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IMG_7490WA - The Howrah Bridge - Calcutta, India
The Howrah Bridge is a cantilever 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 Howrah and Kolkata (Calcutta) . On 14th june 1965 it was renamed Rabindra Setu, after the great Bengali poet Rabindranath Tagore who was the first Indian and Asian Nobel laureate. However it is still popularly known as the Howrah Bridge.
The bridge is one of the 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. Apart from bearing the stormy weather of the Bay of Bengal region, it successfully bears the weight of 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, it is currently the sixth longest bridge of its type in the world.
Construction
The bridge is spectacular in the sense that it doesn't have nuts and bolts., but 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 founded with single monolith caissons of dimensions 55.31 x 24.8 m with 21 shafts, each 6.25 metre square. The fabrication was done by Braithwaite, Burn & Jessop Construction Company at four different shops in Kolkata. 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 founded at 31.41 m and that at Howrah side at 26.53 m below ground level. One night, during the process of grabbing out the muck to enable the caisson to move, the ground below it yielded, and the entire mass plunged two feet, shaking the ground. The impact of this was so intense that the seismograph at Kidderpore registered it as an earthquake and a Hindu temple on the shore was destroyed, although it was subsequently rebuilt. It is said that while clearing the muck, all kinds of objects were brought up, including anchors, grappling irons, cannons, cannon balls, brass vessels, variety of coins dating back to the East India Company. The job of sinking the caissons was carried out round-the-clock at a rate of a foot or more per day. The caissons were sunk through soft river deposits to a stiff yellow clay 26.5 m below ground level. The accuracy of sinking the huge caissons was exceptionally precise, within 50–75 mm of the true position. After penetrating 2.1 m into clay, all shafts were plugged with concrete after individual dewatering with some 5 m of backfilling in adjacent shafts. The main piers on the Howrah side were sunk by open wheel dredging, while those on the Kolkata side required compressed air to counter running sand. The air pressure maintained was about 40 lbs per square inch (2.8 bar), which required about 500 workers to be employed. Whenever excessively soft soil was encountered, the shafts symmetrical to the caisson axes were left unexcavated to allow strict control, while in very stiff clays a large number of the internal wells were completely undercut, allowing the whole weight of the caisson to be carried by the outside skin friction and the bearing under the external wall. Skin friction on the outside of the monolith walls was estimated at 29 kN/m2. while loads on the cutting edge in clay overlying the founding stratum reached 100 tonnes/m. 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 INR25 million (£2,463,887). In spite of being a pioneer in the field of bridge construction, particularly in India, there was no pomp or formal opening of the bridge due to the possibility of attacks by Japanese planes fighting the Allied Powers. The first vehicle to use the bridge was a solitary tram.
Source : en.wikipedia.org/wiki/Howrah_Bridge
IMG_7490WA - The Howrah Bridge - Calcutta, India
The Howrah Bridge is a cantilever 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 Howrah and Kolkata (Calcutta) . On 14th june 1965 it was renamed Rabindra Setu, after the great Bengali poet Rabindranath Tagore who was the first Indian and Asian Nobel laureate. However it is still popularly known as the Howrah Bridge.
The bridge is one of the 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. Apart from bearing the stormy weather of the Bay of Bengal region, it successfully bears the weight of 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, it is currently the sixth longest bridge of its type in the world.
Construction
The bridge is spectacular in the sense that it doesn't have nuts and bolts., but 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 founded with single monolith caissons of dimensions 55.31 x 24.8 m with 21 shafts, each 6.25 metre square. The fabrication was done by Braithwaite, Burn & Jessop Construction Company at four different shops in Kolkata. 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 founded at 31.41 m and that at Howrah side at 26.53 m below ground level. One night, during the process of grabbing out the muck to enable the caisson to move, the ground below it yielded, and the entire mass plunged two feet, shaking the ground. The impact of this was so intense that the seismograph at Kidderpore registered it as an earthquake and a Hindu temple on the shore was destroyed, although it was subsequently rebuilt. It is said that while clearing the muck, all kinds of objects were brought up, including anchors, grappling irons, cannons, cannon balls, brass vessels, variety of coins dating back to the East India Company. The job of sinking the caissons was carried out round-the-clock at a rate of a foot or more per day. The caissons were sunk through soft river deposits to a stiff yellow clay 26.5 m below ground level. The accuracy of sinking the huge caissons was exceptionally precise, within 50–75 mm of the true position. After penetrating 2.1 m into clay, all shafts were plugged with concrete after individual dewatering with some 5 m of backfilling in adjacent shafts. The main piers on the Howrah side were sunk by open wheel dredging, while those on the Kolkata side required compressed air to counter running sand. The air pressure maintained was about 40 lbs per square inch (2.8 bar), which required about 500 workers to be employed. Whenever excessively soft soil was encountered, the shafts symmetrical to the caisson axes were left unexcavated to allow strict control, while in very stiff clays a large number of the internal wells were completely undercut, allowing the whole weight of the caisson to be carried by the outside skin friction and the bearing under the external wall. Skin friction on the outside of the monolith walls was estimated at 29 kN/m2. while loads on the cutting edge in clay overlying the founding stratum reached 100 tonnes/m. 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 INR25 million (£2,463,887). In spite of being a pioneer in the field of bridge construction, particularly in India, there was no pomp or formal opening of the bridge due to the possibility of attacks by Japanese planes fighting the Allied Powers. The first vehicle to use the bridge was a solitary tram.
Source : en.wikipedia.org/wiki/Howrah_Bridge