880 m long Vivekananda Setu also called Willingdon Bridge and formerly known as Bally Bridge located about 10 km from Kolkata is a major railroad bridge over the Hooghly River constructed in 1932. A type of bridge in which the deck, the horizontal structure which allows the crossing, is hung by means of cables or rigid elements vertical to a number of main cables.
The main cables are generally supported at the ends of the bridge or on the piers of the bridge towers. Since ancient times, this type of bridge has been used by mankind to cross obstacles. With the passing of the centuries, the introduction and improvement of the different building materials , this type of bridges were capable of withstanding the traffic and even railway lines. Today, this type is used only for bridges of great light.
The first to theorize, in the sixteenth century, the construction system of suspension bridges was Fausto Veranzio that, in his book Machinae novae, points declamation Latina, Gallica, Hispanica et Germanica, illustrated, with engravings, two types of suspension bridges one on the other with ropes and metal chains a cable-stayed bridge.
The current form of suspension bridges was developed at the beginning of the nineteenth century ; since then bridges of this type have been built around the world. The first experiments were carried out in the United States of America where James Finley patented a suspension bridge with iron chains and built in 1802 a bridge over the River Jacobs Creek, Pennsylvania. To this was followed by others even light rather small.
After the experiences in the United States, the first European achievements took place in Britain where the development of metallurgy could offer high-performance materials that enabled the achievement of substantial light. Between 1819 and 1820 it was built the Union Bridge 137 meters, on the River Tweed on the border between Scotland and England, designed by naval captain Samuel Brown and made with chains.
Thomas Telford, the most important figure of the period, built between 1819 and 1826, the suspension bridge over the Menai, a strait between the island of Anglesey and the mainland of Wales. The bridge was built with sixteen suspension chains, each consisting of 935 iron bars forged (now steel), on a light well of 176 meters. At the time of construction was the longest bridge in the world. Among the first to be built, there is also the first bridge to Hammersmith ( 1827 ), in London of William Tierney Clark .