Howrah bridge is 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.
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INTRODUCTION TO HOWRAH BRIDGE: -
- Howrah Bridge is a cantilever bridge with a suspended span over the Hooghly River in West Bengal, India.
- 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.
- 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 6.25meter square.
- 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 were diverted for 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 were asked to supply the remaining 23,000 tons of high tension steel.
- The Tata’s developed the quality of steel required for the bridge and called it Tiscom.
- The entire 23,000 tons was supplied in time. The caisson at Kolkata side was set at 31.41 m and that at Howrah side at 26.53 m below ground level.
- The work on the foundation was completed on November 1938.
- By the end of 1940, the erection of the cantilevered arms was commenced and was completed in mid-summer of 1941.
- The two halves of the suspended span, each 282 feet (86 m) long and weighing 2,000 tons, were built in December 1941.
- The bridge was erected by commencing at the two anchor spans and advancing towards the center, with the use of creeper cranes moving along the upper chord.
- 16 hydraulic jacks, each of which had an 800-ton capacity, were pressed into service to join the two halves of the suspended span.
- The entire project cost ₹25 million (£2,463,887).
Specifications OF HOWRAH BRIDGE: -
- When commissioned in 1943, Howrah was the 3rd-longest cantilever bridge in the world, behind Pont de Québec (549 meters (1,801 ft.) in Canada and Forth Bridge (521 meters (1,709 ft.) in Scotland.
- It has since been surpassed by three bridges, making it the sixth-longest cantilever bridge in the world in 2013.
- It is a Suspension Type Balanced Cantilever bridge, with a central span 1,500 feet (460 m) between centers of main towers and a suspended span of 564 feet (172 m).
- The main towers are 280 feet (85 m) high above the monoliths and 76 feet (23 m) apart at the top.
- The anchor arms are 325 feet (99 m) each, while the cantilever arms are 468 feet (143 m) each.
- The bridge deck hangs from panel points in the lower chord of the main trusses with 39 pairs of hangers.
- The roadways beyond the towers are supported from ground, leaving the anchor arms free from deck load.
- The deck system includes cross girders suspended between the pairs of hangers by a pinned connection.
- Six rows of longitudinal stringer girders are arranged between cross girders. Floor beams are supported transversally on top of the stringers, while themselves supporting a continuous pressed steel troughing system surfaced with concrete.
- The longitudinal expansion and lateral sway movement of the deck are taken care of by expansion and articulation joints.
- There are two main expansion joints, one at each interface between the suspended span and the cantilever arms, and there are others at the towers and at the interface of the steel and concrete structures at both approach.
- There are total 8 articulation joints, 3 at each of the cantilever arms and 1 each in the suspended portion.
- These joints divide the bridge into segments with vertical pin connection between them to facilitate rotational movements of the deck.
- The bridge deck has longitudinal ruling gradient of 1 in 40 from either end, joined by a vertical curve of radius 4,000 feet (1,200 m).
- The cross gradient of deck is 1 in 48 between kerbs.
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