08 - structures

GautrainPreliminaryDesignReportPhase1 81

8. STRUCTURES

*NOTE: SOME OF THE INFORMATION IN THIS CHAPTER ISAPPLICABLE TO PHASE 2 PRELIMINARY DESIGN. THISINFORMATION MIGHT CHANGE IN THE PHASE 2 PRELIMINARYDESIGNREPORT.

8.1 INTRODUCTION

Structureshavebeenredesignedtoconformwithminorrevisionstovertical alignment and to match the reduced Electrostar gauge which isalsosuitableforanumberofothertraintypesresultingin:

Reducedconstructioncosts

Reducedconstructiondurationsandprogrammerisk.

More efficient foundation designs have been incorporated, with arisk sharing/remeasurable mechanism for pile lengths exceedingthe baseline design proposed (in the dolomite areas aroundCenturion).

Lateralsupportandcutandcoverdesignsandmethodshavebeenrevised,resultingin:


Reducedconstructiondurationsandprogrammerisk.

GeneralarrangementofRosebankandSandtoncutandcovershasbeencompletelyrevised:

AtRosebanktheoverallareaof thecutandcoverhasbeenreducedby66%

AtSandtonStation,a revisit of the switch trackanda slightlengtheningofthecutandcovertowardsthenorth(uptojustsouthofDonSuiteHotel)hasenabledthestationtoberaisedby 7 m (ie platform level at 33 m depth in the axis of thestation).Simultaneously,onsouthernend,asaconsequenceof this raise, the huge and costly undergroundwork for thebackstation (complicated and wide track layout) has beenreplaced by a 120m lengthening of the cut and cover, thewholebalanceoftheconstructioncostandprogrammebeing


fullypositive(refertodrawing4028).

Viaduct construction method has been changed to precastsegmentalconstruction,offeringthebenefitsof:


Reducedconstructiondurationsandprogrammerisk

Improvedqualityoffinish

industrializationof theproduction, thereforeenhancement ofBEEinvolvement

(a) Overpassandunderpassbridges

Thefollowingscheduleillustratestheconfigurationofoverpassandunderpassbridgestructures

OVERPASSES&UNDERPASSES

NO. NAME KMAXIS

Overpasses

N/A

N/A

OvP3 N3offramp 16920

OvP4 N3freeway 17025

OvP5 N3onramp 17135

OvP6 Marlborodrive 17315

OvP7 ThirdRoad 17500

OvP8 Firstavenue 17825

OvP9 Ridgeroad 24715

OvP10 Westroad 25580

OvP11 Dalestreet 27000

OvP12 Newroad 29068

OvP13 K56 29503

OvP14 Douglas 30214

OvP15 K27/K562 33504

OvP16 Brakfontein 37505

OvP17 Freight 37729

OvP18 N1Offramp 38007

OvP19 K54Nelmaplus 39599

SouthNorth

OvP20 K109Future 42015


OvP21 JohnVorster 43718

N/A

OvP22 VonWillich 46168

OvP23 RabbieStreet 46526

OvP24 K103 48928

OvP25 Access to 4VRP(b)

51434

OvP26 Bourke(a) 57895

N/A

N/A

OvP33 Burnett(a) 60595

OvP34 Festival 60980

OvP35 Hilda 61235

OvP36 Grosvenor 61490

OVERPASSES&UNDERPASSES

NO. NAME KMAXIS

Overpasses

OvP101 N3offramp 1506

OvP102 N3freeway 1595

OvP103 N3onramp 1689

OvP104 Starfieldavenue 1920

OvP105 Thirdroad 1988

OvP106 Firstroad 2769

OvP107 Lovatoroad 9793

WestEast

OvP108 Chestnutstreet 11980

Underpasses

UnP1 ZinniaDrive 15935

UnP2 KingWillow 32912

UnP3 ROW 34808

UnP4 Sanrand 35030

UnP5 Olievenoutbosch 35567

UnP6 K220 36725

UnP9 Snakevalley 50296

UnP10 R28Ramps 50446

UnP15 Vanderwalt 56580

UnP20 Walker 59000

SouthNorth

UnP21 Walkerspruit 59185


UnP22 WaltonJameson 59235

UnP23 Lynnwood 59860

UnP100a Zinniadrive 490

UnP100b Zinniadrive 443

N/A

UnP102 Centenaryway(b) 6314

UnP103 Centenaryway(b) 6322

UnP104a Modderfonteinroad 8574

WestEast

UnP104b Modderfonteintroad 8574

TOTAL 55No

(b) Viaductstructures

Thefollowingscheduleillustratestheconfigurationofviaductstructures

VIADUCTS

NAME LENGTH

01N/Slanes 352.00

11AW/E1lane 176.00

11BE/W1lane 220.00

11CE/W2lanes 264.00

VIADUCT03 616.00

VIADUCT04 748.00

VIADUCT05 264.00

VIADUCT06 484.00

SouthNorth

VIADUCT07 113.00

VIADUCT12 264.00

VIADUCT13 484.00

WestEast

VIADUCT14 616.00

TOTAL 4601m


(c) Cutandcoverstructures

The following schedule illustrates the configuration differences between cut andcoverstructures

CUTANDCOVERSTRUCUTRES

NAME LENGTH

CC0 ParkStation 252.00

CC1 RosebankStation 669.00

CC1bis SandtonStation 668.00

CC2 Marlboro 123.00

CC2bis Flyover 128.00

CC3 JohnVorster 1170.00

CC3bis Centurion 1480.00

N/A

CC5 JeanAvenue 680.00

CC6 BeforeSalvakop 750.00

CC6bis PretoriaStation 505.00

CC7 PretoriaCentre 585.00

SouthNorth

CC8 Muckleneuk 235.00

CC11 RhodesfieldStation 370.00WestEast CC12 JIAStation 95.00

TOTAL 7710m

8.2 DESIGNOFSTRUCTURESSUMMARY

8.2.1 Introduction

This document gives a summary of structures along the proposedalignmentoftheGautrainaswellastherelevantdesigncriteria.

Thedocumentisstructuredinthefollowingway:

Generaldescriptionofstructures

DesignCriteria

Viaducts.


OverandUnderpasses.

CutandCovers.

8.2.2 Generaldescriptionofstructures

A schematic view of all the structures can be seen on the drawingnumberBOMBYVIDWG4100"GeneralSchematicofStructures".

Some exceptions are noticeable, made mainly in the view of betterbalance the earthworks as well as to reduce the total length of theviaducts:

atModderfonteinSpruit(km21,2):dropoftheprofileforearthworkbalance purpose, and replacement of the viaduct by anembankmentplusaculvert

reinstatementofDouglasRoad(km30,2) insteadofGeorgeRoadforearthworkbalancepurpose

at CentenaryWay (EW km 6,33): drop of the profile in order toshorten the viaduct and better integrate the Gautrain within theLimbroPark

8.2.3 Viaducts

(a) General

A typical 44,0m simple span prestressed concrete deck structure isconsidered.Prestressingisbothexternalandinternal(splitapproximatelyequally).Thechoiceofsimplespansisrelatedtotherequiredlimitationofmovements between track and deck for railway structures. Thefoundationsofeachpieraredesignedtoresist totraction/brakingforcespersimplespan.

Thedeckstructureisaconcreteboxgirderoftypically10,10mwidth(2tracks3,5mwidth,Electrostargauge)andconstantheightof3,5m.

Thechoiceof44,0mspansisacompromisebetween:

wider spanned structures which limit the number, locationproblems and costs of piers and foundations, but requiresignificantmeasuresintermsoferectionmethods,and

short spans structures (typically 30,0m) with concrete beamsdeck,whicharegloballymore simple to fabricateanderect, but


multiplytheproblemsofpierlocations(quitelargeincertainareasof the scheme, considering the dense road layout) and offer arather worse integration and appearance on an environmentalpointofview.

The chosen design remains compatible with a good standardisation ofthefabricationanderection.

There is no need of special trackdilatation devices for viaducts of thistypeofconstruction,whereasviaductsconceivedasmultiplespanswitha total lengthgreater than400m to500mwouldhave requiredspecialrigidspansandtrackdilatationdevices.

Wesummarizehereaftertypicaldimensionsofthestructure:

Deck: 44,0msimplespans

meanthickness

(concretem/m) 0,59m(2tracks),

0,75m(1track)

reinforcement ratio 170kg/mprestressing60kg/m.

Piercaps: 4,0mx3,0m

thickness1,50m

reinforcementratio150kg/m.

Piles: 4,0mx3,0m,

thickness0,40m

crosssectionalarea=4,41m

reinforcementratio:90kg/m.

Pilecaps: reinforcementratio90kg/m:

Typesanddimensionsoffoundationsdependingonsoilconditionsandpierheightreferto8.1.3(b)

(b) Foundations

The following assumptions have been made for the design offoundations:

Viaducts05HennopsRiverand06EeufeesRiver(dolomiticzone),aswell as viaducts 12Modderdonteinand14 (ZuurfonteinRoad)onpiles:


Max.pierheight=13m:

Pilecaps5,70mx7,20mx1,50m.

Piles:4pilesof1,20mdiameterperpier

13m


bridges (35out of a total of 55), requiring thehighest possible levelofindustrialisationandstandardisation.

Reinforced concrete frames areprovided in specific cases (total of 20)becauseoflittleskewangles,lesscompatiblewithbeamdeckbridges.

Besidesthefactthatbridgestructuressupportingtrain loadshavetobedesignedforhigherloads,thechosenstructuretypesdependessentiallyonnecessarygaugesandskewangles.Wegivehereafterasummaryofthe different types of overand underpasses we adopted for thedeterminationofthenecessaryquantities.

Complete schedules of overpasses (Annexure 8D) and underpasses(Annexure8E)aregivenintheannexuresafterthissection.

8.2.5 CutandCovers

Wehaveconsideredtwotypesofstructures,dependingonthepossibleconstructionmethodology:

Whentherearenoconstraintstoostringentintermsofland,usualconcreteboxesarecastinplaceinopencut,eithersloped(withsoilnailingandgunitewhererequired),orverticalwithtemporarypiling.

OVERPASSES

TYPEdeck

concretem3/m

deck:ratioprestressing

kg/m3

deck:ratioreinforcement

kg/m3

supports:ratioreinforcement

kg/m3

1 3spans,mainspan15mprecast

prestressed0.5 42 80 80

2 4spans,twomainspans15mprecast


34spans,twomainspans15mand22.30m

precastprestressed

0.5 42 80 80

4 concreteframereinforcedconcrete

2,5*)inclsupports

100 100

UNDERPASSES

TYPEdeck

concretem3/m

deck:ratioprestressing

kg/m3

deck:ratioreinforcement

kg/m3

supports:ratioreinforcement

kg/m3

4A concreteframereinforcedconcrete

2.5*)inclsupports

100 100

4Bconcreteframewithcentralsupport

reinforcedconcrete

3.0*)inclsupports

100 100

6 3spans,centralspan20mprecast


7 4spans,twocentralspans20mprecast


CHARACTERISTICS

CHARACTERISTICS


In very constrained urban context, and in deep conditions, thedesignenableslateralsupportsolutionstobeincorporatedintothepermanentstructure,inorderto:

reducetheconstructioncosts

improve the construction efficiencies and ease theprogrammedurations

minimizethestructuralfootprintsinurbanareas

toimprovetheaccomodationoftraffic

For the1st case (concreteboxescast insitu inopencuts), three tyoicalcrosssectionshavebeenconsidered:

2 twinboxes (onebox forone track, 4.72m internalwidth) partiallyinCC2bisandCC11

1 boxwith centralwall (for 2 tracks, 9.74m internalwidth) ,which is the general case, the central wall acting asintermediatesupport (optimisationof theconcretestructure),and improving simultaneously the safety in separating the2tracks

1boxwithoutcentralwall(for2tracks,8.84minternalwidth).partiallyonCC6bisandCC7

Thicknessofwalls,slabandroofsaredirectlyfunctionoffillheightabovethecutandcoverstructure.Wegivehereafterasummaryofthisforthe3differenttypesofcutandcovers:

Thicknessofwalls,slabandroof

2twinboxes Box withcentralwall

Box withoutcentralwall

Heightoffill


In the second case (lateral supports are incorporated into permanentstructures):

the lateral supports, temporarily anchored, are constructed,dependingonthegeologicalconditions,eitherwithdiaphragmwalls(CC0&CC12)orwithpileswalls (typicallyat2,5mspacing)withguniteinbetween(CC1,CC1bis,CC2,CC3,CC7)

thetopandintermediateslabsareconstructedwithprecastgirdersand200mmslab

The others structures take into account specific design constraints(launchingshaftforTBM,3trackssectionsetc).

8.2.6 Annexures:StructuresSummaries

Annexure8A: ViaductsSummary

Annexure8B: CutandCoversSummary

Annexure8C: TypicalBridgeTypes

Annexure8D: Overpasses

Annexure8E: Underpasses

8.3 STRUCTURESDRAWINGS

SeeVolume2ofPhase1.


ANNEXURE8C:TYPICALBRIDGETYPES

Overpassesandunderpasses:Precastbeamsolution

Structuraltype

Thestructuraltypesproposedareclassifiedasfollows

Type1 Overpassstructurewith800mmdeepbeamsand200mminsitutopslab.Deckwidthstosuittheroadscrossingover.Spanstosuitthedepthoftrackbelowroadlevel.

Type2 Overpassstructurewith800mmdeepbeamsand200mminsitutopslab.Deckwidthstosuittheroadscrossingover.Spanstosuitthedepthoftrackbelowroadlevel.

Type6 Underpassstructurewith1000mmdeepbeamsand200mminsitutopslab.Deckwidthstosuitthetracksover.Spanstosuittheroadwidthsanddepthofroadbelowtracklevel.


Type7 Underpassstructurewith1000mmdeepbeamsand200mminsitutopslab.Deckwidthstosuitthetracksover.Spanstosuittheroadwidthsanddepthofroadbelowtracklevel.

Overpassesandunderpasses:Framesolution

Structuraltype.

Thestructuraltypescanbeclassifiedasfollows.

Type4 Overpasseswithdeckwidthstosuittheroadscrossingover.Spantosuitthewidthoftrackformation.

Type4a Underpasseswithdeckwidthtosuitthetrackcrossingover.Spantosuittheroadwidthunder.

08 - structures

Documents

na unp102 c

preliminary design

4vrpb51434ovp26 bourkea

thebackstation complicated

reduced electrostar

costly undergroundwork

wide track layout

chapter isapplicable