Design and Construction of Pre-Tensioned Sutlej Bridge in Punjab

Paper No. 524
DESIGN AND CONSTRUCTION OF PRE-TENSIONED SUTLEJ BRIDGE IN PUNJAB †
V.N. HEGGADE*, R.K. MEHTA** & R. PRAKASH***
SYNOPSIS
Currently in vogue fast track construction has encouraged the adoption of pre-tension technology for urban flyovers. After having
successfully experimented pretensioned spans for River Bridge upto span of 30 m in Hadakiya Bridge in Gujarat, the technology was first
time extended upto 35m spans for Beas and Sutlej river bridges in Punjab. The inherent peculiarities such as single stage prestressing,
transfer of prestress through bond between concrete and cables by obviation of grouting and sheathing ducts, tensioning of tendons before
the concrete is cast and transfer of prestress after the attainment of required strength in concrete derive certain advantages in favour of
pretensioning in terms of durability, quantity reduction, construction speed, design and construction expediency. However, in the Indian
scenario there are no codal guidelines accounting for these peculiarities for bridges. The enumeration with illustration is intended to
provide basis for formulating guidelines for pretensioning in bridge building. The Paper also deliberates on optimization of beam cross
section in relation to lateral stability during transfer of prestress accounting for casting imperfections, handling and erection of beams
before the beams are transversly stiffened by deck slab which may help the code makers to have fresh look on the guidelines for lateral
stability of the prestressed beams.
1. DESCRIPTION OF THE PROJECT
The project consisted of design and construction of highlevel
bridge across the river Sutlej including approaches and
guide-bunds connecting Nakodar and Jagraon. The
construction of the bridge facilitates in reduction of the distance
between the towns by 50 km, reduction in traffic of NH-1 due to
traffic from Rajkot, Maler Kotla and Jalandar and reduction of
traffic in the city of Ludhiana. The bridge proper, 810 m long
between the inner faces of dirt walls is made up of 23 spans of
35.20 m, while the approaches of lengths 1369 m and 1115 m on
Nakodar side and Jagraon side respectively flanked the bridge
proper.
The main flow is confined and guided through the bridge
linear waterway without causing damage to the bridge and its
approaches by provision of divergent guide-bunds along the
river flow, upstream and downstream on both the banks.
The superstructure of 35.20 m span bridge consisted of 6nos.
precast pretensioned concrete beams spaced at 2.15 m
centres and cast-in-situ RCC deck slab. The width of the
carriageway has been kept 7.50 m flanked either side by 2 m
wide cycle track making the total width of the bridge deck to be
12.95 m including crash barriers and steel railings. The vehicular
way is separated from cycle ways by crash barriers while
cyclists are protected by steel railings from being toppled over.
The beams were simply supported on POT-cum-PTFE bearings
having slab steel expansion joints between the spans. The
abutments were solid non spill-through types to go with same
family of plate type piers flaring towards pier cap in the direction
* Head of Technical Mgt.
** Dy. Manager (Tech)
*** Project Manager
Gammon India Ltd., Mumbai
E-mail : vnh@gammonindia.com
† Written comments on this Paper are invited and will be received upto 30 th Sept., 2006.
of river flow (transverse) to minimise the size of the RCC cap.
The piers were founded on 6 m dia well foundations while the
abutments were resting on 7 m dia wells. The detail of the
general features of the bridge is given in Fig. 1.
2. DETAILS OF THE CONTRACT
Punjab Infrastructure Development Board, on behalf of
Punjab PWD provided developmental outline proposal with
the condition that the contractor should submit his own
proposal with the approximate dimensions of various
components of the bridge structure to fairly establish that the
technical requirement were met with. The tender proposal of
the contractors were to include certain obligatory conditions
such as length of the bridge, approaches and guide-bunds,
carriageway and cycle track width requirements, linear water
way and vertical clearance and type of foundations, and
formation levels. The departmental outline proposal had the
span of 40.50 m and the variation in span length was permitted
up to ±20 per cent. The contractor had to give detailed design
calculations and drawings in support of his proposal after the
award of the work to comply with the design requirements
stipulated in tender documents. Qualified engineers
supplemented by independent quality control consultant in
line with ISO requirements were supervising the execution of
the job.
Some of the salient design parameters specified in the tender
documents are as below:
River hydraulics

144
• Design discharge : 18912 Cumecs
• Maximum mean velocity : 4.87 m/sec
• High flood level : RL 227.868
• Depth of water at lowest : 3.0m
water level
• Scour level : RL 204.255
Seismicity
• Seismic zone : IV
• Seismic coefficient : 0075G
• Permissible increase in SBC : 25 per cent
• Permissible increase in stress : As per IRC: 6
Soil parameter
• λ (dry) : 1.8 t/m 3
• φ (angle of internal friction) : 30 0
• δ (Friction between soil and face): 20 0
• SBC for well foundation : 75 t/m 2 gross at
founding level.
Material
• For condition of exposure : Moderate
• Concrete grades
⇒For pretensioned beams : M40
⇒For well foundation : M30
⇒Reinforcements : HYSD bars
conforming to
IS:1786
HEGGADE, MEHTA & PRAKASH ON
Fig. 1. General arrangement of Sutlej bridge
Loading
• Live load :IRC 70R single lane
or Class-A 2 lanes
• Footpath live load : As per IRC: 6
• Cycle track loading : As per IRC: 6
Miscellaneous
• Type of bearings : POT and POT cum
PTFE
• Wearing coat : 25 mm thick mastic
asphalt over 40 mm
thick bituminous
concrete
• Cycle track and parapet : As per
departmental
drawing
• Software package : STAAD III -
Release 22.0
3. CONCEPTUALISATION
In many of the river bridges in Punjab upto 45 m spans, the
slab girder system with cast insitu post-tensioned beams are
successfully adopted. Beyond 45 m, upto even 65 m cast insitu
box girders are adopted. However, recently in vogue fast track

construction conceptualisation facilitates expeditious
construction. The conventional cast insitu construction and
its expediencies like staging/trestle support for superstructure
in the riverbed is not only time-consuming, also susceptible to
flood damages, consequently reducing productive working
period in a season.
In the recent years, the flyovers in urban areas especially
in metropolitan cities are realised by precast construction. The
various options in segmental and non-segmental technology
is exploited in precast construction using post-tensioning or
pre-tensioning.
In case of Sutlej Bridge, among the various options
available, finally the competition was between post-tensioned
versus pre-tensioned beams. In this particular context, pretensioned
beams had certain advantages and also peculiarities
vis-à-vis its counterpart.
The inherent peculiarities such as single-stage
prestressing, transfer of prestress through bond between
concrete and cables by obviation of grouting, sheathing ducts,
tensioning of tendons before the concrete is cast and transfer
of prestress after the attainment of required strength in concrete,
warrants specially designed casting bed which should be
capable of imparting required quantum of prestressing force.
These peculiarities derive certain advantages in favour of
pretensioned beams in terms of durability, quantity reduction,
construction speed, design and construction expediency. As
the pretensioned girders are manufactured in factory like
environment where the bonding between concrete and tendons
is direct due to the absence of grouting inside the sheathing
duct, the better durability and corrosion resistance is achieved.
The absence of the cables in the web and the elimination of end
blocks and blisters to house the anchorages, allows the section
optimisation from strength criteria alone. This helps in reducing
concrete quantities rendering in lighter beams, facilitating in
attenuation in cost of handling, transportation and erection.
The value engineering carried out during
conceptualisation stage for Sutlej Bridge revealed that for the
same span of 35.40 m and number of beams of six on the cross
section (Fig. 2), the quantities for pre-tensioned girders are
substantially lesser than post-tensioned beams.
Fig. 2. Pre-tensioning vis-a-vis post-tensioning VE for Sutlej
bridge
DESIGN AND CONSTRUCTION OF PRE-TENSIONED SUTLEJ BRIDGE IN PUNJAB
145
From the design angle, pre-tensioning uses the prestress
efficiently on smaller sections with higher eccentricities,
reduces the immediate losses like friction, wobble and slip,
reduces initial mass on substructure and foundation due to
seismic and reduces steel congestion in end blocks and
anchorage zones. Construction-wise, the activities associated
with post-tensioning such as threading of cable inside the
sheathing, grouting operation and number of prestressing
operations is eliminated.
Though the pretensioned technology has been used
extensively for flyovers and ROBs for the span range of 18 to
22 m, for the first time for bridge across river Surajbari in Gujarat
the technology was adopted with 26 m spans in India, which
withstood the otherwise catastrophic earthquake in Gujarath
on 26 th January 2001. Perhaps, it was but natural for Sutlej and
Beas Bridges in Punjab to extend the span length up to 35 m as
a part of evolutionary process, on the basis of experience gained
through the fast track flyovers and Surajbari Bridge.
4. FOUNDATIONS
Before the award of the job, as a part of tender documents
a thorough soil investigation was carried out by the department
to arrive at soil characteristics, soil bearing capacity and
founding levels along the bridge alignment (Fig. 3). Overall
seven numbers of boreholes were drilled for depths up to 40 m
and standard penetration tests were performed as per IS:2131
to arrive at ‘N’ values. Silt factors were calculated on the basis
of particle size distribution following the principles of Lacey’s
silt factor. On the basis of soil investigation, the subsoil strata
were divided into 3 distinct zones.
Around 12 m below the ground level along the alignment a
silty clay strata of average band depth of around 12 m,
designated as Zone-2 was sandwiched between sandy strata
designated as Zone-1 and Zone-3. Average value of sandy
strata was around 34 0 while clayey strata had undrained shear
strength of around 1.50 kg/cm 2 (Cu). On the basis of 75 mm
maximum settlement criteria, the bearing pressure at founding
level in sandy strata after passing through the clayey strata
was specified as 75T/m 2 on conservative side. The silt factor
for Zone-1 varied from 0.62 to 1.07 while for Zone-3 the same
was ranging between 0.35 to 1.01. The design scour depths
near the piers and abutments were evaluated on the basis of
maximum discharge, river regime and velocity of the river.
In all 22 numbers of piers were supported on 32 m deep
and 6 m dia well foundations (Fig. 4), consisting of 2.1 m deep
kerb, 1.5 m deep well cap. The steining thickness of 1.05 m is
tapered to 0.75 m at scour depth of around 18 m, below the top
of the well cap.
The thickness of the steining was decided by using the
relationship given in IRC:78 to facilitate smooth sinking by
gravity without excessive Kent ledge and damage to steining

146
HEGGADE, MEHTA & PRAKASH ON
Fig. 3. Bore hole details along bridge alignment
Fig. 4. Typical well foundation for Sutlej

due to differential earth pressure, sand blow and sudden drop,
etc. it was ensured that the stresses at different levels of steining
during service conditions and construction stage were within
permissible limits. As the well foundations were to be plugged
on soil, the grip for side earth resistance below the scour level
was ensured to be of the maximum depth of scour below the
design scour. As normally, well cannot be sunk to the precise
verticality, the design catered for the cumulative moment effect
of 1 in 80 tilts and 150 mm shift apart from accounting for other
severe load combination. The side earth resistance was
calculated by Bombay Committee Method with the passive
resistance factor of safeties of 2.0 and 1.6 for normal and seismic
conditions respectively. The well cap was designed and detailed
as uniformly thick plate for the external reactions and reaction
components at the bottom of the pier with boundary condition
as partially fixed at supports on well steining all around.
The river bed level varied between RL 222 m to 225.50 m
having deep channel between the pies P3 and P10 with the low
water level being at RL 223.723 m. Up to the deep channel i.e.
P10, the service road was made up to A/R and wells up to P10
were started simultaneously. After the monsoon was over, on
recession of floods, the service road was made on A/L side and
with the help of the site made temporary bridge between P8 and
P10; the wells were tackled in the channel.
Initially, the well sinking was planned with four cranes.
However, the sandwiched clayey strata necessitated overall
eight cranes, as the sinking through the same was consuming
almost 7 to 15 days per metre depth.
Most of the well foundations were constructed
conventionally on land, barring a couple in deep channels,
which warranted sand islands.
In the conventional construction (Photo 1.), the cutting
edge fabricated of mild steel was laid on the ground level and
curb with required reinforcements was concreted. The material
inside was gradually scooped out with grabs to facilitate sinking
under its own weight. As the sinking proceeded, the steining
was built up in lifts, normally of around 2.5 m to further the
sinking due to increase in weight.
Photo 1. Curb reinforcements & cutting edge
DESIGN AND CONSTRUCTION OF PRE-TENSIONED SUTLEJ BRIDGE IN PUNJAB
147
Since the bed profile was having large variations, almost
all wells were required to be sunk up to 5 m below the ground
level (Photo 2.) and 3.0 m below the water level. The circular
cofferdam except a small flare to accommodate piers was cast
up to water level.
Photo 2. Cofferdam with flare to accomodate pier
Had the well cap level been fixed at ground level or LWL,
the job could have been completed three to four months earlier
and substantial additional expenditure as a consequence of
taking well cap below ground level could have been saved.
As the cofferdam was quite thin compared to steining, the
non-availability of required weight hampered the sinking. This
called for the creation of the sump below the founding level to
facilitate gradual sinking. At P16 location, the sump required
was 3 m to enable last 1.80 m sinking. In the process the well
jumped and sunk by 3.70 m at one go rendering the steining top
almost 8 m (Photo 3.) below bed level.
Photo 3. Construction of well cap below GL
To raise the steining to the required level, the extensive
shoring, continuous dewatering, protection with wire crated
boulders, etc. had to be resorted to apart from stabilising the 6
m deep false walls by adequate structural bracings.
To circumvent the creation of sump to sink last 1.2 m depth
at P3 location, the other measures such as air jetting, water
jetting and Kent ledge on top of false wall were attempted.
Finally after 4 months, the combined effect of 450 t Kent ledge,
5 m excavations outside the well and dewatering yielded the
well to the required depth.

148
Though the aggregate sinking of 854 m was accomplished
in a short period of 620 days, the good engineering practice of
fixing the well cap at LWL/bed level, would have reduced the
sinking duration, efforts and its financial ramification quite
considerably.
At the every alternative well location, after reaching the
founding level, the soil investigation was carried out up to 9 m
depths to deduce ‘C’ and φ values to confirm the soil bearing
capacities. Bottom plugging was carried out by shifting the
concrete from batching plants through buckets and placing
by tremie pipes. After having done the recuperation test for
soundness of plug after 14 days, the sand filling and
intermediate plugs were expedited. With the help of
irrecoverable shuttering supported on precast beams and
cofferdam, each well cap was completed within five to six days
including reinforcement fixing and concreting.
5. PIERS
The RCC piers were of wall type flaring from well cap to
accommodate the pier cap, with the concrete characteristic
strength of 35 N/mm 2 . Though the grade of the concrete is
same as that of used for well cap, the mix had to be made little
richer with higher workability in order to enable smooth
placement of concrete for the thin sections. A system of
formwork consisting of steel channels and shuttering was used
in piers, which was concreted in two stages (Photo 4).
Photo 4. Shuttering Arrangement for Pier
The height of the first lift was 3.25 m and after concreting
the first lift, the balance second lift shuttering was fixed
immediately in 3 to 5 hours. The grout leakage through the
joints of shuttering was totally avoided by judicious planning
during the fabrication of shuttering such as overlapping of
plates, etc. The concreting for each lift was carried out in
continuous operation without the cold joint. By virtue of large
shuttering and minimum number of lifts in concreting, the surface
texture of the concrete pier has been of excellent quality.
6. SUPERSTRUCTURE
6.1 Choice of Cross Section
Due to the obvious advantages enumerated in
Conceptualisation Para, the an isotropic deck was considered
HEGGADE, MEHTA & PRAKASH ON
to be made up of 35.40 m long precast pretensioned beams,
transversely held by 200 mm thick RCC deck slab. Though the
design-wise and from aesthetical considerations, the
intermediate diaphragms could have been avoided, the same
has been provided to satisfy contractual requirement which
are in fact structurally redundant.
As there are no design criteria laid down in IRC standards
for pretensioning, invariably IRC:18 meant for post-tensioned
construction is adopted and insisted upon, for pretension
construction also. The present post-tensioned Code IRC:18
prescribes working stress method of design and permissible
stresses seem to be on highly conservative side. The
comparable AASHTO-94, the standard that is also based on
allowable stress method (ASD) design, allows at least 33 per
cent higher flexural stresses during transfer and 25 per cent
higher flexural stresses during service condition. To worsen
the matter further, the ‘IRC’ stipulates 20 per cent additional
time dependent losses, 3 times 1000 h relaxation losses, minimum
80 per cent of characteristic strength at full transfer of prestress,
those perhaps are rationalised for post-tensioned construction
on the basis of past experience, where prestress transfer is
feasible in stages.
Universally, though generally there are no separate codes
for post-tensioning and pre-tensioning, the prestressing code
itself give separate design parameters such as time dependent
loss parameters, permissible stresses and transmission length
for pre-tensioning, etc. In view of this the author had suggested
to IRC Code Making Committee to make IRC: 18 a common
code for prestressed concrete road bridges common for both
pretensioned and post tensioned concrete with the separate
design parameters wherever relevant and applicable, which is
yet to be taken into cognisance.
Selection of the beam cross section for long span
pretensioned girders warrants experience in field supervision,
apart from theoretical aspects of prestressed concrete. It is
expected that the optimum concrete section that is materially
influenced by prestressing force and loading, is light for
handling and transportation, prestressing operation and
concreting friendly. The sizes of bottom and top flanges, the
depth and width of web are required to be optimised on the
basis of above constructability issues.
The pressure line (resultant of stresses) in the prestressed
concrete flexural member shifts its location within the section
upon the application of external loads. In simply supported
beams at the midspan for service condition, the stress at the
bottom-fibre is zero, i.e. no tension allowed as per codal
provision. At the midspan pressure line is above the CG of the
section, warranting the CG of the prestressing force at a
distance equivalent to moment divided by prestressing force.
Thus to cater for the compressive force by virtue of pressure
line above the CG of section at the midspan, the top flange
requirement is high, whereas nearly zero-stressed bottom fibre

does not require flange, apart from accommodating cables.
Towards the supports as the moments are gradually reduced to
zero, the CG of the prestressing force can be judiciously located
to be concentric to avoid any requirement of flanges.
However, at the intervening stage before the application of
imposed loads including live load, the section has to store large
prestressing force at bottom fibre, which would be neutralised
on application of external intermittent loads latter, bringing the
bottom fibre stress to zero. The above calls for widening of the
bottom flange and in fact decides the width. Thus an ‘I’ section
where the pressure line can move larger distance without the
tensile stresses is chosen for pretensioned girders. While the
span to depth ratio ranges between 16 to 22, the web thickness
of 150 mm is considered to be adequate for normal ‘I’ shaped
beam for honeycomb-free concreting.
However, in case of Sutlej Bridge as the vertical clearance
was not a constraint, the lavish span to depth ratio of 14 was
adopted to reduce the prestressing strands with the web
thickness of 200 mm as constrained by IRC:18, though the same
was not required by design and constructability angles.
The decision on the width of the top flange is very crucial
as the extremely narrow top flanges may buckle the precast
beams during side shifting, transportation and handling. The
Indian Codes categorise the beams as slender beams when the
span to top flange width ratio exceeds 60 or depth to flange
width ratio exceeds 4 and specifies reduction in permissible
stresses and adequate temporary restraints during handling
and erection from lateral stability considerations. Normally,
for the simply supported beams, the span to depth ratio of 15
is considered to be optimum, and when the same is related to
depth to width ratio of 4, the span to width ratio works out to
be 60. In Sutlej and Beas bridges, 35 m long beams with 2.5 m
depth was provided with 0.70 m top flange to keep the weight
of the girder to minimum with span to flange width ratio of 50
and depth to width ratio of 3.57 satisfying both the
considerations given in Indian Codes for slenderness. The
stretching the slenderness to codal limits to keep the weight
minimum, was considered to be very bold especially after the
classical beam collapses of Roop Narayan Bridge on National
Highway No.6, where the span to width ratio 50 followed the
depth to width ratio of 3 (safer than Sutlej Bridge). In his paper
“A study of the failures during launching of precast prestressed
concrete beams of the Roop Narayan Bridge on National
Highway No. 6”, while deliberating on Guyon’s contention that
for the beams depths of 5 to 8 ft., the thickness of the flanges
should never be less than 0.1 of the depth and width of the
flanges should not be less than 0.40 of the depth for
symmetrical I-beams, Mr. Seetharaman through his
investigation concludes that the span to depth ratio should
be 15 and depth to width ratio should be less than 3 for
transverse rigidity of precast beams. Thus the chosen beam
section for Sutlej called for thorough investigation and
justification vis-à-vis lateral stability during transfer of
DESIGN AND CONSTRUCTION OF PRE-TENSIONED SUTLEJ BRIDGE IN PUNJAB
149
prestress, handling and erection of the beams before the
beams are transversely rigidised by deck slab.
The lateral stability of Sutlej beams during handling and
erection was ensured by extensive investigations on the basis
of special report “lateral stability of long prestressed concrete
beams” by Robert F. Mait in PCI Journal Jan-Feb 1989.
The improper lifting hook placement and casting
imperfection cause the beam to be tilted at an initial angle θ1 near the lifting hook location about the roll axis (Fig. 5).
Normally the casting imperfections considered 1:1920 in Sutlej
gets manifested itself by way of curvature in plan of
prestressed beam after detensioning. Lifting hook placement
tolerance was allowed to be 6.35 mm during casting. The
above tilting of beam induces the lateral deflection about
weak axis of the beam. Because of the transfer of prestress,
there is already tension at the top fibre of the beam for which
the tensile stress caused about the weak axis by the
component of the self weight due to tilt gets added which
needs to be within the permissible limits and in fact decides
the maximum tilt (θ max) to which the beam can be subjected
to. After the tilting is initiated by the initial angle θ near the
1
support locations, the beam achieves its equilibrium with a
uniform lift angle θ (shown at midspan) with CG of the mass
of the deflected beam right under the roll axis.
In the figure as Z approaches Y , the beam starts rotating
o r
and becomes totally unstable even without the initial
imperfection and without improper location of lifting hook.
Thus the safety against the lateral buckling is a measure of
Y vis-à-vis Zo and is called gross factor of safety (FOS = Y /
r r
Z ) for a perfect beam without imperfection.
o
If one has to account for imperfections causing the initial
angle q and limiting the maximum lift to θ , the factor of
1 max
safety reduces to .
However, it is more logical to deduce the factor of safety
against lateral stability by dividing maximum possible tilt θ max
with that of equilibrium rotation θ at midspan.
Moving the lifting position inwards improves the factor
of safety against lateral stability by virtue of reduced
deflections caused by rotations about the weak axis.
However, it has to be ensured that the stresses are within
the limits in overhang portions.
Though the very slender cross sections from lateral
stability considerations was chosen in Sutlej Bridge, the same
could be successfully executed by adhering to the specified
casting imperfections, lifting hook location tolerance, etc.
during execution. The details of the same are given in Fig. 5.
Unlike in post-tensioning, in case of pre-tensioning as the
strands are bonded during the transfer of prestress, the

150
Fig. 5. Laterial stability of long prestressed concrete beams with factor of safeties
beams cannot buckle which was also taken into cognisance
during lateral stability investigations.
The lateral stability guidelines for precast beams given in
Indian Codes for prestressed concrete members are similar to
that of for RCC and steel beams in terms of span to depth ratio
and depth to top flange width ratio. However, in the case of
prestressed beams, the aspect of prestressing is a new variable
and as such the same guidelines may not be applicable for
prestressed beams. In view of this the factor of safeties
enumerated above may be included for ensuring the lateral
stability of beams during shifting, transportation and erection
of prestressed, precast beams in the prestressed concrete
codes.
6.2. Design of Superstructure
The superstructure consists of six numbers of precast
pretensioned girders spaced at 2.15 m centre to centre with 250
mm thick end diaphragms to support 200 mm thick cast-in-site
RCC deck cantilevering by 1.10 m from the centre line of external
girders on either side. The pretensioned girders in the casting
yard were specified to be prestressed after 24 hours when the
strength of the concrete was 31 MPa, while the concrete grade
for the beams were M 40.
The precast girders were transported to site and placed on
bearings followed by casting of the end diaphragm. The RCC
deck slab was cast on formwork supported on girders and the
HEGGADE, MEHTA & PRAKASH ON
same was removed after the sufficient attainment of strength in
the deck. Thereafter, for the further loads such as weight of
crash barrier, wearing coat, railings and live load, etc. the
structure was assured to be a composite section. The effect of
differential shrinkage and temperature variation were also
considered in the design.
For finding all the longitudinal beam reaction components,
the grillage analysis (Fig. 6) was used for superimposed dead
loads and live loads, the structure was idealised as a grid of
longitudinal and transverse members. The composite girders
consisting of precast beam and deck slab was descretised to
be placed along the axis of the girder while deck slab and deck
slab with diaphragm was placed as transverse grillage members
along the line of each of end diaphragm in the structure. The
slab acts to transmit applied loads to beams by spanning
transversely between them, apart from providing means for
load sharing between longitudinal beams. Therefore transverse
members having slab properties were provided to reflect the
load sharing characteristics of the deck. For the application of
the loads due to railing, the dummy longitudinal members with
negligible section properties were provided at the edges and
transverse grillage members were continued to connect them.
The flaring properties of precast beams at the end for the
distance of 2.65 m from 200 mm to 300 mm thick has been
accounted for in the descretisation.
The grillage analysis results especially for superimposed

Fig. 6. Grillage idealisation for deck slab with girders
dead loads and live loads were compared with Classical Little
and Morrice method for verification, which were found to be in
agreement to a large extent as illustrated in Table 1.
TABLE 1. GRILLAGE ANALYSIS VIA-A-VIS LITTLE & MORRICE
METHOD
The stresses in bottom and top fibres of the beam before
and after the composite action were ensured to be within the
permissible limits as specified in IRC:18 at various temporary
and service stages as tabulated in Table 2.
TABLE 2. SUMMARY OF STRESSES AT MID SPAN
DESIGN AND CONSTRUCTION OF PRE-TENSIONED SUTLEJ BRIDGE IN PUNJAB
In case of the pretensioned girders with straight tendons,
151
the prestressing moments near the simply supported ends
need to be reduced as the moments induced by self weight
and external loads gradually diminishes towards the supports
from midspan. The same is achieved by preventing the portion
of the tendons from bonding, thereby preventing from
stressing the concrete at the ends. Normally, the bond
prevention is achieved by provision of tight-fitting split plastic
tube or heavy paper or cloth tape. However, for the accurate
placement of tubes after the pre-tensioning a 20 mm dia ‘PVC’
tubes were used in Sutlej Bridge as bond prevention media at
the ends (Fig. 7).
The length of bond prevention has to be deduced after
catering for “transmission length” required to develop full
tension in the tendons.
When the pretensioning tendon is stressed, the diameter
of the tendon is reduced due to poison’s effect and the original
diameter is regained after the release of prestress. In fact this
property is responsible for bonding pretensioned wires to
concrete. After the detensioning, the stress in the wire at the
end is zero and maximum after certain length, which is called
“transmission length”. The Hoyer was the first German
Engineer who developed the theory of “transmission length”
due to the formation of wedge shape in prestressing tendon
where the stress gradually decreases from maximum to zero
with the increase in diameter of tendon, which is popularly
referred as “Hoyer’s effect”.
The transmission length depends upon number of
variables, the most important being the strength of the concrete
at the time of transfer, the size of the tendon, friction between
the tendon and concrete and initial and effective stresses in
steel. As per the guidelines of IS:1343, 30 times the diameter of
the tendon for strands i.e. around 500 mm was considered as
transmission length in the said bridge. It is interesting to note
that the stress variation over transmission length being
parabolic, 80 per cent of the maximum prestress is developed
over half the transmission length, and as such half of the
transmission length was projected beyond bearing supports
for simply supported girders.
7. PRE-TENSIONING
The bridge of 23 spans consisted of 138 nos, 35.2 m long,
68 tonne weighing, prestressed beams with the depth of 2.50
m. Each beam consisted of 34 nos. of strands (tendons)
conforming to class-2 of IS:14268 with UTS of 1900 N/mm 2 .
Each strand of 15.2 mm dia was made up of 7 wires with 6 wires
surrounding the centre wire configuration resulting in
enhanced bond characteristics due to Hoyer’s effect, with net
strand cross sectional area of 140 mm 2 .
The key factors in the choice and capacity of
pretensioning bed was the availability of time for precasting
girders and the economical considerations. The cost benefit

152
analysis for various capacities of long line pre tensioning bed
was carried out as per the Table 3. Since the expenditure on
three beams casting was found to be economically optimum,
saving almost 15 months, the bed for casting three beams was
chosen, making perhaps the longest pretensioning bench in
the country with the length of 122.5 m, for stressing 115 m long
strands (Fig. 8).
TABLE. 3. COST BENEFIT ANALYSIS OF PRETENSIONING BENCH
HEGGADE, MEHTA & PRAKASH ON
Fig. 7. Debonding arrangement for stands at the ends
The largest long line prestressing bed had its own share of
problems. Each strand was to be stressed to 21 tonnes,
warranting the capacity of the pretensioning bench to (2x34) =
714 tonnes. It is essential to design the pretensioning bed to
additional 20 per cent capacity as the prestressing force on
reaction abutment (Fig. 9) will increase due to “long line bench
effect” after casting of concrete, due to shrinkage and
temperature variation between the duration of casting of
concrete and detensioning. Prior to detensioning in the casting
yard, the strands can be stressed up to 0.80 UTS. Due to the
shrinkage of concrete clubbed with reduction in temperature,
shrinks the concrete along with the strands in the bonded length
thereby elongating and inducing further stress in the unbonded
length. If the increase in stress in unbonded length before
Fig. 8. Pre tensioning bench of 122.5 m, for stressing 15 m long strands

Fig. 9. Cross section of Bulkhead
detensioning is beyond UTS, the strands in some cases may
even start snapping, as happened in Sutlej Bridge. The increase
in the stress of the unbonded tendon is directly proportionate
to the ratio of the length of the embedded strands to that of
total strand length. This is also affected by curing time and is
more severe when the ambient temperature during stripping is
low.
The key decisive factors in the choice of formwork for
pretensioned girders were:
(a) High resistance to damage due to rough handling.
(b) The precise dimension of the panels to fit together to
form a large unit with ease.
(c) Cleaning, setting, adjusting and handling ease.
(d) The ability of erecting one side independent of other.
(e) The ability to withstand the form and other vibrations.
(f) Rigid structural soffit form to secure and hold the side
form without movement during concreting.
(g) The minimum joints, which can be tightly sealed to
avoid leakage and bleeding.
The shuttering panels of 3 m length were erected using
8-ton capacity hydro crane, which was supported on ground
anchors by turnbuckles. After erection of one face of
shuttering the alignments to the precision could be carried out
by adjustments of turnbuckles. After the erection of one face
of shuttering the alignment to the precision could be carried
out by adjustment of turnbuckles. After the erection of one
DESIGN AND CONSTRUCTION OF PRE-TENSIONED SUTLEJ BRIDGE IN PUNJAB
153
shuttering face, the reinforcement cages fabricated in three
pieces of 11 m each were shifted to casting bed by hydro
crane. The cages were suitably stiffened by diagonal bars
during transportation, which were removed once placed in
position in casting bed.
HT strands were cut to 115 m length and stacked over
raised platform along the line of casting bed. While opening
the coil, HT strands were passed through water tank to
remove protective coating. The cables were threaded manually
inserting through 20 mm dia ‘PVC’ pipes of required length
meant for debonding. After fixing up the anchorages, the
cables were prestressed from stressing end in predetermined
sequence. The debonding pipes were positioned and sealed
with epoxy and tapes as per the drawing after the stressed
cables were anchored. The other face of the shuttering was
then lifted up and connected to already erect face by 16 mm
through bolts. The gaps were filled with foams for preventing
leakage and one end of the shuttering was provided with 50
mm wooden packing and thermo coal to facilitate easy removal
of shuttering after concreting.
The concrete produced by batching plant of capacity 30
m 3 /hr as per the design mix (Table 4.) transported through a
lead of 100 m by tractor trolley. As the concrete was to be
placed at height of 3.5 m from supply level a mechanical mode
was devised for placement. The device consisted of an
automatic conveyor designed and fabricated (Fig. 10) at site
in such way that it could move on a track line parallel to
pretensioning bed, receive concrete from trolleys up to 0.50
m 3 at a time, carry the concrete through conveyor for 3.50 m
height and deliver to tremie for placement through funnel. The
device could be electrically operated by operator seated on
it, and reduced the concreting cycle to 2 hours from manual
concreting cycle of 5 hours. The concrete compaction was
achieved by poker and shutter vibrators.
TABLE 4. DESIGN MIX DETAILS
The transfer of prestress was induced by cutting strand
by acetylene torch in a pre-decided sequence after concrete
achieved the strength of 31 MPa. The best cycle time achieved
in the beam casting was 66 hours though on a average time

154
Fig. 10. Mechanical device for concrete placement
cycle was 72 hours with the individual activity break-up as
shown in Table 5.
TABLE 5. CYCLE TIME FOR BEAM CASTING
Despite the unforeseen impediments like non-availability
of stacking facilities, repairs of shuttering panels, maintenance
of bed alignment, and rain, etc. the casting of 138 nos. of
beams were completed in 320 days.
The pretensioning can be done either by stressing each
tendon individually or all together at a time. As the stressing
individually called for monostrand jack of 25 T capacity with
a stroke 1000 mm, the individual stressing of strands was
resorted to.
8. BEAM ERECTION
The transportation and erection of beams were
accomplished (Fig. 11) by 3 pairs of side shifting trolleys, a
pair of motorised longitudinal trolleys and a pair of 35-toon
capacity bed gantries. The side shifting trolleys were used
to shift the beams from casting bed to stacking yard and from
there to longitudinally motorised trolleys with the help of
jacks. The longitudinal trolleys being designed at lower levels,
the beams brought by side shifting trolleys were lowered to
HEGGADE, MEHTA & PRAKASH ON
longitudinal trolleys.
To facilitate the movement of bed gantries and
longitudinal trolleys, the track line is laid on wooden sleepers
at 0.70 m c/c as per railway specification over well-prepared
compacted embankments. The motorised trolleys were moved
up to the span where beam was to be erected. The gantries
were used at the location to lift, side shift and lowering of
beam on pedestal as depicted in the Fig. 12 & 13. The lifting
was done with the aid of 750 mm stroke hydraulic jacks and 16
m long suspenders. The side shifting was done using the crab
assembly and winches set on top of gantries. Prior to the
lifting of the beams, the bearings were fixed at the soffit of
beams with sleeves already embedded during concreting. The
surface irregularities were dealt by application of 2 mm thick
epoxy over the bearings. The lowered beams were rested at
about 20 mm above the pedestal and the recess was grouted
using non-shrink cement grout. Till the time the recess was
grouted and end diaphragms were cast, the beams were placed
on wooden sleepers and held by temporary bracings.
On an average 5 hours cycle was comfortably achieved
as shown in the Table 6. with the progress of 3 beams per day
on a regular basis.
TABLE 6. CYCLE TIME FOR BEAM ERECTION
In the water spans, between A/R to P8 and P10 to A/L, the
bed gantries and longitudinal trolleys were moved on railway
track over specially constructed embankments with the
provision of hume pipes at suitable intervals for passing the
water from u/s to d/s. However, not to constrict the water in a
too narrow passage, a temporary service bridge was made on
both sides of the piers to move the bed gantries between P8
and P10. This temporary bridge had single-line of piling on d/
s side to cater for the movement of one leg of the gantry where
as on upstream side two lines of piles were provided to move
longitudinal trolleys and transport other materials.

Fig. 12. Showing the Erection scheme of Beam
Fig. 13. Erection, side shifting & placement
The single line of piles on downstream side was collapsed
during floods when the erection was in progress between P7 &
A/L on Nakodar side. However, on Jagraon side the gantry
was to be brought back to erect the beams on unfinished span
A/R-P22. Among the alternatives considered, providing a
DESIGN AND CONSTRUCTION OF PRE-TENSIONED SUTLEJ BRIDGE IN PUNJAB
Fig. 11. Casting Yard Layout for Sutlej
155
trolley on top of the deck slab and supporting half of the gentry
(Fig. 14) on it proved to be safe, economical and fastest solution.
This method was adopted for shifting both the gantries across
P8 & P10 in seven days time without any risk and just taking
care by dropping plumbs at four locations on both sides of the
gantry to check the evenness of the movement.
Fig. 14. Transportation of gantry on deck
9. BEARINGS
POT and POT-cum-PTFE bearings were used in the Sutlej
Bridge. The typical bearing layout adopted in the bridge is
shown in the Fig. 15. Earlier, normally for the simply supported
bridges up to two lanes, fixed bearings (rocker) with a small
play provision on one end and free bearings (roller) in the
longitudinal direction having fixity in transverse direction has
been successfully used for straight superstructure like Sutlej
bridge. This arrangement for bridges with small deck width can

156
be still successfully adopted as expansion/contraction taking
place in pier caps and diaphragms connecting the superstructure
are same. Nevertheless, to avoid the transverse restraint likely
to be caused by thermal effects and wind force, a typical semi
classical bearing arrangement as shown in the layout was
adopted in Sutlej Bridge. As could be seen from the layout,
there were two types of bearings in span and these two types
of bearings might have different plate sizes and bolting
locations, depending upon the forces, rotations and movements.
In the precast construction like Sutlej Bridge, the grooves have
to be left in the beams at the bolting locations and as such the
manufacture of the bearings have to be approved prior to the
precasting of beams. Normally, the approval of bearing
manufacture is a very high lead-time item, which was well
synchronised in this project. At each pier location for a span,
two central bearings were fixed which were guided
longitudinally on the other side, where as two extreme girders
on either side were transversely guided while on other side left
free. This semi classical layout helped in reducing the types of
bearings to suit the precast construction.
HEGGADE, MEHTA & PRAKASH ON
Fig. 15. Bearing configuration for Sutlej bridge
10. LOAD TESTING OF SUPERSTRUCTURE
In line with the contract agreement, one of the spans was
to be validated by load testing to the designed IRC loading,
including impact factor. As shown in the Fig. 16 the IRC loadings
were simulated for the maximum moments in the midspan
including cycle track loadings. All the pedestals were
progressively and simultaneously loaded by progressive
increments of 25 per cent of the test load and the deflections
were recorded at the midspan of all girders and and ¼th
span of the third girder from left side. The maximum load was
sustained for 24 hours; during the period deflection readings
were taken at one-hour interval for the sustained loading. Then
the unloading was simultaneously carried out in 25 per cent
decrements with the readings taken during each decrement.
The deflection readings of unloaded structure continued at
one-hour interval for further 48 hours.
For each stage of loading and unloading, the observations
were made about the likely appearance of cracks, the linearity
of the load deflection curves or any other abnormalities in the

load deflection behaviour. It was ensured that the bearings are
functional by measurement of rotation.
The deflection measurements were done by suspension
wire method at the required locations using dial gauges. In this
method stools were embedded in firm ground and dial gauges
of least count of 0.01mm were clamped to them. The spindles
of the dial gauges were connected by a pair of adapters in
plumb line with GI wire. To eliminate the effects of temperature,
the deflection readings were taken at fixed timings for all the
operation of loadings and unloading.
The maximum observed deflection for G3 girder at midspan
was 5.35 mm vis-à-vis maximum theoretical deflection of 7.3
mm, with the percentage recovery of 94.95, calculated as per
IRC: SP-51.
11. SUMMARY AND CONCLUSION
Precast pretensioning technology up to the span of 50 m
for river bridge decks can be economically exploited due to its
material efficiency. The following design and construction
aspects deserve special mention in the context of Sutlej Bridge.
1. Design aspect
(a) Separate guidelines applicable to pretensioned
concrete in IRC:18; Universally, there are no separate
codes for post tensioning and pretensioning as the
majority of the aspects of prestressing are applicable
DESIGN AND CONSTRUCTION OF PRE-TENSIONED SUTLEJ BRIDGE IN PUNJAB
Fig. 16. Load Testing of Super Structure
157
to both pretensioned and post tensioned concrete.
However, there is an urgent need to modify the IRC:
18 which is meant only for post tensioned concrete
bridges, to be applicable to both types of prestressing
by giving separate design parameters, such as time
dependent loss criteria, transmission length for
pretensioning, permissible stresses, etc. wherever
relevant and applicable.
(b) Lateral stability for long span prestressed, precast
beams; the guidelines for ensuring the lateral stability
given in the codes are based on steel and RCC beams.
Apart from span to depth and depth to top flange
width ratios, the three independent factor of safeties
i.e. (i) the factor of safety with respect to rotation
against tidal instability for the nearly perfect beams,
(ii) the factor of safety with respect to rotation with
casting imperfection (iii) the factor of safety vis-à-vis
the maximum rotation permissible has to be
established, with due recognition of prestressing
effects.
(c) ‘Long line bench effect’ for pretensioning and ‘Hoyer’s
effect’ for transmission length;
(d) Well cap at the level of LWL/GL to facilitate quality
construction; Providing well cap below the ground
level by 3 to 5 m will only enhance construction
difficulties and does not serve any aspect of good
engineering practice.

158
2. Construction aspect
(a) Provision of track-line for gantries as proper
embankment in the river bed;
(b) Provision of temporary Service Bridge across the river;
(c) Mechanisation of concreting for pretensioned beam.
(d) Use of large panel formwork for piers and beams;
(e) Bearing configuration, fixing of bearings and
stabilisation of beams after the erection till the casting
of diaphragms and deck slab;
Many of the above design and construction aspects
warrant in depth knowledge and meticulous micro planning to
suit the adoption of particular type of technology.
3. Proposal for codal guidelines for pretensioning
On the basis of designing and executing long span
pretensioned bridge spans, the authors propose the following:
(a) The minimum dimensions of the cross section shall
be
(i) Thickness of top flange: 100 mm
(ii) Thickness of bottom flange: 150 mm
(iii) Thickness of web: 150 mm
HEGGADE, MEHTA & PRAKASH ON
DESIGN AND CONSTRUCTION OF PRE-TENSIONED SUTLEJ BRIDGE IN PUNJAB
(b) The span to depth and depth to width ratios for
optimum beam cross section from lateral stability
considerations shall satisfy following Factor Of
Safeties
(i) FOS with out casting imperfections > 2
(ii) FOS with initial imperfections > 1.5
(iii) FOS with Actual angle of tilt > 1.1
(c) Provided adequate un-tensioned reinforcements are
designed for pre cast girder, the tension shall be
permitted at the top fibre of the girder which may be
restricted to 0.36(Fck) 0.5 .
(d) The losses due to seating and friction are not
applicable to pre tensioning. The elastic shortening
loss shall be considered for a condition that all strands
are stressed at the same time and pre stress transfer to
concrete is simultaneous. In case of pre tensioned
girders relaxation losses start as soon as pretensioning
is carried out, but the effect of which is transferred to
concrete at the time of pre stress transfer due to which
relaxation losses calculated as per IRC:18 shall be
divided by 2 for assessment of actually available pre
stressing force at transfer. It is not necessary to
consider 20 per cent additional time dependent losses
for pre-tensioned girders.
(e) Transmission length due to ‘Hoyer’s effect’ shall be
considered to be 30 times the diameter of tendon.
(f) Pre tensioning bench for long line casting shall be
designed for 20 per cent additional capacity to
overcome ‘Long Line Bench Effect’.
ACKNOWLEDGEMENTS
The authors would like to place on record the sincere thanks
to honourable Managing Director, Joint Managing Director,
Chief Engineer and his colleagues of Punjab Infrastructure
Development Board (PIDB) without whose cooperation,
guidance and encouragement, the successful completion of
this bridge would not have been possible. The authors would
also like to thank all the engineers at H.O. and site of Gammon
India Limited for their monumental efforts to construct such a
large bridge within a very short period.