Howrah Bridge

Howrah Bridge is a bridge with a suspended span over the Hooghly River in West Bengal, India. Commissioned in 1943, the bridge was originally named the New Howrah Bridge because it replaced a pontoon bridge at the same location linking the two cities of Howrah and Kolkata (Calcutta). On 14 June 1965, it was renamed Rabindra Setu after the great Bengali poet Rabindranath Tagore, who was the first Indian and Asian Nobel laureate. It is still popularly known as the Howrah Bridge.

The bridge is one of four on the Hooghly River and is a famous symbol of Kolkata and West Bengal. The other bridges are the Vidyasagar Setu(popularly called the Second Hooghly Bridge), the Vivekananda Setu, and the newly built Nivedita Setu. It weathers the storms of the Bay of Bengal region, carrying a daily traffic of approximately 100,000 vehicles and possibly more than 150,000 pedestrians, easily making it the busiest cantilever bridge in the world. The third-longest cantilever bridge at the time of its construction, the Howrah Bridge is currently the sixth-longest bridge of its type in the world.

History of Howrah Bridge......

1862 proposal by Turnbull

In 1862, the Government of Bengal asked George Turnbull, chief engineer of the East Indian Railway Company to study the feasibility of bridging the Hooghly River. He had recently established the company's rail terminus in Howrah. He reported on 19 March, with large-scale drawings and estimates, that:

1. The foundations for a bridge at Calcutta would be at a considerable depth and cost because of the depth of the mud there.
2. The impediment to shipping would be considerable.

1. A good place for the bridge was at Pulta Ghat "about a dozen miles north of Calcutta" where a "bed of stiff clay existed at no great depth under the river bed".
2. A suspended-girder bridge of five spans of 401 feet (122 m) and two spans of 200 feet (61 m) would be ideal.

The bridge was built.

Pontoon bridge

In view of the increasing traffic across the Hooghly river, a committee was appointed in 1855-56 to review alternatives for constructing a bridge across it. The plan was shelved in 1859-60, to be revived in 1868, when it was decided that a bridge should be constructed and a newly appointed trust vested to manage it. The Calcutta Port Trust was founded in 1870, and the Legislative department of the then Government of Bengal passed the Howrah Bridge Act in the year 1871 under the Bengal Act IX of 1871, empowering the lieutenant-governor to have the bridge constructed with Government capital under the aegis of the Port Commissioners.

Eventually, a contract was signed with Sir Bradford Leslie to construct a pontoon bridge. Different parts were constructed in England and shipped to Calcutta, where they were assembled. The assembling period was fraught with problems. The bridge was considerably damaged by the great cyclone on 20 March 1874. A steamer named Egeria broke from her moorings and collided head-on with the bridge, sinking three pontoons and damaging nearly 200 feet of the bridge. The bridge was completed in 1874, at a total cost of ₹2.2 million, and opened to traffic on 17 October of that year. The bridge was then 1528 ft. long and 62 ft. wide, with 7-foot wide pavements on either side. Initially, the bridge was periodically unfastened to allow steamers and other marine vehicles to pass through. Before 1906, the bridge used to be undone for the passage of vessels during daytime only. Since June of that year, it started opening at night for all vessels except ocean steamers, which were required to pass through during the daytime. From 19 August 1879, the bridge was illuminated by electric lamp-posts, powered by the dynamo at the Mullick Ghat Pumping Station. As the bridge could not handle the rapidly increasing load, the Port Commissioners started planning in 1905 for a new improved bridge.

Plans for a new bridge

In 1906 the Port Commission appointed a committee headed by R.S. Highet, chief engineer, East Indian Railway, and W.B. MacCabe, chief engineer, Calcutta Corporation. They submitted a report stating that

Bullock carts formed the eight - thirteenths of the vehicular traffic (as observed on 27 August 1906, the heaviest day's traffic observed in the port of Commissioners 16 days' Census of the vehicular traffic across the existing bridge). The roadway on the existing bridge is 48 feet wide except at the shore spans where it is only 43 feet in roadways, each 21 feet 6 inches wide. The roadway on the new bridge would be wide enough to take at least two lines of vehicular traffic and one line of trams in each direction and two roadways each 30 feet wide, giving a total width of 60 feet of road way which are quite sufficient for this purpose [...]
The traffic across the existing floating bridge Calcutta & Howrah is very heavy and it is obvious if the new bridge is to be on the same site as the existing bridge, then unless a temporary bridge is provided, there will be serious interruptions to the traffic while existing bridge is being moved to one side to allow the new bridge to be erected on the same site as the present bridge.

Construction

The bridge does not have nuts and bolts but was formed by riveting the whole structure. It consumed 26,500 tons of steel, out of which 23,000 tons of high-tensile alloy steel, known as Tiscrom, were supplied by Tata Steel. The main tower was constructed with single monolith caissons of dimensions 55.31 x 24.8 m with 21 shafts, each 6.25-meter square. The Chief Engineer of the Port Trust, Mr. J. McGlashan, wanted to replace the pontoon bridge, with a permanent structure, as the present bridge interfered with North/South river traffic. Work could not be started as World War I (1914–1918) broke out. Then in 1926, a commission under the chairmanship of Sir R. N. Mukherjee recommended a suspension bridge of a particular type to be built across the River Hoogly. The bridge was designed by one Mr. Walton of M/s Rendel, Palmer & Triton. The order for construction and erection was placed on M/s.Cleveland Bridge & Engineering Company in 1939. Again World War II (1939–1945 ) intervened. All the steel that was to come from England was diverted for the war effort in Europe. Out of 26,000 tons of steel, that was required for the bridge, only 3000 tons were supplied from England. In spite of the Japanese threat, the then (British) government of India pressed on with the construction. Tata Steel was asked to supply the remaining 23,000 tons of high tension steel. The Tatas developed the quality of steel required for the bridge and called it Tiscom. The entire 23,000 tons were supplied in time. The fabrication and erection work was awarded to a local engineering firm of Howrah: the Braithwaite, Burn & Jessop Construction Co. The two anchorage caissons were each 16.4 m by 8.2 m, with two wells 4.9 m square. The caissons were so designed that the working chambers within the shafts could be temporarily enclosed by steel diaphragms to allow work under compressed air if required. The caisson at Kolkata side was set at 31.41 m and that at Howrah side at 26.53 m below ground level.