Willingdon Bridge
Vivekananda Setu, previously called Willingdon Bridge and Bally Bridge, is a rail and road bridge over the Hooghly River in West Bengal, India. It links the city of Howrah, at Bally, to Kolkata, at Dakshineswar.
Between 60 and 70% of the steel was obtained from the Tata Steel Company, at whose Tatanagar Works it was manufactured, while all the spans were fabricated near Calcutta by Braithwaite and Co., Ltd. India. Erection was supervised by engineers of the East Indian Railway Company.
The well foundations and piers were constructed and the girders erected on site by Rai Bahadur Jagmal Raja Chauhan.[1]
The Consulting Engineers were Rendel, Palmer and Tritton.
Construction started in 1926 and the bridge opened on 29 December 1931. The fabrication of the bridge was done at works of Braithwaite and Co (India), Calcutta.
It was by far the most expensive of the railway bridges to be constructed in India up to that time.
At the point where this spectacular structure crosses the river is 2,520 feet wide. The viaduct consists of 22 spans of 30 feet girders built on masonry piers, whose foundations have been piled with reinforced concrete piles 40 to 50 feet long. The bridge itself consists of seven 350 feet main spans and two 80 feet land spans. The eight main piers in the river are founded on octagonal steel caissons, 70 feet by 37 feet, having two dredging holes each 19 feet in diameter. The caissons were all floated into position and founded by loading with concrete, sustaining the load on compressed air buoyancy and releasing the air on a suitable falling tide.
A detail in the erection, unusual in bridge building, was the method of putting camber into the girders. Instead of building the bottom boom with the required camber in the first instance, as is usually done, the bottom boom of the Bally bridge girders was erected level on the cross girders, and then the ends of the boom were dropped four inches. (See also below for more detail). Another extraordinary feature of the bridge which makes it virtually unique in the world is that the caissons (70 feet by 37 feet) have been sunk in a tidal river in four feet of water, with a current at times six miles an hour. It may be mentioned that at periodic intervals the Hooghly River is visited by tidal bores which are known to overturn heavy boats, tear steamers from their anchors, and even pull away floating docks from their moorings. They have been the nightmare of all bridge builders and of everyone connected with navigational work in the Hooghly River. Provision had to be made for these tidal bores.
From Modern Steelwork by the British Steelwork Association, 1933:-
The piers are founded on caissons carried to an average depth of about 115 ft below Kidderpore Dock Sill. The spans have modified Petit trusses at 38 ft centres, with cross girders carried below the lower chord and extended outwards to provided cantilevered roadways.
The steelwork in each of the massive spans weighs 2400 tons. 'It was decided in order to reduce the secindary stresses, that the ends of chord members should be machined to the angles shown in the drawings and that the camber should be given by varying the lengths of members.
'The bottom booms were accordingly laid out level and jointed up and the web members inserted. The bottom boom was then jacked to the required camber, thus putting secondary stresses in the joints and causing the web members to diverge radially at their upper ends.
'Top chord members were then inserted, force being required to draw the end rakers down to the bottom chords and secondary stresses being induced in top chord joints also.
'When the spans were erected and the camber came out, these secondary stresses largely disappeared.
'Chord members were 4 feet deep and 4 feet 6 inches wide over angles, the heaviest piece weighing 22 tons. Depsite the size and weight of the pieces, joints were made and tested to 0.004 inch and the whole of the pieces for the seven spans were interchangeable.
'It is a tribute to the accuracy with which modern steel bridgework is made, that three of the spans were sent to site and erected before the shop erected span was completed.'