Making of Bandra Bridge

8/19/2019 Making of Bandra Bridge

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Making of Bandra-Worli SeaLink

A triumph of precision engineering

Introduction The Bandra-Worli Sea Link (BWSL) is a civil

engineering marvel spanning an arc of the Mumbai coastline. With

its cable-staed to!ers soaring gracefull sk!ards" the sea link is a

reflection of the modern infrastructure that Mumbai is adding in its

progress to!ards becoming a !orld-class cit.

The BWSL pro#ect is a part of the Western $ree!a Sea %ro#ect"

!hich" in turn" is a part of a larger proposal to upgrade the road

transportation net!ork of greater Mumbai. &n the first phase it !illconnect Bandra to Worli !hereas in the subse'uent phases the plans

are to take it further to a#i li and then to *ariman %oint. &t is a

connecting bridge linking the cit of Mumbai !ith its !estern

suburbs and has the potential to bring about permanent and far

reaching changes in the travel patterns of the area. The Bandra-Worli

Sea Link is primaril meant to provide an alternative to the Mahim

+ause!a route that is presentl the onl connection bet!een South

Mumbai and the Western and +entral suburbs. The pro#ect startsfrom the interchange at Mahim intersection" i.e. intersection of


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Western ,press igh!a and S!ami ivekanand /oad at the

Bandra end" and connects it to 0han bdul 1affar 0han /oad at the

Worli end. The pro#ect has been commissioned to offer a 'uicker

alternative to the north-south traffic that presentl amounts toapproimatel 234"555 cars a da. The pro#ect has been

commissioned b the Maharashtra State /oad 6evelopment

+orporation Ltd (MS/6+) and the Maharashtra 1overnment and is

being built b ++ (industan +onstruction +ompan). s a

builder of landmark infrastructure pro#ects around the countr" ++

has handled numerous challenges both in terms of location and

technolog. The BWSL pro#ect offered ++ an opportunit to

accomplish one more feat7 to construct an eight-lane free!a over the open sea for the first time in &ndia. Highlights in brief 8 &ndia9s

first bridge to be constructed in open-sea conditions

,pansion #oints are provided at each end of the units. The

superstructure and substructure are designed in accordance !ith &/+

codes. Specifications conform to the &/+ standard !ith

supplementar specifications covering special items. The foundation

consists of 2.4 meters diameter drilled piles (: nos. for each pier)!ith pile caps. Bridge bearings are of 6isc Tpe.

The bridge has been built utilising the concept of %re-+ast" post-

tensioned" segmental concrete bo girder sections. n overhead

gantr crane !ith self-launching capabilit is custom built b the

compan to la the superstructure of the precast segments. The %re-

+ast segments are #oined together using high strength epo glue

!ith nominal pre-stressing initiall. The end segments ad#acent to

the pier are short segments ;cast-in-situ #oints


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Bandra channel is >55 meters in overall length bet!een epansion

#oints and consists of t!o 345-meter cables supported main spans

flanked b 45 meters conventional approach spans. centre to!er"

!ith an overall height of 23? meters above pile cap level" supportsthe superstructure b means of four planes of cable sta in a semi-

harp arrangement. +able spacing is >.5 meters along the bridge deck.

The cable-staed portion of the Worli channel is =45 meters in

overall length bet!een epansion #oints and consists of one 245

meters cable supported main span flanked b t!o 45 meters

conventional approach spans. centre to!er" !ith an overall height

of 44 meters" supports the superstructure above the pile cap level b

means of four planes of cable sta in a semi-harp arrangement.+able spacing here is also >.5 meters along the bridge deck. The

superstructure comprises t!in precast concrete bo girders !ith a

fish bell cross sectional shape" identical to the approaches. tpical

%re-+ast segment length is =.5 meters !ith the heaviest

superstructure segment approaching 2:5 tons. Balanced cantilever

construction is used for erecting the cable supported superstructure

as compared to span-b-span construction for the approaches. $or

ever second segment" cable anchorages are provided. total of 3>: cable stas are used at Bandra channel !ith cable

lengths varing from approimatel ?4 meters minimum to nearl

345 meters maimum. The to!er is cast in-situ reinforced concrete

using the climbing form method of construction. The overall to!er

configuration is an inverted ;@< shape !ith the inclined legs

oriented along the ais of the bridge. To!er cable anchorage

recesses are achieved b use of formed pockets and transverse and

longitudinal bar post-tensioning is provided in the to!er head toresist local cable forces.

total of 2>5 cable stas are used at Worli channel !ith cable

lengths varing from approimatel =5 meters minimum to nearl

?5 meters maimum. Like the Bandra channel" the to!er here is also

cast in-situ reinforced concrete using the climbing form method of

construction but the overall to!er configuration is ;&< shape !ith the

inclined legs. Similarl" to!er cable anchorage recesses are achieved

b use of formed pockets. The foundations for the main to!ercomprise 3 meter-drilled shafts of 34 meters length each. +offerdam


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and tremie seal construction have been used to construct the si-

meter deep foundation in the dr. Part – III South End approach

structure This portion of the bridge is similar to the *orth end

approach structure in construction methodolog !ith span b spanmatch cast concrete bo girder sections. Toll Plaa modern toll

plaAa !ith 2> lanes is provided at the Bandra end. The toll plaAa is

e'uipped !ith a state-of-the-art toll collection sstem. structure is

provided at this location to house the control sstem for the &TS.

Intelligent Bridge System The toll station (T%) and collection

sstem !ill provide for three different tpes of toll collection" as

follo!s7

- $ull automatic sstem7 ,lectronic pament through n boardCnits mounted on the vehicles !hich allo! passage !ithout

stopping.

- Semi-automatic sstem7 ,lectronic pament through a smart card"

!hich allo!s pament !ithout having to pa cash.

- Manual toll collection7 %ament of toll b cash" re'uiring vehicle

drivers to make cash pament to a toll attendant" and stopping for

cash echange. The intelligent bridge sstem !ill provide additional

traffic information" surveillance" monitoring and control sstems. &tcomprises ++Ts" traffic counting and vehicle classification

sstem" variable message signs" remote !eather information sstem

and emergenc telephones. The control centre located near the toll

plaAa is housed !ith the electronic tolling controls. The transmission

sstem comprises fibre-optic cable housed in %+ conduits running

parallel to the Bandra-Worli corridor. &n addition" facilities to assist

enforcement are provided in the form of pull-out locations" !hich

!ill allo! drivers and enforcement officers to safel pull-out oftraffic. Po!er Supply "istribution and #oad $ighting System

reliable and dependable po!er suppl has been arranged for the

entire pro#ect. &t !ill also house diesel generator sets and auto mains

failure panels to cater to critical load" e.g." monitoring" surveillance

and communication e'uipment emergenc services like aviation

obstruction lights. de'uate levels of lighting levels have been

maintained and energ saving luminaries has been installed. Special

emphasis has been given to incorporate lighting protection at bridgeto!er and control room building to protect those buildingD structures


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and the sophisticated monitoring and communication e'uipment

installed therein. +hallenges encountered during eecution of the

pro#ect ,ngineering challenges BWSL %ro#ect is a uni'ue and

pleasing structure" but before undertaking the construction"follo!ing !ere the ma#or challenges to be addressed7-

8 The foundations of the bridge included >5: large diameter shafts

drilled to lengths of >m to =:m in geotechnical conditions that

varied from highl !eathered volcanic material to massive high

strength rocks.

8 The superstructure of the approach bridges !ere the heaviest spans

in the countr to be built !ith span-b-span method using overhead

gantr through a series of vertical and horiAontal curves.8 one-of-its-kind" diamond shaped 23?m high concrete to!er !ith

flaring lo!er legs" converging upper legs" unified to!er head

housing the stas and a throughout varing cross section along the

height of to!er.

8 ,rection of 35555 MT Bandra cable-staed deck supported on sta

cables !ithin a ver close tolerance of deviations in plan and

elevation.

The challenges !ere varied and started right from the %re-+ast ard.1round stabilisation for %re-+ast @ard The %re-+ast ard is located

on reclaimed land. The ard caters to casting" storing and handling

of pre-cast segments for the pro#ect totalling 3=:3 in numbers. The

storage capacit re'uirement of ard is to be about :E5nos. s the

area available is limited" the segments are to be stored in stacks of

three laers. The bearing capacit of the ground is of paramount

importance to enable three-tier storage of segments. s the pre-cast

area is on reclaimed land" the bearing capacit of eisting ground!as ver poor and found to be less than 3 TDS'm.

ence detailed ground stabiliAation !as carried out" !hich involved

follo!ing7

8 ,cavation of the ground to a depth of F 3.4Mtrs.

8 Strengthening the ground using rubble soling and filling the voids

!ith sand. The soling thus done !as compacted laer b laer using

vibrator rollers.

8 Total area of the %re-cast @ard !as covered !ith a laer of %++.8 /++ $ooting done to facilitate storing of segments.


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These measures offered the re'uired strength to the casting ard.

%arine !or&s 'oundation and substructure The foundations for

the BWSL pro#ect consist of 3555-mm diameter piles numbering

235 for the cable-staed bridges and 2455-mm diameter pilesnumbering :?: for the approach bridges. The pro#ect9s site geolog

consists of basalts" volcanic tuffs and breccias !ith some

intertrappean deposits. These are overlain b completel !eathered

rocks and residual soil.

The strength of these rocks range from etremel !eak to etremel

strong and their conditions range from highl !eathered and

fractured" to fresh" massive and intact. The !eathered rock beds are

further overlain b transported soil" calcareous sandstone and thin bed of coarse grained conglomerate. The top of these strata are

overlain b marine soil laer up to Gm thick consisting of dark

bro!n clae silt !ith some fine sand overling !eathered" dark

bro!n basaltic boulders embedded in the silt. The ma#or engineering

problems that needed suitable solutions before proceeding !ith the

!ork !ere as follo!s7

2. ighl variable geotechnical conditions of the foundation bed as

eplained above.3. ighl uneven foundation bed even for plan area of one pile.

=. %resence of &ntertidal Hone ($oundation Bed eposed in lo! tide

and submerged in high

tide).

The ke to success !as a program of pier b pier in-situ testing. n

etensive subsurface eploration and drilling program (total 2G2

bores inside sea) !as undertaken to define the subsurface

stratigraph" determine the rock tpes and obtain material propertiesfor optimiAing the foundation design. !ing to a highl variable

geolog" the design calculations !ere performed on a pier-b-pier

basis and the unit side

shear values !ere checked that the did not eceed the load test

results under similar rock conditions.

The !orking load on the approach piles ranges from E55 tons to

2455 tons !hereas for the piles belo! the cable-staed bridge

!orking load


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is 3455 tons. $or conducting the

load test on the piles" the load to be applied varied from :455tons to

G>55tons.

rranging reactions for such loads either b normal kentledgemethod or b soil anchor re'uired massive scale arrangements in the

sea !aters. This !as completel avoided b a careful planning of

load

test using the sterberg load cell method (/efer sketch 2).

The a!ard !inning sterberg +ell" or ;-+ell9" gets its name from

the inventor" 6r. Ior# . sterberg. The -cell is a hdraulicall

driven" high capacit" sacrificial loading device installed !ithin the

foundation unit. Working in t!o directions" up!ard against side-

shear and do!n!ard against end-bearing" the -cell automaticall

separates the resistance parameters. B virtue of its installation

!ithin the foundation member" the sterberg +ell load test is not

restricted b overhead structural beams and tie-do!n piles. &nstead"

the -+ell derives all reaction from the soil andDor rock sstem. ,nd

bearing provides reaction for the skin friction portion of the -+ell

load test" and skin friction provides reaction for the end bearing

portion of the test. Load testing !ith the -+ell continues until one


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of three things occurs7 ultimate skin friction capacit is reached"

ultimate end bearing capacit is reached" or the maimum -cell

capacit is reached.

,ach sterberg +ell is speciall instrumented to allo! for directmeasurement of the end bearing and skin friction. -+ells range in

capacities from 5.E M* to 3E M*. B using multiple -+ells on a

single horiAontal plane" the available test capacit can be increased

to more than 355 M*. t BWSL" four test locations !ere selected

for the follo!ing criterion.

/everse +irculation 6rilling method is adopted for foundation

construction. The highl uneven foundation beds and the presence of

intertidal Aone brought in lots of difficult in terms of Liner pitching.This problem !as solved b constructing a gabion boundar at the

bed level around the casing" pouring concrete bet!een the casings to

make an artificial penetration of the casing. fter setting of the

concrete under the !ater" drilling !as commenced using /+6.

&t is interesting also to mention that loss of !ater head during

continuous drilling operation !as a ma#or problem !hile !orking in

the intertidal Aone. This !ater head loss leads to ver slo!

production rate and ver high consumption of drill bits. To overcomethis problem" pits

!ere made in the lo! tide at each foundation location using an

,cavator and the casing !as placed at the bottom of the pits. Then

the casing !as placed in the pits and !as concreted to make an

artificial penetration" maintaining the proper !ater head for

continuous drilling.

$or several locations" cofferdam construction using steel liner and

sheet piles !as not possible due to ver hard and uneven strata. erethe problem !as solved using circular steel caissons. These caissons

!ere fabricated outside and to!ed to location using -frame barge.

The caissons !ere sunk at the location using counter!eights. The

unevenness at the bottom !as sealed using the gabion method. The

benefit of this method !as that it completel eliminated deploment

of resources like Iack up %latform" +rane" ibrohammer"

+ompressor" etc. for liner pitching. &t also eliminated substantial

amount of field !orks and is pre-fabricated in principle.


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Superstructure The BWSL %ro#ect has (GK3) approach bridge

modules. These modules range from = continuous span units to ?continuous span units. The deck of the carriage!as consists of

triple cell precast bo girders supported on piers founded on

independent substructure. The +oncrete 1rade for the superstructure

is M>5. The average !eight of the span is 2?55 tons" !hereas the

heaviest span in the bridge (to be erected !ith the Launching

1antr) !eighs 3555 tons. &n addition" the trusses !ere to be

designed to receive the segment from the alread erected deck as

!ell as from barges parked directl under the truss.The Technical 6ata for the superstructure is as follo!s.

Ma Longitudinal 1radient 2.E3

Ma +rossfall >

Ma /adius in %lan >55m

Min /adius in %lan 3:>m

Tpical Span Length 45m and =5m in Link Bridge

Ma Span Weight 3555 tons

The erection gantr is 23>5MT truss designed to erect spans for theabove configuration. The uni'ue feature of the truss indeed is the


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maimum span !eight it can handle and that it can launch the pier

and ,I segment itself. The truss also has the capacit to align the

total span in hanging condition after the gluing is completed. The

truss is full mechaniAed for self-launching and aligning. n

individual segment can be aligned on the truss using a set of four

hdraulic #acks mounted on each suspension frame. &n order to

eliminate the casting or erection errors !ithin a span" t!o !et #oints

are provided on either end of the span. The !et #oints are cast after

finaliAation of the span alignment.

$or the fabrication of the truss" the entire structural steel (grade $e

4:5) !as sourced from !ithin &ndia. The accessories and

components ho!ever !ere procured from &ndia and abroad.

full scale load test !as conducted before putting the erection

gantr into actual operation.

The erection gantr comprises the follo!ing7

a. Main truss

b. $rontDrear plons

c. $rontDcentreDrear legs

d. $ront Drear trolle

e. +ross beamsf. Stressing gondola

g. Suspension frames

h. +onnection beams-Tpe DB

i. Spreader beams- Tpe DB

#. %ier bracket

k. +hain Support

Tpical 45m span of the approach bridges comprises 24 field

segments" a %ier segment and 355mm (nominal) in-situ !et #oints.6uring the span construction" all field segments are suspended from

the 1antr" glued and temporaril stressed together. nce the gluing

operation is completed" span alignment to the %iers is follo!ed.

fter alignment" the !et #oints are cast including grouting of

bearings top plinth. nce the !et #oints achieve the re'uired

strength" stressing of longitudinal %T is commenced follo!ed b

Load transfer of Span to %iers.


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.

/elocation of Launching Trusses using 2>55MT capacit Barge

Mounted +rane J sian ercules fter the successful erection of the

deck on Bandra side" the trusses !ere re'uired to be shifted across

the Bandra cable sta bridge b >55 meters to Worli side to take up

the spans

beond the Bandra +able Sta.

arious options like (i) dismantling of the trusses at present locations

and reassembling them at ne! locations" (ii) lo!ering the trusses on

a suitable floating craft and shifting and erecting them" and (iii)

shifting the total truss using a floating crane" etc. !ere analsed in

detail.

Taking into consideration various constraints like limited !orking

period available to eecute the !ork in sea" the effect of open sea on

dismantling and re-erection" etc." the best option available !as the

relocation of the trusses in one piece using a floating crane.

sian ercules is one of the biggest floating shear leg cranes in the

!orld. This crane is mounted on a barge !hich is over 3:5 feet long

and more than 2=5 feet !ide" !eighs 4"G55 tons and has enough

lifting capacit (2>55 MT) to lift a !eight e'ual to 3"555 small cars.

&t

started its voage from Singapore on ctober G" 355>" and arrived at

Mumbai9s shores on ctober 3E" 355>. fter obtaining the necessar

regulator clearances" it commenced operations from *ovember 5>"

355>" including trial runs and realignments in its settings.

Selection of e'uipment !as done considering various challenges"


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like the draft and space available at !orking locations" tide

limitations" and other !eather constraints. The process7 The biggest

hurdle on the sian ercules operation !as that the draft at the

re'uired locations !as not good enough to carr out the operation

smoothl !ithout disturbing the S*L cable ling underneath. This

problem !as overcome b using sophisticated global positioning

sstem and carring out the entire operation in a series of

smaller operations during the favourable high-tide. $irst the sian

ercules +rane !as positioned at the re'uired lifting position.

comple operation of balancing the vessel using ballasting !as

carried out as per the predetermined stages. %ositioning of the vessel

!as done considering the draft re'uirements. speciall fabricated

lifting spreader !as fied to the truss to facilitate the lifting.

The truss load !as taken b the crane in stages so that the lifting

operation !as smooth.

Through computeriAed central monitoring" the load in individual

lifting points !as monitored to ensure that no point !as overloaded.

fter taking the load" the sian ercules crane !as moved to a safe

location !here enough !ater depth (draft) !as available to park the

crane !ith the truss. Then the crane !ith the truss !as moved to a

ne! location during the net high tide. The truss !as then lo!eredon to the final location. The lo!ering of truss at the final location

!as achieved through 1uides" !hich helped to achieve a final

placement accurac of N45mm. The operation" !hich other!ise

!ould have taken one complete ear" !as completed in matters of a

fe! das. Cable Stay bridges &t is for the first time that cable sta

bridges have been attempted on open seas in &ndia.


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+oupled !ith the fact that the aestheticall designed plons have an

etremel comple geometr and one of the longest spans for

concrete deck" the challenges encountered !ere indeed formidable.

+onstruction of %lon To!er Legs

The salient characteristics of the plon to!er that make it comple

and challenging from the point of vie! of constructabilit are as

follo!s7

(a) The section decreases graduall !ith heightO

(b) There are horiAontal grooves at ever =m height and vertical

grooves for circular portion that re'uires special form liners as !ellas it re'uires attention for de-shutteringO

%&,/ TBL,

+BL, *+/ H*, 25

L&$TS

C%%,/ TW,/ L,1S 3:

L&$TS

LW,/ TW,/ L,1S ?

L&$TS


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S&6, &,W $ TW,/ %2G $/ B*6/ +BL,-ST@,6

B/&61,

(c) The to!er legs are inclined in t!o directions" !hich creates

compleities in alignment and climbing of soldiersO(d) +onstruction #oints permitted onl at =m level. &nserts !ere

permitted onl in horiAontal grooves provided at =m height.

n not being able to get immediate solution from reputed !orld!ide

form!ork manufacturers" the pro#ect design team designed an

automatic climbing shutter form!ork sstem" !hich !as fabricated

on site and emploed to eecute all to!er leg lifts belo! deck level.

To affect further reduction in time ccles" ++ approached 6oka"

ustria. 6oka then devised a customiAed solution based on theirS0,-255 automatic climbing shutter sstem.

+onstruction of to!er legs belo!

deck level 60 S0,-255 utomatic +limbing Scaffolding

Sstem erected on to!er legs

a. Surve of To!er Legs

The comple plon geometr !as another challenge for surveors.

+oupled !ith geometr" the construction stage analsis indicated

leaning and progressivel increasing in!ard inclination of plon legs

during construction. ++9s %rincipal Surveor devised a

sophisticated technolog to measure coordinates through a

combination of total station and prisms mounted on plon legs. The

temperature and construction stage analsis factors !ere applied to

derive the corrected coordinates. The plon legs !ere constructed


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!ithin an accurac of N4mm" !hich speaks volumes about the

techni'ue emploed.P

b. nchorage Bo

nchorage Bo for Bandra +able Sta Bridge placed on To!eread Iunction nchorage Bo for Worli +able Sta Bridge

nchorage Bo is used as inner shuttering for to!er head. Bearing

plates !ith guide pipes are fied to the anchorage bo. 1uide %ipe

and Bearing %lates actuall transfer the deck loads to to!er concrete

!hich are generated due to stressing of sta cables. The anchorage

bo is fabricated !ith 23mm thick high grade steel plates. &t is

fabricated in pieces and then bolted at to!er head portion. The

bearing plates and guide pipes of anchorage bo are galvaniAed andthe remaining portion !as painted !ith anticorrosive polurethane

based paint.

nchorage boes are fied !ith the help of co-ordinate sstem for

accuratel fiing the anchorage point and angle of sta cable.

c. +ompression struts

+ompression struts are provided at various levels of to!er legs.

These !ere basicall provided to keep the alignment of all to!er

legs in their re'uired position. 6uring construction" due to geometr

it !as possible that the to!er legs might lean in!ards due to !eight

and stresses involved in the base. &n order to avoid that" compression

struts !ere


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provided and #acking done to desired load to maintain the alignment.

d. ,rection of %ier Table segments The pier table segments

numbering :3 for both the carriage!as !ere another hurdle

encountered. The reasons being J (a) Launching Truss could not be deploedO

(b) Being generall over the plon pile cap" lifting segments from

the sea !as not possible. To overcome this hurdle" ++9s ,pat

devised a brilliant and ingenious solution in the form of J

-%ier Table Trusses (%TT)7 ne each !as erected for each

carriage!a. &t had rails on top to move segments !ith the help of

hdraulic #acks from one end to another.

-Lifting $rame7 This !as an ingenious little devise mounted at either end of %TT.

SLC (Strand Lifting Cnits) !ere mounted on top to lift the segment

from barges anchored in the sea. fter lifting the segment" the front

frame closed do!n" !here the segment !as lo!ered on the rails. The

rear frame lifted up to enable the segment to slide across the %TT

hdraulicall.

ST1,7 2

pen the Support Bracket and Lift the Segment. +lose the SupportBracket" Slide in the Trolle and Lo!er the Segment on Sliding

Trolle

ST1,7 3

pening of the Lifting Boom Q Strut" Slide out the Segment and

+lose the Lifting Boom and Q Strut. /epeat operations for the other

segment lifting.

e. ,rection of segments of +able Sta Bridge b 6errick The method

used for erection of segments at +able-Staed bridge !as balancecantilever construction method. 6uring construction" the length of

free cantilever for Bandra +able-

Staed bridge !as 324m and for Worli +able-Staed bridge it !as

E=m. The segments !ere lifted b the instrument named 6errick

!hich !as fied on both ends of the pier table segment and then

for!arded. Lifting operation !as done simultaneousl on both ends.

t a time" 6errick can lift one segment. 6eck is constructed of

alternate sta andnon sta segments #oined to pier table segments.


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Lifting of Segment !ith 6errick

f. 6r Matching" ,po and temporar stressing for gluing When

the segment is positioned" it is to be #oined !ith the eisting

segment. Therefore" the segment !as first dr-matched !ith thealread erected segment. n completion of dr-matching" the

segment !as moved back b sliding the lifting beam for a distance

of :55mm of the derrick and epo !as applied on the face of both

segments. fter application of the glue" the segments !ere #oined

together and !ere stressed b Temporar %T bars. %ost this step" the

segment lifting beam on derrick is moved for!ard to lift the net

segment i.e. sta segment.

g. ,rection of Sta segmentThese segments !ere also erected similarl as the non-sta segment

and !ere also #oined in the similar !a. fter this" guide pipes !ere

installed over the ducts left behind during segment casting.

h. Sta cable

Sta +ables used are R%arallel Wire Sta +ables9. The !ere

manufactured b ;Shanghai %u#iang +able +o. Ltd< +hina. ,ach

cable consists of a group of different number of steel !ires. ,ach

!ire is made up of high tensile steel. 6iameter of single !ire !asEmm !ith a

breaking limit of >.3? Tones. Si different siAes of cables !ere used

in the cable-staed portion. The difference bet!een them !as onl

on the basis of number of steel !ires in each cable. Si different

tpes used !ere of >2" E=" ?4" G2" 25G and 232 steel !ires. 1roup of

these !ires !as packed in t!o laers of 6%, (igh 6ensit %ol

,thlene) material to protect them from atmospheric effects. Typical

Cross Section of Stay Cable i. +losure pour &n Bandra +able-Staed Bridge" closure pour is provided bet!een

main cable-staed cantilevers and back span. &n Worli +able-Staed

bridge" closure pour is provided bet!een t!o cable-staed cantilever

decks

#. Longitudinal stressing and grouting

When all the segments and cables !ere erected" the segments !ere

post tensioned longitudinall. This post tensioning !as done b

stressing the steel tendons placed in the ducts provided inside the bod of segments. This helps the members to sta together and to


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increase their load carring capacit as a large number of segments

!ere #oined together to make single unit. nce the stressing !as

done as per re'uirement" these holes or ducts !ere filled !ith

cement grout and !ere plugged at both ends.k. $ine tuning

fter completion of closure pour and post-tensioning of the deck"

fine tuning of sta cables is done. $ine tuning is fine force

ad#ustments of the sta cables to achieve the re'uired stresses in the

deck and profile of the deck.

6uring fine tuning" forces in the sta cables are ad#usted to suit

further addition of superimposed dead loads such as !earing coat"

crash barriers" handrails and also vehicle loads.6uring fine tuning operation" longitudinal and transverse deck

profiles are also monitored to provide smooth curve.

l. Wearing +oat over south bound bridge deck Bridge deck surface

of south bound carriage!a is provided !ith :5mm thick %olmer

Modified Bituminous pavement in con#unction !ith !ater-proofing

sstem to seal the bridge deck. (or&ing during monsoon The

Maritime Board does not allo! marine traffic in monsoon season.

Thus" !ork !as halted mid-Ma onl to re-commence in ctober"effectivel reducing the !ork schedule to onl seven months in a

ear. To overcome this hurdle and to use this time to speed up the

construction activities at Bandra %lon" ++ put forth the solution

in the form of an innovativel designed temporar bridge. This

bridge had a total length of =34 metres. &t had the facilit of a

!alk!a" a concrete pipe line" an electricall-operated trolle

mounted on rail" !ater line and a pipe line. &t paved the !a for

successful continuation of !ork during the monsoon season !henthe sea !as rough and the !inds !ere strong. $ogistics nother

challenge !as ensuring effective suppl chain at all !orking

locations spread across the alignment in the sea and formulating

measures to ensure the same. diligentl !orked out logistic plan

!as put into action to ensure that commodities !ere handled at

dedicated

location and dispatches monitored meticulousl. State-of-the-art

electronic devices !ere placed on the barges to cut do!n on idletimings.


19/41

6uring peak construction activities" innovative procedures and

specialiAed e'uipment9s !ere re'uired to enable high accurac.

,pert cre!s had to also eercise good #udgement in assessing sea

behaviour and priorities during foundationD substructureconstructions and final

placement of concrete in situ. *avigation and transporting 2G precast

segments in 3: hours at different open sea locations !as a challenge.

Secondl" concrete consumption at the peak had been at the rate of

45cumDhr. Cnder marine conditions" the consumption rate has been

in the order of E55cum per da. To add to this" maintaining ade'uate

food suppl for around 3455 people (in a shift) !orking in the sea at

over =5 locations !as a big challenge. These complete re'uirements!ere met !ith an effective utiliAation of a fleet of =5 marine vessels

including 2= barges for concrete" segments and material transport"

eight steel boats for material and !orkers transport" three tug boats

and si smaller passenger boats.

round four passenger boats !ere used for carring food to

approimatel =5 locations in the sea. ,ach emploee" !hile starting

his da" entered the log indicating the location at !hich the !ould

be !orking. Thereafter began the clock!ork of gathering tiffin boes" !ashing and cleaning" allocation and dispatch as per the log

entries along !ith the drinking !ater suppl including tea suppl at

t!o time intervals per shift. 6uring rough sea conditions in the

normal !orking season" etra tiffin9s !ere carried to take care of

possible spillage !hile

transferring the tiffin9s from boats to !orking locations. Thus

!orkers !ere also suitabl cared for" !hile meeting the engineering

challenges posed during construction of the Bandra- Worli Sea Link.Psychological conditioning With a long track record and

eperienced in building large infrastructure pro#ects" ++ follo!s

strict guidelines for occupational health and safet and environment

protection.

Safet is etremel important to ++ and the compan officials

!orked to!ards sensitising labour and creating greater a!areness of

safet standards !ith gentle persuasion" consistent motivation and

tool bo meetings. The kind of structured processes that !ereimplemented b ++ for ensuring safet is nothing short of


20/41

phenomenal.

Lack of a!areness is the biggest haAard for safet. Since the primar

safet haAard are related to engineering control" e'uipment" #ob

methodolog" material handling" structural fabrication andemergenc preparedness" ++ made sure that ever !orker is taken

through the S, program. The orientation program made them

a!are of the various safet haAards associated !ith a pro#ect and

necessar precautions to be taken to prevent them. The are also

taught ho! to evacuate during an emergenc. $or its meticulous

planning and implementation of safet practices for the BWSL

pro#ect" ++ has !on the prestigious ;1olden %eacock !ard< for

safet" health and environment in Iune 355E. )ey people ver =555!orkers !ere emploed to !ork on the pro#ect. Several teams of

++ engineers and foreign engineers and technicians have been

involved in specialised tasks on the structure of the Sea Link. These

include professionals from +hina" ,gpt" +anada" S!itAerland"

Britain" Serbia" ustralia" Singapore" Thailand" ong 0ong"

&ndonesia and the %hilippines. &n terms of language" cultural

differences and methods of !ork these ke people !ere different" et

the engineering challenges kept the group creativel involved" andthe !orked enthusiasticall as a team.

JFFFFFFFFFFFFJ

*This pro+ect ga,e us an opportunity to sho!case our

euipment.

#a&esh )aul

says #a&esh )aul/ 0eneral %anager/ Elcome Technologies

P,t1 $td1/ !ith reference to the sur,ey euipment that they

supplied for the Bandra-(orli Sea $in&1


21/41

(hen did Elcome Technologies first get associated !ith HCC on

the Bandra- (orli Sea $in& Pro+ect2 Leica e'uipment has been

used on most of the Sea Link pro#ects around the !orld and based on

this eperience !e approached industan +onstruction +ompan(++) sometime at the end of 3555 !ith our range of specialised

e'uipment9s for the Bandra-Worli Sea Link (BWSL). The first Leica

Total Station !as supplied b us to ++ in earl 3552. (hat !ere

the euipment supplied for this pro+ect2 To meet the demand for

high accurac coordinate measurements on the BWSL pro#ect !e

supplied high performance Leica Total Stations including the T+

355=" the T+ 2?55" the T+ 2352" the T+/M 2352 / =55 and the

T+ 2?55. We also supplied the S/ 425 1%S e'uipment. (hat &indof support did you pro,ide HCC ,is-3-,is the euipment that

you supplied to them2 We gave comprehensive application

trainings at their site to!ards effective and optimal usage of the

e'uipment. Moreover" these e'uipment9s in keeping the desired

accuracies that are re'uired for such a pro#ect" needed timel

calibration checks and corrections J for this" besides providing them

complete service support during the !arrant" !e also got into

annual maintenance contracts for these e'uipment post their!arrant period. We !ere thus able to provide timel service and

calibration of the e'uipment at our service centre. "o you thin&

being associated !ith the pro+ect gi,es Elcome Technologies any

le,erage for other similar pro+ects2 &t has been a privilege to be

associated !ith BWSL and the ++ team !e !orked !ith.

Moreover the challenges in geometric control on the pro#ect !ere

highl demanding and eacting. This gave us an opportunit to

sho!case our e'uipment and our epertise. ur eperience !ithBWSL pro#ect !ill be a basis for us to promote our technolog on

other such pro#ects too.


22/41


23/41

Partners in,ol,ed 2. SL Singapore %vt Ltd 7 Technical

+onsultants

3. Cltra Tech7 Supplier of cement

=. Metco group of companies7 Supplier of bearings

:. Tata Steel" /&* Ltd Q S&L7 Supplier of steel

4. ,L0,M &nternational Ltd.7 *or!a-based compan supplier of

micro silica


24/41

>. S%++7 +hina-based compan supplier of sta cable

E. 60 ustralia7 supplier of %lon form!ork

,'uipment used

The ma#or e'uipment9s deploed for this pro#ect are78 Iack up platform" launching truss" reverse circulation drilling

machine floating barrages" boats" cra!ler crane" to!er crane" gantr

crane" derrick crane" placer boom" diesel generators" concrete pump"

transit miers Q R9 frame barrage.

8 The e'uipment !as brought together from various countries.

The construction of the mammoth bridge structure re'uired huge

cranes and other structures to lift material for off shore and on shore

structures. Some of these included72. Launching Truss7 Weighing 2345 tonnes and measuring 223 m in

length" it !as used for lifting segments each !eighing 2=5 tonnes.

This has been fabricated in &ndia.

3. Iack up platform7 SiAe 2?.==53.2m (Width Length 6epth)

having four legs of =5m. &t is a floating e'uipment used for marine

!ork.

=. $lat barge7 SiAe =5233m. Like motor boats" the are driven

inside the sea for material transportation.:. Self-propelled barge7 &t is a barge !ith a machine component and

is used for concrete transportation.

4. +ra!ler crane7 +apacit ranges from E4-245 tons. &t is used for

material and heav lifting activities.

>. /+6 drill bit7 6imension 2.4m 3m diameter. &mported from

0orea" the /+6 drill bit is used for pile drilling !ork.

E. ibro hammer (%T+)7 &mported from $rance and used for driving

of steel liners.?. $ushun cra!ler crane7 &mported from +hina" +apacit ?5 tons.

G. *+0 ,iger crane7 &mported from ,ngland" capacit >4 tons.

25. 0obelco cra!ler crane7 &mported from ong 0ong" capacit 245

tons. 'ascinating facts 8 The pro#ect has alread been acclaimed b

the vie!ers as an engineering marvel of modern &ndia.

8 $irst +able-Sta Bridge in &ndia in open sea.

8 The length of the bridge is >= times the height of the utub Minar

in 6elhi.8 &ts !eight is e'uivalent to 45"555 frican elephants.


25/41

8 The length of the steel !ires used is e'uivalent to the

circumference of the earth.

8 The height of the cable-staed to!er is 23? m" !hich is e'ual to a

:=-store building.8 total of :3: cables !ere used for both Bandra cable sta as !ell

as Worli cable sta bridges.

8 The cables have been sourced from Shanghai %u#ang +able

+ompan" +hina. The cables !ere sub#ect to a series of 'ualit and

engineering tests to meet the special re'uirements including fatigue

tests of t!o million ccles.

8 The cables are made of high tensile steel and are designed to take

the maimum load of G55 tons.8 G3"555 tons of cement !as utiliAed to make BWSL.

8 ,nvironment friendliness !as top priorit during the construction J

fl ash" a !aste product etracted from thermal po!er plants" !as

mied !ith concrete" to make the construction durable as !ell as

eco-friendl" thus making good use of !aste material.

8 The construction team is like a mini Cnited *ations7 several teams

of foreign engineers and technicians have !orked on specialiAed

tasks on the structureO these include professionals from +hina",gpt" +anada" S!itAerland" Britain" Serbia" Singapore" Thailand"

ong 0ong" &ndonesia and the %hilippines" ustralia.

8 The Launching Trusses" each 223 meters long" !ere custom built to

precision b ++ for this pro#ect. The pre-cast concrete segments of

this four-lane road are fabricated at the Bandra site location. These

segments are then carried on a barge to the construction location and

are lifted b the Launching Truss to the designated height and

assembled bet!een t!o piers" each 45 meters apart. $ifteen suchsegments are fitted bet!een t!o piers and the Launching Truss can

lift all fifteen segments together" !eighing 2=5 tons each" bet!een

t!o piers. nce these segments are fied bet!een t!o piers" the

Launching

Truss cra!ls to the net piers on its mechanical legs.

8 1iven the gigantic siAe of the pro#ect" mega e'uipment9s !ere used

in constructionO bringing them to the pro#ect site and operating them

!as a feat in itself. sian ercules" one of the biggest floating shearleg cranes in the !orld" !as hired from Singapore to lift the massive


26/41

2345 tonnes" custom-built Launching Trusses !ith its mechanical

arm and relocate them on the Worli side of the bridge.

industan +onstruction +ompan (++)

2. SL Singapore %vt Ltd7 Technical +onsultants3. Cltra Tech7 Supplier of cement

=. Metco group of companies7 Supplier of bearings

:. Tata Steel" /&* Ltd Q S&L7 Supplier of steel

4. ,L0,M &nternational Ltd.7 *or!a-based compan supplier of

micro silica

>. S%++7 +hina-based compan supplier of sta cable

E. 60 ustralia7 supplier of %lon form!ork Euipment used

The ma#or e'uipment9s deploed for this pro#ect are78 Iack up platform" launching truss" reverse circulation drilling

machine floating barrages" boats" cra!ler crane" to!er crane" gantr

crane" derrick crane" placer boom" diesel generators" concrete pump"

transit miers Q R9 frame barrage.

8 The e'uipment !as brought together from various countries.

The construction of the mammoth bridge structure re'uired huge

cranes and other structures to lift material for off shore and on shore

structures. Some of these included72. Launching Truss7 Weighing 2345 tonnes and measuring 223 m in

length" it !as used for lifting segments each !eighing 2=5 tonnes.

This has been fabricated in &ndia.

3. Iack up platform7 SiAe 2?.==53.2m (Width Length 6epth)

having four legs of =5m. &t is a floating e'uipment used for marine

!ork.

=. $lat barge7 SiAe =5233m. Like motor boats" the are driven

inside the sea for material transportation.:. Self-propelled barge7 &t is a barge !ith a machine component and

is used for concrete transportation.

4. +ra!ler crane7 +apacit ranges from E4-245 tons. &t is used for

material and heav lifting activities.

>. /+6 drill bit7 6imension 2.4m 3m diameter. &mported from

0orea" the /+6 drill bit is used for pile drilling !ork.

E. ibro hammer (%T+)7 &mported from $rance and used for driving

of steel liners.?. $ushun cra!ler crane7 &mported from +hina" +apacit ?5 tons.


27/41

G. *+0 ,iger crane7 &mported from ,ngland" capacit >4 tons.

25. 0obelco cra!ler crane7 &mported from ong 0ong" capacit 245

tons. 'ascinating facts 8 The pro#ect has alread been acclaimed b

the vie!ers as an engineering marvel of modern &ndia.8 $irst +able-Sta Bridge in &ndia in open sea.

8 The length of the bridge is >= times the height of the utub Minar

in 6elhi.

8 &ts !eight is e'uivalent to 45"555 frican elephants.

8 The length of the steel !ires used is e'uivalent to the

circumference of the earth.

8 The height of the cable-staed to!er is 23? m" !hich is e'ual to a

:=-store building.8 total of :3: cables !ere used for both Bandra cable sta as !ell

as Worli cable sta bridges.

8 The cables have been sourced from Shanghai %u#ang +able

+ompan" +hina. The cables

!ere sub#ect to a series of 'ualit and engineering tests to meet the

special re'uirements including fatigue tests of t!o million ccles.

8 The cables are made of high tensile steel and are designed to take

the maimum load of G55 tons.8 G3"555 tons of cement !as utiliAed to make BWSL.

8 ,nvironment friendliness !as top priorit during the construction J

fl ash" a !aste product etracted from thermal po!er plants" !as

mied !ith concrete" to make the construction durable as !ell as

eco-friendl" thus making good use of !aste material.

8 The construction team is like a mini Cnited *ations7 several teams

of foreign engineers and technicians have !orked on specialiAed

tasks on the structureO these include professionals from +hina",gpt" +anada" S!itAerland" Britain" Serbia" Singapore" Thailand"

ong 0ong" &ndonesia and the %hilippines" ustralia.

8 The Launching Trusses" each 223 meters long" !ere custom built to

precision b ++ for this pro#ect. The pre-cast concrete segments of

this four-lane road are fabricated at the Bandra site location. These

segments are then carried on a barge to the construction location and

are lifted b the Launching Truss to the designated height and

assembled bet!een t!o piers" each 45 meters apart. $ifteen suchsegments are fitted bet!een t!o piers and the Launching Truss can


28/41

lift all fifteen segments together" !eighing 2=5 tons each" bet!een

t!o piers. nce these segments are fied bet!een t!o piers" the

Launching

Truss cra!ls to the net piers on its mechanical legs.8 1iven the gigantic siAe of the pro#ect" mega e'uipment9s !ere used

in constructionO

bringing them to the pro#ect site and operating them !as a feat in

itself. sian ercules" one of the biggest floating shear leg cranes in

the !orld" !as hired from Singapore to lift the massive 2345 tonnes"

custom-built Launching Trusses !ith its mechanical arm and

relocate them on the Worli side of the bridge. industan

+onstruction +ompan (++).

JFFFFFFFFFFFFJ

%eeting challenges !ith inno,ation4

Col S "i!an+i

Pro+ect %anager/

Bandra-(orli Sea $in& Pro+ect/

Hindustan Construction Company

satish1di!an+i5hccindia1com

(hen did the !or& on the Bandra- (orli Sea $in& pro+ect

start2 industan +onstruction +ompan (++) !as a!arded

%ackage & of the %ro#ect and !ork started in September 3555" but

!as held up due to several reasons including environmental issues

and protests b fishermen. &n right earnest the !ork started in

6ecember 355:. 6n !hat basis !as the distance bet!een the

piers and the height of the bridge decided2 The span bet!een the

piers is 45m. This distance !as arrived at after considering various


29/41

factors" !hich included optimiAation bet!een the foundation cost vs.

the superstructure cost. &f the piers are !ide apart then the

foundation cost comes do!n" but the superstructure becomes heavier

and its cost goes up.

lso the navigational re'uirements as in an emergenc the smaller

tra!lers and boats should be able to pass bet!een the piers.

Moreover" more number of piers provides better !ind resistance to

the bridge. (hy !as the cable-stayed bridge design chosen for

the Bandra-(orli Sea $in&2 cable staed design has some

inherent advantages compared to other conventional designs" the

main being that it allo!s for larger spans. There !ere three mainreasons !h a large span !as needed in case of the Bandra-Worli

Sea Link7

8 navigational channel for the fishermen and other sea faring

vessels had to be maintained.

8 There are plans to epand the present #ett.

8 There are overseas communication cables on the seafloor !hich

keep shifting and this had to be taken into consideration. At !hatstage of the bridge construction !as the need for precision

sur,ey instruments felt2 We kne! from the start of the pro#ect that

high precision e'uipment !ould be needed and one of the first

things !e did !as to mobilise the Total Stations J the first of !hich

!ere procured in earl 3552.

Sur,ey Challenges4 Bandra (orli Sea $in& Pro+ect

Len 1o!er" %rincipal Surveor on the Bandra-Worli Sea link

%ro#ect for industan +onstruction +ompan" shares his

eperiences on the pro#ect in an eclusive intervie! !ith

+oordinates.

$en 0o!er

len1go!er5gmail1com


30/41

71 'or those of us !ho use them/ a bridge is a bridge8 but for

those !ho build them each bridge has its indi,iduality1 Pleasetell us about some of the bridges that you ha,e !or&ed on in the

last fe! years1 &n the past 25 ears" & have !orked on E long span

bridges. ,ach one posed uni'ue technical challenges that !ere

overcome b m teams.

The /ion ntirrion Bridge" bet!een the %eloponnese peninsula and

the 1reek mainland" is a four plon" 3355 metre span across a

seismic fault in the Strait of +orinth. The plon bases are not fied

to the seabed" but rather rest on an engineered bed of gravel and

inclusion pipe piles. Thus the are free to move during a seismic

event" !ithout sustaining damage. The deck is mounted to the plons

!ith telescopic Rshock absorber9 energ dampers" so minor plon

movement can be accommodated safel.

The %uente de las mericas cable staed bridge spans the %anama

+anal" about 24 km east of %anama +it. The siAe of the ships that

pass through the canal necessitated a ver high navigation envelope beneath the deck" and the commercial ramifications of interrupting

canal traffic meant that the entire bridge had to be constructed

!ithout the use of marine barges or floating cranes. The deck !as

cast in situ !ith movable shutters and one of the largest form!ork

travellers ever utiliAed in bridge construction. The other ma#or

technical challenge !as that the deck erection started before the

plon construction !as complete. This meant that if the deck !as

out of balance for some period of time" the plon lifts had to be castRout of plumb9 !ith the embedded cable anchors still set to tight

angular tolerances.

The +ooper /iver Bridge in +harleston" South +arolina !as (at the

time) the longest cable staed bridge in *orth merica. The

slenderness of the plon legs and the lack of a cross beam belo! the

cable anchorages made plon leg construction a challenge. The

selection of %,/& self-climbing form!ork made it impossible to place an instrument bracket on the form!ork support frame" so !e


31/41

emploed a Trimble 61%S solution. ,arl in the morning"

immediatel after a section of the plon leg !as cast" !ith the

concrete in place for :-> hours" !e installed a special instrument

pedestal onto a Rcast in9 pipe flange. The to!er crane picked up a 24ton test block (to make the mast load neutral) and then s!ung to a

position that permitted the 1%S receiver to receive the maimum

number of Rclean9 satellite signals. We used a set of three Rone

minute9 static position averages" capturing one position ever

second" to determine our @ position and an approimate H. We

corrected the !eaker H position b taping a Uelevation up from the

previous lift. We then replaced the 1%S antenna !ith a Leica total

station and obtained an angular orientation from a back sight" setabout 3 km a!a. We set t!o auiliar instrument brackets on the

inside face of the eposed cable anchor bo" and then surveed their

positions for use in a =6imensional RBest $it9 solution.

The actual as-built of the most recentl cast lift took place =-: hours

later" long after sunup and !ith the to!er crane in full operation" but

!e could use a least s'uares solution to correct for temperature

gradients and eccentric load induced to!er deflections b turning off the internal compensators" observing the auiliar bracket positions

again" then taking measurements to our concrete lift as-built

positions last. 6uring post processing" !e applied a E parameter

similarit transformation to the observed data to perform the scale

factor" rotations and transformations necessar to get the instrument

position and the auiliar bracket positions to match the 5>755 M

positions" before sunup and !ith the to!er crane neutral. These

transformation parameters !ere of course applied to the as-builtmeasurements" to convert them to 5>755 M readings.

The Shaikh Haed Bridge !as not a cable staed bridge" but rather a

cast in place concrete deck supported b cable stas from a series of

asmmetrical steel arches. This pro#ect !as designed b Haha adid"

engineered b %/ and proved to be almost unbuildable and

absolutel unprofitable for the main contractor. &t is currentl 3 ears

behind schedule" !ith about 2? months to go until completion. &

staed on this pro#ect onl until & found an eit strateg J the Sutong


32/41

Bridge" in *antong %/+.

The Sutong Bridge is currentl the !orld9s longest cable staed

bridge" !ith a clear span length of 25?? metresV B comparison" theBandra Worli9s main span is 455 metres. Cltra-long span bridges

bring a mriad of technical challenges" !hich directl impact the

pro#ect costs and construction schedule. Long decks re'uire tall

to!ers (to be able to accommodate the increased number of sta

anchors" and still maintain the necessar angular cable geometr).

Sutong9s plons !ere =5> Metres in height" as compared to Bandra

Worli9s tallest plon at %2G" at 23: Metres. The crossing of the

@angtAe /iver" bet!een *antong and SuAhou has strong !indsduring most of the ear so deck flutter and to!er deflection !ere

much more of a problem than thermal gradient induced deflections.

The plons !ere so tall" that after 355 metres" t!o auiliar

instrument positions had to be transferred onto the plon" to perform

set out and as-built surves" similar to the +ooper /iver Bridge"

ho!ever the +hinese chose a more traditional approach J a

reciprocal observation procedure !ith a Leica 355= total station. The

rebar for the lifts above !ere much too tall to permit a 1%S antennato receive satellite data free from multi-path errors.

The anchor boes for the plons !ere fabricated close to Bei#ing"

and then barged do!n to *antong. These boes !ere 'uite similar to

the Bandra Worli boes" and the surve control methodolog chosen

!as mine" a combination of metrolog and steel fabrication

Rdimensional9 'ualit control. The onl serious challenge in anchor

fabrication is to achieve angular accurac in the three planes (" Xand g)" $T,/ the !elding is completed. nticipating angular

errors due to !eld shrinkage" and mitigating unepected results is

almost an art J not a science. &f the acceptance criteria for angular

errors is K- 5.4 degrees (fabrication and installation errors combined)

that means that the post !eld fabrication error must be bet!een K-

5.34 degrees and the pre-!eld fit-up errors bet!een K- 5.234

degrees. &n an anchor plate of :55:55mm" that means making

repeatable surve measurements of sub-millimetre accurac. Thislevel of accurac demands the best 2st order instrumentation" on-


33/41

board soft!are" customiAed targeting and methodolog available.

Both the *antong and the Bandra Worli anchor boes !ere

manufactured and installed !ithin the designer9s tolerances.

& also consulted to a bridge pro#ect in +anada" a long floating bridge

in the province of British +olumbia. The challenge the faced that

prompted m involvement !as completing the plon leg

construction once the pontoons !ere afloat. gain" & designed a

sstem based on a E parameter similarit transformation" utiliAing a

total station that could operate !ith the internal compensators

deactivated" and a series of control points originall established

!hen the pontoon !as still in the dr dock.

91 Could you please tell us briefly ho! a cable stayed bridge is

different from other bridges2 +able sta supported bridges are a

tpe of suspension bridge. tpical suspension bridge" like the

1olden 1ate Bridge in San $rancisco" consists of t!o large diameter

incrementall spun cables" hanging bet!een the t!o main to!ers" on

a catenar" !ith much smaller diameter vertical hangers spacedevenl along the deck" connected to the suspension cables.

+able staed bridges have man smaller diameter cables" connecting

the plon legs to the deck at evenl spaced intervals. The pattern of

plon connection can var. The parallel sta sstem is called a

Rharp9" the sstem that bunches the plon anchors close to the top of

the plon is called a Rfan9" but the most common stle is to space the

anchors from the plon top do!n!ards to!ards the deck. Thissstem is called a modified fan.

The longest spans still re'uire a suspension bridge" but for the

medium spans (255 J 2555 metres)" cable staed bridges ma offer

cost benefits and shorter construction schedules to the client.

The suspension bridge needs large" epensive abutments to Ranchor9

the suspension cables" and the time it takes to spin the suspension

cables is length. &f the span distance permits" a cable staed bridge


34/41

alternative offers about 23 months gain in the schedule" as no

spinning delas are re'uired. possible compromise is a hbrid

design" !here a portion of the bridge deck is partiall suspended b

cable stas" !hile the suspension cable is being spun" and then uponcable spinning completion" the mid span portion of the deck is

suspended b hangers from the catenar cables. The cost benefit is

slight !ith this alternative" so is rarel chosen. Multiple span cable

staed bridges are also a cheaper alternative for long span bridge

designers" such as the /ion ntirrion Bridge in 1reece. The minor

dra!back to this solution is that the navigational channel is cut into

smaller portions b the etra plons.

:1 Please tell us about some of the sur,ey related challenges you

faced on the Bandra (orli Sea $in& Bridge2 The surve related

challenges for the Bandra Worli !ere similar to most cable staed

bridges. The accurac re'uirements are al!as demanding"

especiall in the fabrication of the cable anchor assemblies. The

angular misalignment permitted isK- 5.4 degrees in the completedstructure" so the fabrication and assembl tolerances are much

tighter. We fabricated the bearing plate D guide pipe assemblies to K-

5.5> degrees from perpendicular. We placed them in the deck slab

form!ork (prior to concrete placement) !ithin K- 5.234 degrees" to

ensure that the !ould still be !ithin K- 5.34 degrees after the

concrete had been placed and the concrete curing shrinkage !as

complete. This procedure re'uired custom design D manufacture of

ver accurate bearing plateDpipe sleeve assembl #igs" as !ell as

special dual turnbuckle pipe sleeve support okes and customiAed

targeting and tooling for surveing the anchor assemblies in the deck

sections.

The fabrication of the plon head anchor boes !as even more

comple" as !eld shrinkage had to be anticipated" and unforeseen

results dealt !ith during erection. The siAe of the base plate that the

bearing plate rests on is onl E55Y:55 mm in dimension" so that

means the fit-up surve measurements had to be accurate to sub-


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millimetre" to ensure the 5.234 degree angular misalignment

specification !as met.

The plon legs (belo! the to!er head) !ere ver slender" so !eresusceptible to thermal gradient deflections. +are had to be taken to

ensure that all important surves !ere performed in a thermall

neutral state. The legs also deflected to!ards the plon centre after

concrete placement" so the Ras-set9 positions !ere al!as different

from the Ras-built9 positions.

The reference geometr supplied b the designer is based on Time

Z" !hereas !e !ere constructing ever element at Time 5" soallo!ances had to be made for future creep" shrinkage and elastic

shortening. These allo!ances are referred to as pre-cambers and

over heightsDlengths. $or eample" the over height for the %2G

plon9s to!er head !as K=4 mm. s !e completed the south

carriage!a first" the deck load !as transferred into the plon legs"

causing the shared centre legs to shorten less than the single outer

leg. This caused the plon to temporaril incline a!a from bridge

centreline b nearl =5 mm at the top of the to!er head. This meantthat !e had to construct the north plon9s to!er head on a similar

inclination" !ith the epectation that the plon !ould come back to

plumb !hen the load of the north deck !as in place" bringing the

plon sub structure and common foundation back into e'uilibrium.

;1 Could you please elaborate on the role of the pylons in a cable

stayed bridge and the sur,ey methodology that !as used to put

them up in the Bandra (orli Sea $in& Bridge2 The plons of a

cable staed bridge are used primaril to anchor the upper cable stasockets. Man times the deck is firml attached to the plons (as in

the case of the Bandra and Worli spans) but other bridges onl have

sliding pot bearings at the plons (Ting 0au Bridge" in ong 0ong)"

or elastomeric bearings bet!een the to!er9s cross beam and the

underside of the deck (le $raser Bridge" +ooper /iver Bridge).

The plon must be tall enough to provide sufficient space for all the

cable anchors" and still ield a decent vertical angle at the uppermostcables. bviousl" as the alpha angle decreases !ith the height of the


36/41

anchor above the deck" the amount of cable force in the vertical

direction decreases as the force in the horiAontal direction increases.

This is !h the diameter of the longest cables is greater than those

nearest the plon (!ith the steepest alpha angles). The have to bestrong enough to resist the etra cable force applied" to ield

sufficient up!ard lift to support the dead load and the live load

(traffic) in the !orst case scenario.

The surve method utiliAed to construct the Bandra Worli plons

!as based on the fact that the plon legs !ere inclined. &nclined

plon legs pose a significant challenge to the contractor" as the rebar

cage !ill have a natural tendenc to sag do!nhill duringconstruction. &f a rebar cage sags" it !ill be out of tolerance !hen

completed and clash !ith the form!ork ad#ustment procedure during

the final as-set surve. ur solution !as to implement a sacrificial

rebar template assembl" to guide the construction of the rebar cages

and to ensure that there !ould be no clashes of the steel embedment"

like crane tie-ins and 60 climbing cones.

ur surveors set the rebar templates in the earl morning hours"after the self-climbing form!ork !as fied for the net lift. These

templates had = or : ke points stamped onto them that the

surveors could shoot" and once the support frame!ork !as

completel interconnected" formed a local surve net!ork that

moved !ith the plon9s thermal deflections" et !as still based on a

thermall neutral plon. t an time" and !ith an amount of plon

leg deflections present" our surveors could set up their instrument

on the special brackets attached to the 60 frame!ork" disable

the internal compensators and then perform a Rresection9 or Rfree

station9 operation to determine instrument co-ordinates and

orientation" for set-out !ork. nce the concrete !as placed" the

plon !ould deflect do!n!ards to!ards the bridge centreline" so

ne! co-ordinates of the rebar template !ere measured (again in the

earl hours of the morning). The instrument !as again transferred up

to the top of the plon" installed on the same bracket" !here the as-

built surve could be completed 'uickl and accuratel.


37/41

The main challenge to these surves !as in the form!ork

construction. n most bridge plons" there are 3 fied panels and

t!o ad#ustable panels" so fine ad#ustment at each corner is possible.

$or the Bandra Worli plons" the form!ork had no ad#ustabilit.,ach panel butted up to the ad#acent panels" so the entire shutter

assembl acted as a solid bod. To move the top into position" the

entire shutter had to be tipped" similar to the surve alignment

procedure of an elevator core shutter. &f an error in a panel length

cutting operation occurred" there !as no !a to eliminate this. Small

errors could be mitigated b setting the shutters so that half the error

!as on one corner and the other have !as on the opposite corner.

ur surve alignment criteria !as therefore based on the centroid ofthe entire shutter (> point average in the plon leg sections Q 23

point average in the to!er head sections)" and not on individual

corner positions.


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G. 6eck profile surves

25. Wet #oint alignment bet!een 2> deck segment Rblocks9

22. 6eck closure surves" pre cable length fine tuning

23. %ost fine tuning deck profile surves

2=. 0erb and asphalt grades

=1 (hat &inds of sur,ey instruments are best suited for thedifferent sur,ey !or&s in a typical cable stayed bridge

construction1 The best instruments for cable staed bridge

surveing are state of the art" high accurac" vibration tolerant

electronic total stations" !ith T/ (automatic target recognition) and

on-board soft!are for $ree Station and /esection.

1%S receivers can also pla a role" !hen the plons are etremel

tall (as in the Millau Bridge in $rance) or far out to sea. Their lack of accurac in H measurements is their onl !eakness" in m opinion.

With improvements in multi-path error mitigation and the

implementation of the 1lonass satellites" the availabilit issue and

%6% are much improved.

The eception to this high tech e'uipment is utiliAing a pair of old

fashioned tilting levels to perform accurate deck profiles. The

vibrations present in cable sta supported decks makes internallcompensated surve e'uipment susceptible to Rcompensator

ecitation9" producing a blurred image of the crosshairs in an auto

level or randoml inaccurate vertical differences in total stations.

split bubble tilting level ehibits the deck vibrations in the

movement of the tilting bubble J !hile the cross hair image remains

completel stable. B ad#usting the level so as to balance the bubble

movement evenl" a level observation is possible. The purpose of

having t!o instruments observing a single staff is that long circuits

can be run Rone !a9. ,ach set-up produces t!o back sights and t!o


39/41

foresights" so constitutes a closed level loop. The net set-up again

produces 3 back sights and t!o foresights" !hich is again a closed

loop. &t is like building a chain" link b link. &t !as 'uite common to

be able to level from %2E to %32" a distance of >55 Metres" !ith amisclosure of onl 2-3 mm.

>1 Could you tell us about the &ind of accuracies that are needed

for ,arious aspects of a cable stayed bridge2 There are man

different accurac re'uirements" in the steel fabricationDconcrete

casting and their related surve control measurements" as some tpes

of errors can propagate or sstematicall multipl and others are

essentiall Rone off9 J !ith no knock-on effects.

6eck segment lengths are a tpical dimensional component that has

potential for sstematic error propagation. K2mm error on ever

=M long deck segment of a >55 metre span !ill produce K255 mm

errors at each epansion #oint at the end spans" or roughl 25 of

the thermal gradient epansion range. This is still an acceptable

range of error" but 355 or =55 mm !ouldn9t be" so deck lengths have

to be measured accurate to the millimetre" and significant errorsmust be tracked during deck segment installation" and compensated

for in the last in situ stitch #oints cast.

&nstallation of the first deck segment of a 2> segment block is

another eample of a potential sstematic error situation. $or ever

2mm rotational error (in either the horiAontal or vertical directions)

there !ill be a 2>mm error at the net !et #oint. When setting these

segments during !et #oint construction" !e measure the horiAontal

positions to the millimetre and the vertical differences to better than5.4 mm.

+able anchorage placement errors in either the deck or plon are

minor" as there is usuall a fairl generous range of cable length

ad#ustment at the live end socket J either b split shims or b

threaded sockets and lock nuts. shift of 2 or 3 centimetres in

longitudinal or transverse directions is insignificant" so normal

surve procedures are 'uite capable of controlling installation andidentifing absolute errors. The eception to this is angular


40/41

misalignments. The principal of multi-strand stas" or parallel !ire

pre-formed stas is that each !ire or strand carries an e'ual

proportion of the cable force. &f the bearing plate isn9t perpendicular

to the cable force vector" then some !ires !ill carr much more oftheir respective share of the force" and other !ires !ill carr much

less of the force. The over-stressed !ires are therefore susceptible to

premature fatigue failures. Most manufactures !ill provide a

!arrant period for their stas" providing the final angular

alignments are !ithin K-5.52 /adians (K- 5.4E degrees). ,ven !ith

this Rless than generous9 installation tolerance" longer guide pipes

!ith a misalignment close to the limit !ill pose problems during

damper installation. This is the one phase of !orks that re'uires the best surve e'uipment and methodolog available" to produce

repeatable measurements at sub millimetre accurac.

The actual positions of the anchors need to be measured accuratel"

onl &$ the cables are to be installed to length" instead of force. s

absolute cable lengths at the installation forces are ver difficult to

determine" engineers rarel use length as an installation criteria" and

instead choose force (as measured at the hdraulic #ack pump). slong as the cable anchor socket has sufficient capacit for minor

length errors" the cable length" deck anchor and plon anchor

locations need onl to be !ithin 3 cm of design.

%ile driving and coffer dam positioning can be performed to K- 4mm

!ithout an detrimental effects" so is a perfect application for 61%S.

:: ?1 Ho! important is the use of 0PS for sur,ey purposes in a

cable stayed bridge pro+ect2 Ho! !as it used in the Bandra

(orli Sea $in& Bridge pro+ect2 The application of 1%S in cable

staed bridge construction is 'uickl gaining acceptance" for specific

tasks. While it can9t replace all traditional surve e'uipment J it

does have cost benefits in certain applications.

Bridges far from shore" ver tall plons" marine plant positioning" bathmetric vessel positioning" and construction site control


41/41

net!orks are all perfect applications for 61%S. @ou can even use

static 1%S receivers for as-builts" provided the H co-ordinates are

not critical.

&n dnamic structures that re'uire periodic monitoring" a 61%S

sstem that logs reading once per second" over 3: hours is a much

more cost effective solution than a t!o man cre! !ith a total station

and prism pole.

s the Bandra Worli Bridge is fairl close to shore" 1%S plaed a

limited role in construction control.

Documents

Making of Bandra Bridge