Bridges are structures constructed to overcome the obstacles without closing the way on which they are built, water body, valley or road so as to provide the passage over that obstacle. Earlier they were constructed with wood, planks and even stones using a simple support. Depending on the design forces of tension, compression, bending and torsion they are of various types like Beam type, Truss type, Cantilever type, Arch type, Tied Arch type, Suspension type, Cable stayed type and many more. Some of them are described as follows:
Rajiv Gandhi Sea Link/Bandra-Worli sea link:
it is cable stayed with pre-stressed concrete and steel that hangs with ducts on either side. It connects Bandra in west Mumbai to Worli in the south. Its costs about 16 billion rupees, and was constructed by Hindustan Construction Company. It has eight lanes. The main advantage of it is that it reduces travel time between both points from 60-90 minutes to 20-30 minutes. The daily traffic that passes by on it is around 37,500 vehicles. The main reason behind its construction was the congestion on the Mahim’s Causeway that was the only connecting road between western Mumbai to the central business district. The project was commissioned by MSRDC. Its foundation was led by Bal Thackeray in 1999. Its total length is 5.6 km and is 66 feet wide.
Mahatma Gandhi Setu:
it is also known as Ganga setu. It connects Patna to Hajipur in north Bihar. It is built over river Ganga. Its length is 5,750 meters and is the longest one in India. It was constructed by Gammon India Limited. Its construction started in the year 1972 and ended in 1982. It was inaugurated by PM Indira Gandhi in. It has 4 lanes and a pedestrian pathway on each side. It is made up of concrete and steel. There are total 40 piers in water on which the setu stands. Its cost was 87.22 cr.
Annai Indira Gandhi Setu:
it is also known as Pamban Setu. It is located at a distance of 7 km from Rameshwaram. Its length is 2.3 km and is built with artificial sandstone. The whole structure stands on 43 pillars and 64 pillars that are inside the sea. It is the second largest one after bandra-worli link.
Also known as Howrah Setu. It is constructed on river Hooghly. The structure is supported on two high piers 270 feet. It has eight tracks and two footpaths. It sees a daily traffic of about 150, 000 vehicles. It is constructed by the Braithwaite Burn and Jessop Construction Company Ltd. It is maintained by the Kolkata Port Trust. Initially it was named as New Howrah since it replaced a pontoon bridge at the same place connecting Howrah and Kolkata. The cost of the project was about 25 million rupees.
Also known as Second Hooghly Setu. It connects cities of Howrah and Kolkata. Its foundation was laid by Indira Gandhi on 20th May 1972. Its total length is 2,700 ft. and is the longest that is stayed on cables in India. It was named after reformer Pandit Ishwar Chandra Vidyasagar. The cost of its construction was 3.88 billion rupees. The daily traffic that passes by it is about 39,000 vehicles. Its construction was a joint venture between the public and the private sectors that were under the control of Hooghly River Commissioners. It is cable stayed with 121 cables that are arranged like a fan and is made up of steel and concrete.
It is constructed on Narmada River at Baruch, Gujarat. It is being built by Larsen and Turbo and Dywidag System International. Its cost of construction is 379 cr. Its length is 1.4 km with a span length of 144 mtr. and deck with 20.8 mtr. It has four lanes and connects Vadodara and Surat.
It is located in Allahabad. It is a double decked bridge that is built over the river Yamuna that runs from North to South connecting Allahabad to Naini. The upper deck has two railway lines connecting Allahabad and Naini junctions while the lower deck provides road service. The total length is 3,150 ft. and has 14 spans of 200 ft. and two of 60 ft. The foundation depth is 42 ft. and the height from low water level to underside is 58.75 ft. A unique feature of it is that among all the pillars, the 13th pillar is of the shape of foot of an elephant. It was designed by engineer Rendell. The cost of its construction was 44,46,300 rupees. It was constructed during the British Period and till now it has completed its 150 years.
Kolia Bhomora Setu:
It is constructed over river Brahmaputra in Assam. It connects Sonitpur in the North with Nagaon district in the south. It has been named after Ahom General Kolia Bhomora Phukan. The length of it is 3015 mtrs. In it the number of foundations is 27, among which 25 are open wells. It is maintained by government of Assam. Its construction began in the year 1981 and was finished in the year 1987.Its main advantage is that it helps in the development of North-East India. Two more setu are constructed over the Brahmaputra River: Naranarayana setu is situated in Bongaigaon, Assam. It was engineered by Braithwaite, Burn and Jassop Construction Company. Another bridge over it is the Saraighat setu in Guwahati.
It is built over river Kynshi and is the longest cantilever ever constructed in India with a central span of 140 mtr. It is situated in Ranikor in the West Khasi Hills district of Meghalaya, 130 km from Shillong. It was constructed by Gammon India Pvt. Ltd. One of the largest civil engineering construction company in India. The total cost of construction was 10 cr. It is near the Indo-Bangladesh border and forms a vital link. It also won the ICI MC Bauchemie Award for outstanding Concrete structures.
It is across the Son River between Dehri-on-son and Son nagar in Bihar. It is named after the first prime minister of India Jawahar Lal Nehru. It was constructed in the year 1963-65. A rail track known as Nehru setu runs parallel to it. The length of Jawahar Setu is 3,061 mtrs. The material used for its construction is stone and steel.
Thus, bridges are the backbone of a country, without them the development of a country becomes altered.