Bridges: A Series

Bridges of Kolkata on the River Hooghly

Exploring and Observing the bridges across the Hooghly

If you live in Kolkata, you must have crossed over at least one or more of these four bridges – Howrah Bridge, Vivekanada Setu, Nivedita Setu and Vidyasagar Setu. The Howrah Bridge is the icon of Kolkata, and has appeared frequently in popular culture and the movies. People who come to Kolkata by train, generally arrive at the Howrah station, on the west of River Hooghly, and cross over the Howrah Bridge to reach Kolkata. Howrah, the twin city of Kolkata is an industrial hub, while Kolkata has been the commercial hub since the time of the British.

This article will help the layman to observe the type of structures of each of these four bridges, their characteristics and specifications, as well as the purpose they serve in connecting the twin cities by road, rail and foot for the movement of people and goods.

The technical details with a brief explanation of some of the terms used in bridge construction are given in the end notes. An explanation of these and how the bridges are constructed and work will be given in succeeding articles in this series.

We hope that whenever you cross one of these bridges, you will observe and appreciate some of the points mentioned here.

1. Howrah Bridge: The Gateway to Calcutta

View of Howrah Bridge, 1945. Source: Wikimedia Commons.
Howrah Bridge carries 4 lanes of road traffic from Strand Road including pedestrians and bicycles, and connects Howrah and Kolkata across the river Hooghly. Popularly still known as and called the Howrah Bridge, it was officially renamed as Rabindra Setu after the Nobel Laureate, Rabindranath Tagore. It is maintained by the Kolkata Port Trust.

Features of Howrah Bridge

Its design is of the suspension type balanced cantilever1 and truss arch. It is made of steel, and is 705 m (2,313.0 ft) in length, with a width of 71 ft (21.6 m) with two footpaths of 15 ft (4.6 m) on either side. And a height of 82 m. Its clearance above is 5.8 m (19.0 ft) while below it is 5.8 m (19.0 ft).

It was constructed by Braithwaite, Burn & Jessop Construction. Its construction started in 1936 and ended in 1942, and was opened on 3rd February 1943.

It carries a daily traffic of 300,000 vehicles and 450,000 pedestrians and is toll free on both ways. It is one of the busiest cantilever bridges in the world.

The old pontoon bridge that was later replaced by the Howrah Bridge
Source: http://www.astrainfotech.org/kolkatainformation/calhert/howrah_bridge.htm

To provide a solution for 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.

Construction of Howrah Bridge

The bridge does not have nuts and bolts, but was formed by riveting2 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 caissons3 of dimensions 55.31 x 24.8 m with 21 shafts, each 6.25 metre square.

The entire project cost ₹25 million. The project was a pioneer in bridge construction in India. The first vehicle to use the bridge was a solitary tram!

Specifications

Elevation of Howrah Bridge, a diagram. Source: Wikimedia Commons

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.

Vivekananda Setu

Vivekananda Setu during sunset. Source: Eclicks by Bunny, Wikimedia commons.

Vivekananda Setu, earlier known as the Willingdon Bridge and popularly still called Bally Bridge, is another bridge across river Hooghly linking the city of Howrah, at Bally, to its twin city of Kolkata, at Dakshineswar. Completed in December 1930 and opened in December 1930, it is a multispan steel bridge and was built to provide road and rail links between the Calcutta Port and its hinterland. It is 2,960 feet (900 m) long having 9 Spans in total.

The famous Dakshineswar Temple is situated on the banks of the Hooghly River near the Bally Bridge. The bridge is one of 4 bridges and the 2nd oldest bridge linking Howrah and Kolkata. Since 2007, it has a new bridge accompanying it, the Nivedita Setu, 50m downstream.

Construction

The erection and Caissoning of the Bridge was done by noted Kutchi-Mestri railway contractor and Industrialist Rai Bahadur Jagmal Raja. His nameplate can still be seen on each girder of the Bridge. Its construction started in year 1926 and was completed in year 1932. The fabrication of the bridge was done by Braithwate & Company, Calcutta.

The Bridge was built with eight spans laid at distance of 300 ft each. The length of Bridge is almost half mile with 10 km approach roads on both sides. The foundation laid with well-sinking 100 ft down the river beds, girding, erection of abutments, arching was all done by Jagmal Raja.

This Railway bridge is also important in annals of history of railway in India because for the first time the railway crossed over River Hooghly and reached Calcutta at Sealdah Terminus.

The first train that ran across the bridge was named Jagmal Raja Howrah Express by the British, acknowledging the feat of Rai Bahadur Jagmal Raja. The bridge cost over ₹1 crore (US$140,000) in those years.

Vivekananda Setu had become weak as a result of ageing, and with heavy traffic, even repairs became difficult. There was need for a second bridge. Nivedita Setu was constructed parallel to it and around 50 metres (165 ft) downstream. It was opened to traffic in 2007. Vivekananda Setu allows traffic movement upstream (Bally to Kolkata) while Nivedita Setu helps downstream transport (from Kolkata to Bally).

Nivedita Setu

Nivedita Setu from River Hoogly. Source: Jonoikobangali, Wikimedia commons

Nivedita Setu (also called Second Vivekananda Setu) is a multi-span extradosed bridge4 completed 2007 over Hooghly River connecting Howrah with Kolkata, in West Bengal. The bridge is named after Sister Nivedita, the social worker-disciple of Swami Vivekananda. Belghoria Expressway that connects the meeting point of NH 16 with NH 19 at Dankuni to NH 12, NH 112, Dumdum/Kolkata Airport and northern parts of Kolkata passes over the bridge. The bridge is designed to carry 48,000 vehicles per day.

Nivedita Setu is the first bridge in the country that is a single profile cable-stayed bridge5. By design, the height of the columns are lower than the tip of the Dakshineswar temple.

Construction

The construction of the bridge started in April 2004, by the construction giant Larsen and Toubro and was opened to traffic in a record time in July 2007.
The bridge is the India’s first multi-span, single-plane cable-supported extradosed bridge with short pylons and seven continuous spans of 110 m, totaling a length of 880 m (2,887 feet). It is 29 m wide and supports 6 lanes of traffic.

Vidyasagar Setu

Vidyasagar Setu, also known as the Second Hooghly Bridge, is a toll bridge over the Hooghly River in West Bengal, India, linking the cities of Kolkata and Howrah.

With a total length of 823 metres (2,700 ft), Vidyasagar Setu is the longest cable–stayed bridge in India. It is also an extradosed bridge. It was the second bridge to be built across the Hooghly River and is named after the educationist reformer Pandit Ishwar Chandra Vidyasagar.

It cost ₹3.88 billion to build. The project was a joint effort between the public and private sectors, under the control of the Hooghly River Bridge Commissioners (HRBC).

Vehicles seen plying on Vidyasagar Setu, with the Victoria Memorial in the skyline.
Source: Wikimedia commons, DasArtitra.

The bridge was designed by Schlaich Bergermann & Partner, and checked by Freeman Fox & Partners and Bharat Bhari Udyog Nigam Limited. Construction was carried out by the consortium of The Braithwaite Burn and Jessop Construction Company Limited (BBJ). The Hooghly River Bridge Commission (HRBC) was responsible for the commissioning operations of the bridge.

Construction began on 3 July 1979, and the bridge was commissioned on 10 October 1992 by the Hooghly River Bridge Commission.

Design

Vidyasagar Setu is a cable-stayed bridge, with 121 cables in a fan arrangement, built using steel pylons 127.62 metres (418.7 ft) high. With a total length of 823 metres (2,700 ft), Vidyasagar Setu is the longest cable–stayed bridge in India. The deck is made of composite steel-reinforced concrete with two carriageways.

The total width of the bridge is 35 metres (115 ft), with 3 lanes in each direction and a 1.2 metres (3 ft 11 in) wide footpath on each side. The deck over the main span is 457.20 metres (1,500.0 ft) long. The two side spans are supported by parallel wire cables and are 182.88 metres (600.0 ft) long. Vidyasagar Setu is a toll bridge. It has capacity to handle more than 85,000 vehicles in a day.

Endnotes:
1 Cantilever – a rigid structural element which extends horizontally and is supported at only one end. Typically extends from a flat, vertical surface such as a wall, to which it must be firmly attached. Like other structural elements, a cantilever can be formed as a beam, plate, truss or slab.

When subjected to a structural load at its far, unsupported end, the cantilever carries the load to the support where it applies a shear stress and a bending moment.

2 Rivet – a permanent mechanical fastener. Before being installed, a rivet consists of a smooth cylindrical shaft with a head on one end. The end opposite to the head is called the tail. On installation, the rivet is placed in a punched or drilled hole, and the tail is upset, or bucked (i.e., deformed), so that it expands to about 1.5 times the original shaft diameter, holding the rivet in place.

3 Caissons - In geotechnical engineering, a caisson is a watertight retaining structure used, for example, to work on the foundations of a bridge pier, for the construction of a concrete dam,[2] or for the repair of ships.

4 Cable-stayed bridge – has one or more towers (or pylons), from which cables support the bridge deck. A distinctive feature are the cables or stays, which run directly from the tower to the deck, normally forming a fan-like pattern or a series of parallel lines. This is in contrast to the modern suspension bridge, where the cables supporting the deck are suspended vertically from the main cable, anchored at both ends of the bridge and running between the towers. The cable-stayed bridge is optimal for spans longer than cantilever bridges and shorter than suspension bridges. This is the range within which cantilever bridges would rapidly grow heavier, and suspension bridge cabling would be more costly.

5 Extradosed bridge – employs a structure that combines the main elements of both a prestressed box girder bridge and a cable-stayed bridge. The name comes from the word extrados, the exterior or upper curve of an arch, and refers to how the “stay cables” on an extradosed bridge are not considered as such in the design, but are instead treated as external prestressing tendons deviating upward from the deck. In this concept, they remain part of (and define the upper limit of) the main bridge superstructure.

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