 times longer than Brooklyn Bridge. It took 2 million workers and 10 years to construct it.
The steel cables used are long enough to circle the world 7 times.
It was built because in 1955 a ferry carrying over 100 children collided with another ferry which sank with 168 adults and children in the busy shipping lane.
Brooklyn Bridge is one of the oldest suspension bridges in the US.
It is the first steel wire bridge.
Brooklyn Bridge was opened for use on May 24, 1883. On that day 1800 vehicles and 150,300 people crossed the bridge.
Storebaet Bridge is 6,790 metres long in length from the islands of Zealand and Sprongo.
It is the world's second largest supension bridge with a main span of 1,624 metres.
The pylons are 254 metres above sea-level which is 26 metres higher than those of the Golden-Gate Bridge.
Tsing Ma Bridge
The Tsing Ma Bridge is the world's largest suspension bridge.
It has 2 decks that carry both road and rail traffic.
The total length of wire used in the construction is 160,000.
The height of the pylons is 206 metres.