History of construction of Howrah Bridge which is a Suspended Balanced Cantilever steel bridge. It has completed 75 years of service.

1. Saga of a Steel Bridge
By- Pronoy RoyChowdhury
B.E (Civil) M.E (Struct) MIE CEng(I)

2. • The question of bridging the river Hooghly
flowing past the twin cities of Howrah and
Calcutta was considered for a long time past
as early as 1860.
• This is because Calcutta was then a very
important settlement of the British in India
by the bank of the river Hooghly.
• The Calcutta port was a very bustling port,
and the Howrah station a terminal station of
the then East Indian Railways where railways
used to bring passengers and goods from all
over India.

3. In 1871 an Act was passed to enable the Lieutenant
Governor (Sir G. Campbell) to construct, at the expense of
Government, a bridge across the Hughly, to fix tolls, and to
appoint the Port Commissioners to carry out the purposes of
the Act.
In moving for leave to bring in this Bill, the Hon’ ble Sir
Ashley Eden stated that a contract had been entered into
with Sir Bradford Leslie and that it was hoped the bridge
would be completed by the beginning of 1873, at a cost not
exceeding 150,000 pounds.
The several portions of the bridge were manufactured in
England and put together in Bengal. The construction of the
Calcutta- Howrah floating-bridge over the Hughly was
completed in 1874 under the supervision of Mr. (Sir)
Bradford Leslie, K. C .I. E.

5. Erstwhile Pontoon Bridge designed by by Sir Bradford Leslie

6. Sir Bradford Leslie K.C.I.E
(1831-1926)

7. Crossing the river Hooghly was an unpleasant
predicament across the narrow pontoon bridge
constructed by Sir Bradford Leslie in 1874.
The greater difficulty in deciding a proper
technology for the proposed Howrah Bridge was
due to the fact that the Calcutta port was entirely
dependent on the navigable channel of river
Hooghly and construction of any permanent pier
like structure in the valley of the river may actually
effect navigation due to the vagaries of silting and
scouring in the stream channel and consequent
reduction of navigable depth.

8. • In the year 1874 Sir Bradford Leslie the then Chief
Engineer of East India Railway designed and built a
pontoon bridge which connected Howrah with the city of
Calcutta, then the capital of British India.
• Engineers thought it shall not be a pragmatic decision
considering the fact that river Hooghly is a tidal river,
and the structure shall be exposed to severe cyclonic
storms & tidal bores which frequents in the river
Hooghly.
• However the structure effectively survived, without
any major accident. Although the bridge was built to last
for 25 years but it quiet effectively served almost 3 times
the predicted life of the structure. However with passage
of time the bridge became inadequate.

9. •A technical committee of 1909 floated global
tenders for design and specifications.
•Some 23 firms submitted technical proposals for
the same in 1913.
•The expert committee reported exhaustibly on
the submitted proposals.
•The prize was awarded to a German design
submitted by the MaschinanFabrik Augsberg et
Nurenburg Co.

10. • The German proposal basically consist of a floating longitudinal
pontoon bridge with a 200ft (about 60.96m ) opening span of
“scherzer rolling type” bascule principle with counter weighted
bascule of 100ft (30.48m) each rising up to a perpendicular position
to effect the opening. Salient features of the German proposal are
given elsewhere .
• The project was not awarded to the German Company at the time
of prevailing war, so the expert committee finally came to the
conclusion that the design did not meet all the requirements and
decided to reject all the design submitted, a new set of specification
was put up and it was decided that more designs and tenders shall be
called.
• The new specification also suggested in favour of a floating
bridge with opening spans rather than a fixed bridge owing to much
better average gradient obtained on a floating bridge.
• Inspite of significant effort the construction of the bridge was not
fruitful due to outbreak of the First World War (1914-1919).

11. Proposal for layout of Howrah Bridge as submitted by German
Company Maschinenfabrick Ausberg Nurenberg (Figure
adopted from the article "Howrah Bridge Problem" - By F.R.
Bagley, the IEI journal Vol.-I, September, 1921, Pg.-53-71)

12. •The other significant proposal was received from Sir Bradford
Leslie and he submitted a proposal for a pair of floating bridge
at the present site, which he referred to as “twin bridge”- a very
much improved type from the existing pontoon bridge with a
very ingenious type “draw spans” which was entirely a new type
of innovation designed to withdraw and restore the opening span
within two or three minutes instead of half an hour as compared
to the then old pontoon bridge, see fig for layout of the bridge.
•It was claimed that the new proposal ensured much more
stability with increased length of pontoon and punt shape ends.
The four mooring posts’ on each side of the opening span will
keep the deck span exactly in position and it was claimed that
this arrangement shall be a major improvement on stability.

13. Twin Bridge Proposal as submitted by Sir Bradford Leslie
(Figure adopted from the article "Howrah Bridge Problem" - By F.R. Bagley, the
IEI journal Vol.-I, September, 1921, Pg.-53-71)

14. The Single span Arch bridge proposal of Howrah Bridge by Sir
Basil Mott (Figure adopted from the article "Howrah Bridge
Problem" – By F.R. Bagley, the IEI journal Vol.-I, September,
1921, Pg.-53-71)

15. Sir Basil Mott a distinguished Bridge Engineer was requested by
the then Bengal Government to advise of the type of Bridge
across Hooghly. Sir Mott visited the site in the winter of 1916 and
reported around 1918 that the best type of bridge in his opinion
shall be a single span arch Bridge.

16. •Sir Basil Mott a distinguished Bridge Engineer strongly
recommended the construction of a single span arch type bridge
which he considered to have distinct advantages over any floating
bridge or bridge with piers as presenting least possible obstruction
to river traffic and with considerably less risk of scour and also
simplifying the mechanical difficulties of opening span.
•He recommended a single span steel arch of about (1400ft) (
426.72m ) span with a roadway suspended from it at a height
giving 25ft of headway at highest water level, and an opening span
of 200ft (60.9m) clear width of the scherzer or turnnion pattern.
•Although it was also admitted that there is considerable difficulty
in ensuing safe foundations for the enormous thrust coming on
abutments in Calcutta alluvium. But Sir Mott claimed to overcome
such difficulties are related to foundation. He also claimed that the
Arch type structure also has aesthetic appearance.

17. •Historically several committees were formed to
discuss the nature of the new Howrah Bridge which
shall replace the existing pontoon bridge.
Significant among these expert technical committees
was the widely referred ‘Mukherjee Committee’.
•The committee was chaired by the well known
Bengali industrialist Sir Rajendranath Mookherjee,
the other members included, Sir Clement Hindley,
the then Chairman of Calcutta Port Commissioners
and Mr. J. Mc Glashan Chief Engineer of Kolkata
Port Commissioners in 1921. This committee
suggested for Cantilever Bridge construction.

20. (1854-1936)
Sir RajendraNath Mookerjee

21. Sir Clement Hindley, the
then Chairman of Calcutta
Port Commissioners

22. In the year 1926 the new Howrah Bridge Act was
passed. In the year 1929 the consultant firm
Messers Rendel, Palmer and Tritton of Westminster
presented a report on a bridge across river Hooghly
between Howrah and Kolkata to the Calcutta Port
Commissioners. The report (as learnt from “the
Engineer” 7 Feb, 1930) is divided into two
sections each dealing with an alternative design,
the first being concerned with a bridge of
cantilever type, while the other discussing a
floating non opening bridge and in case a
preliminary cost of estimate.

24. Side elevation and cross-section of Balanced cantilever steel truss bridge Howrah Bridge put up by
Messers Rendel Palmer Tritton (figure adopted from "The Engineer" Journal, February 7th, PP 152,
1930)

25. Global tenders were floated in 1934-35 on the basis of
decision of a majority of the sub-committee of Calcutta
Port Commission ("The Engineer" 17July, 1936)
recommendations were made to accept the tender of the
Cleveland Bridge and Engineering Company Ltd. of
Darlington, for construction of New Howrah Bridge over
river Hooghly in accordance with the official design
prepared by Messers. Rendel Palmer & Tritton of
Westminster.
The contract was awarded to Cleveland Bridge and
Engineering Company Ltd, with recommendation to use
Indian Steel if proper quality of steel may be identified.
The cantilever bridge was to span 1500ft (457.2m) across
Hooghly and the width of roadway 71ft (21.6m).

26. A simply supported beam loaded with an u.d.l exhibits a
maximum B.M. of wl2/8 at the mid span, however for a fixed
beam loaded with u.d.l. It is seen that the maximum B.M. at
mid span reduces to wl2/24 thus bending stress is much reduced,
however at supports there is a hogging B.M.
•But there are some well known practical disadvantages for fixed
beam they may be indicated only for ready reference:-
•It is practically difficult to maintain the two ends of fixed beam
at same level during execution, any subsidence of support
relative to the other support shall induce sinking moments at
the support tops.
•Temperature variation will also produce large stress.
•When the beam is subjected to variation of live loads such as
wheels passing over a bridge degree of fixity at the end supports
gets reduced due to vibration of beams.

27. The above objections may however be much obviated by adopting
the double cantilever construction. In this method at the points of
contra-flexure of the fixed beam, hinged joints are introduced.
Now the beam consists of a central simply supported girder,
supported on the ends of cantilevers. The bending moment
diagram and the elastic curve for this compound beam will remain
the same as for fixed beam.
After introduction of the hinged joints, temperature changes and
support sinking will not affect the bending moments. In
comparison to totally simply support span, in cantilever
structures positive B.M. are much reduced due to reduction of
length of central span by supporting cantilever end span. In
practice obtaining perfect fixity for end cantilever supports may
be difficult to achieve. So the end cantilever spans are often
flanked to develop what is called anchor spans. With such an
adjustment, difficulty in achieving perfect support fixity may be
considerably waived.

28. Bending moment diagram, o1& O2 are distance of points of
contraflexures from support.
Fixed Beam

29. Double Cantilever with hinge at B & C
The maximum B.M. in beam BC (simply supported span
equal to
For cantilever span portion AB maximum B.M. is given by
Compound Beam

30. Thus the Maximum B.M. in the simply supported span is
whereas for the cantilevered structure the maximum B.M. is
which is about 55% of the simply supported span, hence
about 45% reduction in bending stress is achieved in balanced
cantilevered structure; so steel consumption is economized in
the truss, M=f x Z where M = B.M, f= bending stress and
Z=section modulus. Thus when M is on lower side Z required
is less so section is economical.
Comparison between Simply supported and cantilevered
structures

31. Balanced cantilever with flanking spans AE and DF and B and C are
internal Hinges
Balanced Cantilever Beam with Anchor Span (flanking span)

32. Basic Layout of Balanced cantilever truss Bridge

33. Hinge connection through eye-bar between cantilever arm
and the suspended span of suspended balanced cantilever
bridge truss

34. •A cantilever bridge consists of a simple span being carried by two
overhang or cantilever portion and the suspended span between the
cantilever spans are connected with hinge connection.
•The main advantage of a cantilever bridge over a continuous bridge is
that it is statically determinate and hence easier to analyze and also not
subjected to changes in stress due to support movements.
•Cantilever bridge construction are generally adopted for deep gorges to
be crossed by a single spans without any intermediate pier, and the
impracticability of using false work because of the danger of washout
due to high flood in river valley.
•Although cantilever bridge is less rigid and deflects more vertically than
a single span bridge, but cantilever bridge is far more rigid than
suspension bridge. But it is to mention that, each of the technology for
bridge engineering has their own relevance in engineering construction.

35. •The most significant structural feature in a cantilever bridge truss is the
provision for connection between a suspended span to the cantilever arm.
•There are hinge connection between cantilever arm and the suspended
span, this hinge is connected between two arms by a vertical link ; The link
carries only vertical forces.
•Pin connections are provided for the vertical link connecting the cantilever
& suspended span. Such pin connections are provided to achieve zero
moment or free rotation at the connections. In order to minimize friction at
the said joints high grade machining is done to make the pin and pin hole
surface smooth. To make the link between cantilever and suspended span,
eye bars are generally used.
•The ends of the eye bars are forked and eye hole is drilled in this portion.
The eye bar is inserted in the jaws of the fork end and the pin is placed, pin
is cylindrical shaped. The pin in the joint is secured by means of a cotter pin
or screw. Structurally the pin is designed as a cylindrically shaped beam.

36. •A common way to construct a cantilever bridge truss is
to counter balance each cantilever arm with another
cantilever projecting in the opposite direction, forming a
balanced cantilever bridge truss. When the courter
balancing arm is attached to a solid foundation it is called
an anchor arm. Thus in a bridge truss built on two pier
foundation, there are four cantilever arms.
• Two of them span the obstacle (river valley) and the two
are the anchor arms which extend away from the
obstacle. The Howrah Bridge is an excellent example of
suspended balanced cantilever steel truss bridge. The
deck is carried on the lower chord of the truss hanging
from suspenders.

37. •The Howrah Bridge is a suspended balanced cantilever steel truss bridge. The bridge is
primarily constructed of built up steel sections riveted together.
• The bridge is of through type; the deck hangs between the two main piers from
suspenders (hangers 39 nos) from the lower chord.
• The anchor portion does not carry the deck and they are located at ground level. The
main span of the bridge is 1500ft (457.2m) between center of the main pier.
• The main span is composed of two cantilever span and a suspended span. The two
cantilever arms are 468ft (142.6m) long and a suspended span is 564ft (171.9m).
• The anchor arms are each 325 feet (99.06m) long. The main trusses of the bridge are
spaced 76 feet (23.16m) centers and the road is 71 feet wide (21.64m) between the
kerbs accommodating eight lanes of vehicular traffic and 2 nos, 15 feet (4.5m)
cantilever footways on either side of the bridge for the pedestrian.
• The two towers of the bridge are 270 feet (82.3m) high above road level and 76ft
(23.16m) apart at the top the giant towers were bolted down at the base with the pier.
The cantilever and the suspended span are connected with pin connection, forming a
hinge. This arrangement is made through vertical member which carriers only vertical
axial load.
• There are expansion joints between the cantilever and the suspended span to
accommodate charges of temperature due to heating & cooling of the steel truss, by sun
rays etc. the main towers are sufficiently flexible to accommodate elastic deformation
of the structure in the plane of the bridge.

38. Soil reports of the main pier of Howrah Bridge
indicated that there was existence of a bed of hard
clay 97ft (29.56m) below the surface of Calcutta
and 79ft (24m) below the surface of Howrah side
pier respectively. Such revelation of clay bed
greatly simplified the scope of construction of
foundation for main pier of a single span bridge
which was out of question until then and without
such layer of soil it would have been and almost
insuperable task; for enormous loads shall be
coming on the abutment of the proposed bridge.
Soil report

39. • In 1921, The Chief Engineer of Post commissioners conducted test
to ascertain bearing capacity of the soil, and found that the bearing
capacity of the clay bed was satisfactory for a heavy bridge structure
and settlement was almost negligible.
• Messers Rendel, Palmer & Tritton the consultant Engineers firm also
conducted test with cylinders 6ft (1.82m) in dia sunk 10 ft. (3m) in hard
clay at king Georges dock of Calcutta Post Commissioners (Netaji Subhas
Dock) The test report of Rendel, Palmer & Tritton indicated that on both
sides of the river the clay bed shall provide for a factor of safety of
exactly 2, under the worst conditions of load and wind pressure.
• It was Justified that such load combination can never come in actual
practice, as at such a high wind velocity there can be little ( if any) live
load crossing the bridge.

40. •The foundation for the two main piers were giant monoliths
each of 181’6” (55.18m) long and 81’6” (24.71m) wide and
each contain 21 nos. dredging shafts each 20’6” (6.12m)
square.
•This Arrangement provided sufficient no. of dredging shafts
to give effective control along the major and minor axis while
providing ample weight on the monolith shell during sinking
to overcome skin friction and resistance of the cutting edge.
•Monoliths are essentially open cassions of reinforced
concrete or mass concrete construction with heavy walls.
• Open cassions and monoliths are suitable for foundations in
rivers and water ways where soil predominantly consists of
soft clays, silt & sands, since these materials can be readily
excavated by grabbing from open wells and they do not offer
high resistance due to skin friction to the sinking of cassion.

41. Monolith Cassion foundation of Howrah bridge under construction

42. foundation cap of Howrah bridge under construction

43. Calcutta side pier of Howrah
bridge showing one of the main
tower of the bridge truss

44. • As per recommendation of the tender for Howrah bridge, it was
required to use steel of appropriate quality & engineering property
preferably manufactured in India. In connection to the same a special
type of steel called High tensile low alloy steel containing Copper &
Chromium known commercially as “Tiscrom” was manufactured at
TISCO Jamshedpur.
• The Chemical composition of high strength steel is so balanced as to
obtain the requirement of integration of several properties such as
strength, resistance to impact, increase of corrosion and abrasion
resistance, ease of forming satisfactory welding. The available quality of
steel especially carbon steel which was widely used for bridge truss
construction could not take high stress before failure so large sections
were required adding to unnecessary dead weight and material cost.
Materials of Construction

45. •The quantity Howrah Bridge steel
weighed about 26500 tones consisted
of High tensile steel, mild steel, cast
and forged steel.
•About 17500 tons of High tensile
steel was used for Bridge
construction.

46. Carbon (C )- 0.23% to 0.28%
Manganese (Mn)- 1.0% to 1.3%
Chromium (Cr)- 0.5% to 0.6%
Copper (Cu)- 0.3% to 0.6%
Silicon (Si)- not more than 0.2%
Sulphar (S) & Phosphorus (P) not
more than 0.05% each
The chemical composition of the steel was as
follows :-

47. Nature of stress Stress in t/sq in
Axial tension (basic) = 12.65 (174.4 N/mm2)
Axial tension (Maximum) = 17.00 (234.4 N/mm2)
Axial Compression in Pin –
ended strut of length l and
radius of gyration r
= 13.8 (1 – 0.0057 l/r)
Maximum 10.75 (148.2
N/mm2)
Bending :
Tension flange = 12.65 (174.4 N/mm2)
Un-Stiffened compression
flange of length l and width b
= 12.65 (1-0.0112 l/b)
Shear in web (avg) = 7.5 (103.4 N/mm2)
Shear in shop rivets = 9.0 (124.1 N/mm2)
Bearing in shop rivets = 18.0 (248.2 N/mm2)
The engineering properties of steel are as follows

48. In 1914 the famous American bridge Engineer J. A.
Waddell in a paper (Possibilities in bridge construction by the
use of high-alloy steel, ASCE, pp 1-38, 1914) to American
Society of civil Engineers wrote “As the future development
will necessitate the building of many very long span bridges,
it is almost a necessity that there be found an alloy steel of
great strength and of moderate cost. Such alloy is not going
to be discovered by accident, but only by a lengthy and
exhaustive series of experiments laid out systematically in
advance." Waddell visualized steel with yield stress upto 45
tones / sq inch (695 N/mm2). In Howrah Bridge structural
steel with yield stress of 23 tones / sq inch (355 N/mm2) was
successfully used.

49. A large consignment of such steel about
23500 Ton was supplied by TATA Iron & Steel
Co. for construction of Howrah Bridge super
structure.
Such a lofty achievement revolutionized the
steel industry in India. The issue was highly
recognized and was even discussed at the
Presidential address of Indian Science
Congress, Benaras, 1941.

50. •But a major problem for using low alloy high
tensile steel at the time of execution of Howrah
Bridge was that British standard B.S.S. No. 548
(1934) did not specify any working stresses.
Although B.S.S. 449 (1948) specified some working
stress but it was intended for steel buildings and
not for Steel truss bridges.
• Thus Bridge Engineers therefore had to exercise
their own individual judgment in deciding
allowable stresses for high tensile steel used in
bridge work.

51. • The fabrication & erection of steel work of the Howrah
Bridge across river Hooghly of Calcutta was carried by the
contractor agency Cleveland Bridge & Engineering
Company Ltd. of Darlington, UK as per design of consultant
firm Rendel Palmer & Tritton, Westminster London.
• All the fabrication of steel work was however carried
out by the sub-contractor Braithwaite Burn and Jessop
Construction Company Ltd. in its four nos. of separate
workshops in Calcutta. BBJ was a consortium of three
Engineering companies Burn and Co. Braithwaite and
Jessop. The company was formed in 1935.
Fabrication of Structural Member

52. Fabrication of Well kerb for cassion foundation of Howrah Bridge

53. Fabrication of Links of the Anchorage truss

54. Fabrication of the
lower section of the
bridge tower

55. Girder of the anchorage truss under fabrication

56. Superstructure of
the bridge

57. • About 3700 tons of steel work was used for the main towers of Howrah
Bridge. Each tower stands on 2 inch (50mm) thick mild steel slab to which the
holding down bolt of the structural base of the tower is fired by tap bolting for
accepting the holding down bolt. The steel slab sits on supporting monolith.
• The structural base of the tower consists of seven plate Girders. The upper
flanges of which are sat up on a rake square to slope of the tower. Between
seven nos. base girders are no. of diaphragms corresponding with the webs of
the adjacent sections. The bottom section of each tower is offset to provide a
support for bearing of the main girder. The bearings were fabricated of steel
and each weighed 27 tons. The complete base measured 23 ft. (7.0m) by 17 ft
(5m).
• Above the bottom section the tower is rectangular in cross-section having
uniform width of 11 ft 6 in (3.5m) throughout in side elevation, and tapering in
transverse dimension from 8 ft 6 inch (2.6m) at bottom to 4 ft 4 inch (1.32m) at
top. The tops of towers are finished with cap plates on which saddles are
fitted. The saddles weight 115 ton and fabricates with high tensile steel plates,
157 inch (3.9m) wide and 7/8 inch (21mm) thick. Each saddle carries four pins
two of 30 inch (750mm) dia for the upper chord and two of 18 inch diameter
for the main web member.

58. Anchor, cantilever girder & suspended span
About 12000 ton steel work was used in
anchorage and cantilever arms of the bridge. In the
suspended span approximately 2100 ton of steel
work was used. The ends of the suspended span
called for a number of fitted bolts connections,
both for temporary jacking steel work to adjust the
relative positions of the two halves during erection,
and to enable the top and bottom chord gaps to be
adjusted separately.

59. Photo showing hinge and eye bar joint between Cantilever span
and suspended span of Howrah bridge

60. Anchor span view of Howrah bridge

61. Photo showing steel grillage connection with the foundation of
anchor span of Howrah bridge

62. • The road way has a clear width of 71 (21.6m) feet between the kerb and
the total width of the deck is 108 feet 9 inch (35.15m) between the centers of
fascia girders at the outer edges of two cantilevered footways.
• Deck hangers are spaced 76ft (24.16m) a past c/c transversely. The deck
system consists of cross girders at each pair of hangers, with longitudinal
floor beans spanning between the cross girders, transversal floor joists
spanning across the longitudinal floor beans and pressed steel toughing
carrying the road concrete on top. The road way troughing is filled with
concrete and a 3-inch thick (75mm) R.C. slab is placed on top.
• The slab is topped with 2-inch thick (50mm) concrete wearing surface
and is securely anchored to the troughing by hoops 8 inches (2.4m) apart
centre to centre. The footways are carried on cantilever brackets built on
ends of cross girder and the paving consists of 3-inch thick (75mm) concrete
slab with 1 1/2 inch thick (37.1mm) I.P.S. flooring.
• The bridge deck has ruling gradient of 1 in 40 from either end joined by a
vertical curve of radius 4000ft (1200m), the cross gradient of deck is 1 in 48
between the kerbs.
Deck system

63. Photo showing the roadway of Howrah bridge hanging from the
bottom chord of the bridge truss through suspenders.

64. •The superstructure of the bridge was erected with the help of a
special type of crane called creeper crane.
•It was designed especially for the work by the agency called
Wellman Smith Owen Engineering Corporation Ltd. The crane
unit was specially designed for the purpose of erection of the
cantilever bridge.
•The crane consisted of two 60 ton slewing and derricking jib
cranes lifting load at 40ft (12.19m) radius on a main frame
structure designed to travel along the top chord, the cranes had
to creep the anchor arm lying at an angle of approximately 30º
to horizontal and pass over the apex of the tower and descend
on the main cantilever chords of the central span at angles
varying for about 22º at the tower to about 9º near the end of
the arm. Therefore to form a path along which the crane has to
move ‘fleeting tracks’ were provided and placed on bridge
chords.

65. Creeper crane used
for erection of
superstructure of
Howrah bridge
truss

66. Howrah bridge
truss erected by
using creeper
crane, showing
stages of erection

67. The bridge was officially opened to
service in 1943, in the midst of 2nd
world war, so no formal opening took
place and a solitary tram crossed the
bridge. It is currently the sixth longest
cantilever bridge in the world.

68. Sir Hubert Shirley-Smith, OBE, BSc, MICE
a distinguished British Civil Engineer who
was the Chief Engineer of Howrah bridge
project and president of the Institution of
Civil Engineers London 1967

69. Maintenance of the Bridge
•It is a routine job that every 5th or 6th year the Howrah Bridge
is painted with anti-corrosive paint material. Fresh tenders
were invited by KPT in 2014 for painting of the bridge. The
Newspaper Hindu reported that about 26000 liters of lead free
paint shall be used for painting the bridge.
•The paint job shall be monitored by the National test House
Alipore for quality of paint, the thickness etc. The bridge
requires 6 coats of paint and primer to keep the bridge super
structure corrosion free.
•At first the old paint and rest shall be removed from the
structure. This is followed by two coats of a primer of Zinc
chromate which has anti-corrosive properties. Then two coats of
aluminum paint shall be applied for further protection,
following which the final two layers of chlorinated rubber based
paint shall be applied the shade will be steel colour as before .

70. •For few years a major problem was observed, that dropping of
birds, bats etc. are threatening the life of the steel structure.
These bird droppings cause gradual rusting and corrosion of the
steel sections which reduces the life span of the Bridge.
•Wastes thrown from the nearby flower market into the Hooghly
river is leading to soil and water pollution. The base structure of
the bridge is being damaged because of this pollution. As
reported in the newspaper Times of India, May 31th 2003, KPT
has engaged contractor’s for regular cleaning of bird excreta for
the steel surface of the bridge for 365 days across the year.
•They have also drawn attention of the administration and the
police to prevent throwing of flower water in the river. The
Telegraph reports that an internal study of KPT has revealed
that due to vehicular pollution & moisture corrosion was
revealed on the Bridge structure.

71. Human spitting is another major factor for corrosion of
the Bridge steel.
•A technical inspection of the Port Trust officials in 2011 as reported
by BBC News revealed that spitting has reduced the thickness of the
steel hoods protecting the Pillars from 6 to less than 3 mm in 2007.
•The hoods are of paramount importance the hangers need them at
the base to prevent water seeping into the junction of cross girders
and hangers and damage to the hoods may jeopardize the safety of
the bridge.
•Thus the KPT arranged for fiber glass casing for the base of the steel
pillars to prevent from corroding the steel structure by spit.

72. A steel truss bridge which was commissioned and opened to traffic on 1943 has
successfully served for 73 years and it is one of the most busiest bridge with heavy
vehicular traffic.
The Howrah Bridge was designed at a time when there was no well developed code
for design and construction of bridge, and the engineers had to apply their own
judgment for designing of bridges.
The material of construction, high tensile low alloy steel which was used for
construction of the bridge was a completely new type of material to be used for the
first time in such a huge quantity for bridge construction.
The major loading on the bridge during design and commissioning was only animal
driven carts, occasional motorized vehicles and military trucks during war like
activity. But now the bridge is crossed by 1,00,000 motorized vehicles daily, heavy loaded
trucks and 1,50,000 pedestrians regularly cross the bridge.
Thus the Howrah Bridge a Suspended balanced cantilever truss bridge on monolith
foundation may be easily claimed as an excellent example of steel bridge
construction which has successfully served the purpose in its service life and
continues to do so. Thus it is a perfect example of a functional heritage structure.
Conclusion

73. Thanks for listening
and patience