Table Of Content.
August2002 SUBSTRUCTURESANDBEARINGS 19(0
TableofContents
Section Page
19.1 ABUTMENTS 19.1(1)
19.1.1 General 19.1
19.1.2 Loads 19.1
19.1.3 GeneralDesignandDetailingCriteria 19.1
19.1.4 Semi-IntegralAbutments 19.1
19.1.5 IntegralAbutments 19.1
19.1.5.1 General 19.1
19.1.5.2 DesignCriteria 19.1
19.1.5.3 SuperstructureandInteriorSubstructureDesignCriteria 19.1
19.1.5.4 IntegralAbutmentDetails 19.1
19.1.6 Free-StandingAbutments 19.1
19.1.6.1 Usage 19.1
19.1.6.2 Epoxy-CoatedSteel 19.1
19.1.6.3 SeismicShearBlocks 19.1
19.1.7 PileSpacingsandLoads 19.1
19.1.7.1 GeneralDesignCriteria 19.1
19.1.7.2 PileDesignforIntegral/Semi-IntegralAbutments 19.1
19.1.7.3 PileDesignforFree-StandingAbutments 19.1
19.1.8 Wingwalls 19.1
19.1.9 Drainage 19.1
19.1.10 Joints 19.1
19.1.10.1 ConstructionJoints 19.1
19.1.11 Concrete 19.1
19.2 INTERMEDIATESUPPORTS 19.2
19.2.1 Types. 19.2
19.2.1.1 PipePileBents 19.2
19.2.1.2 Piers 19.2
19.2.1.3 Multi-ColumnBents 19.2
19.2.1.4 Single-ColumnPiers 19.2
19.2.2 GeneralDesignConsiderations 19.2
19.2.3 SpecialDesignCriteria 19.2
19.2.3.1 PipePileBents 19.2
19.2.3.2 HammerheadPiers 19.2
19.2.4 PierandBentinaSlopedEmbankment 19.2
19.2.5 DynamicLoadAllowance(IM)forPiersandBents 19.2
19(ii) SUBSTRUCTURESANDBEARINGS August2002
TableofContents
(Continued)
Section Page
19.3 BEARINGS 19.3(1)
19.3.1 General 19.3(1)
19.3.2 FixedSteelBearings 19.3(3)
19.3.2.1 General 19.3(3)
19.3.2.2 Design 19.3(3)
19.3.3 SteelReinforcedElastomericBearings 19.3(5)
19.3.3.1 Elastomer 19.3(5)
19.3.3.2 BehaviorofSteel-ReinforcedElastomericBearingPads.. 19.3(6)
19.3.4 DesignofSteel-ReinforcedElastomericBearingPads 19.3(8)
19.3.5 SeismicDesign 19.3(8)
19.3.5.1 Application 19.3(9)
19.3.5.2 SeismicPerformanceZone1Criteria 19.3(9)
19.3.5.3 ConnectionsforFixedSteelShoes 19.3(10)
19.3.5.4 ConnectionsforElastomericBearingsandPTFE/
ElastomericBearings 19.3(10)
19.3.5.5 SeismicIsolationBearings 19.3(11) #
•
August2002 SUBSTRUCTURESANDBEARINGS 19.1(1)
ChapterNineteen
SUBSTRUCTURESANDBEARINGS
Section 11 of the LRFD Bridge Design 2. Integral Abutment. Flexible abutment
Specifications discusses the design withoutajointbetweenthebackwall and
requirements of abutments, piers and walls. pilecap(incrosssection,thebackwalland
ChapterNineteenpresentsMDTsupplementary pilecapmay,infact,appearasamonolithic
information on the design ofthese structural rectanglewithnoapparentcap).
components. Section 13.4 of the MDT
Structures Manual presents Department 3. Free-standing Abutment. Rigid abutment
criteria for the selection of substructure withajointbetweenthebridgedeckandthe
componentswithinthecontextofstructuretype backwall.
selection.
Figure 19.1Apresentsschematicsforthethree
basic types ofabutments. Each ofthese is
19.1 ABUTMENTS discussedinthisSection.
19.1.1 General Abutments shall generally be ofthe cast-in-
place,reinforcedconcretetype. Theyshallbe
Anabutmentcanincludeabackwall,acapand founded on spread footings, drilled shafts or
wingwalls. Theterm"endbent"isoftenused drivenpilefootings.
interchangeablywith"abutment."Abackwallis
theportionoftheabutmentwhichfunctionsasa Ajointlessflexibleabutment,eitherintegralor
wallprovidinglateralsupportforfillmaterialon semi-integral, ispreferred. Free-standing rigid
whichtheroadwayrestsimmediatelyadjacentto abutments shallbeusedwheretheanticipated
thebridge. translational movements ofthe piles are too
great, or settlement of the backwall is
Abutmentscanbeclassifiedasrigidorflexible anticipated. The force effects of these
abutments. Flexibleabutmentseliminatejoints displacementsmustbeincludedinthedesign.
attheendofthesuperstructurebyintegrating
the bridge deck with the backwall. Rigid
abutments incorporate expansionjoints atthe 19.1.2 Loads
end ofthe bridge between the deck and the
backwalltoaccommodatethermalmovements. Reference: LRFD Articles 11.6.1.1 and
Flexible abutments must be able to 11.6.1.3
accommodate the movements through elastic
behaviorofthebridgeandthesurroundingsoil Thestaticearthpressureshallbedeterminedin
becausethedeckisintegralwiththeabutment. accordance with Article 3.11 of the LRFD
Specifications. Generally, no passive earth
An abutmentmaybe designedas one ofthe pressureshallbeassumedtobegeneratedbythe
following three types in descending order of prismofearthatthenearfaceofthewall.
preference:
1. Semi-integralAbutment. Flexibleabutment 19.1.3 GeneralDesignandDetailingCriteria
withapinjointbetweenthebackwalland
captofacilitateconstructionandsubsequent Thefollowingappliestothedesignanddetailing
maintenance. ofbackwallsandwingwalls:
19.1(2) SUBSTRUCTURESANDBEARINGS August2002
#
Semi-IntegralAbutment
Cwaotnetrinusotuospneoprene
IntegralAbutment
'.'V
#
;.1i-.-1:••)t•
+-M
FreeStandingAbutment
'••'••;':i*;
T...'i-x.^^1
TYPICALABUTMENTTYPES
(il)
Figure19.1A
August2002 SUBSTRUCTURESANDBEARINGS 19.1(3)
1. BridgeApproach.TypicalMDTpracticeis 6. Backwall/Wingwall. Thejunction ofthe
to design for the future possibility ofa abutmentandwingwallisacriticaldesign
bridge approach slabbutto notbuildthe element,requiringspecialconsiderations. If
slab in the initial construction. When thewingwallistiedtothebackwall (i.e.,
reinforced concrete bridge approach slabs thereisnojoint),designforat-restpressure.
are used, live load surcharge will notbe All reinforcementmustbe developedinto
considered on the endbent; however, the both elements such that full moment
vehicularloadsontheappropriateslabsshall resistancecanbeobtained.
beconsidered. Anchortheappropriateslab
tAotrhiegiadbuatpmpernotaschifisnlaabhhieglhpsseitsomipcrezvoenen.t 7. pBraecfkewrarledl(Bia.et.t,ern.o bVaetrtetri)c.al Fboarckwtaalll,lsfraere-e
compaction of the backfill behind the standing walls, batter maybe considered.
abutment. Whereused,thebattershouldbebetween
1:10and1:15(H:V).
Provide apaving notch on all on-system
structures and off-system structures that 8. Backfill.Abutmentsandwingwallsshallbe
haveapproachroadwaysthatarepavedor backfilledwithSelectBackfillspecifiedby
likelytobepaved. Ifanapproachslabwill the Geotechnical Section. The neat line
be constructed, show it on the General limitsoftheSelectBackfillshallbeshown
Layout. on the plans or described in the special
provisions. Show the Select Backfill
2. BridgeApproachJoints. Provideaterminal quantityontheroadplans.
jointorpavementreliefjointattheendof
tthheerrooaaddwwaayypoafvtehmeenbrtidisgecoanpcprertoea.chAsljaobinitf 9. RloeciantfeodrcdiinrgecSttleyelo.verIftahneeaxbpuatnmseinotncjaopi,ntalils
is not required if the entire adjacent reinforcementintheabutmentwallshallbe
pavementisasphalt. epoxycoated.
3. WwiinnggwwaallllsCsohnonuelcdtinootn.exItnegnednemroarl,eUt-hsahna3pemd 19.1.4 Semi-IntegralAbutments
behindthe rearface ofthe abutment. If
wingwallslongerthan3mareneeded,then Thesemi-integralabutment,orstubabutment,is
anauxiliaryfootingmustbeprovided. Also, MDT's typical end-bent configuration.
if longer extensions are necessary, force Transverse and longitudinal superstructure
effects in the connection between the forces are transmitted to the substructure
wingwallandabutment,andinthewingwall through radius plate steel shoes with anchor
itself, shall be investigated, and adequate bolts that allow rotation. Typically, the
reinforcingsteelshallbeprovided. backwall and wingwalls are cast around the
girderends, attachedtothe slab andisolated
4. Tahnicakbnuetsmse.ntThise3m5i0nimmmu.mwWaallllsthimcakynesbsefoorf farreomusetdh,etphielewicnagp.scaWnheeintheUr-bsehamponeodliwtihnigcwawliltsh
constantthicknessorwithabatteredfillface thebackwallandisolatedfromthepilecapor
asrequired. Typically,thenearfaceshallbe attachedtothepilecapwiththebackwallleft
verticalbut,ifconditionswarrant(e.g.,high freetorotate. Thejointbetweenthebackwall
walls,anticipatedtilting),itmaybeslightly and the pile cap facilitates raising the
battered. superstructureifsettlementoccurs.
5. ExpansionJoints. Verticalexpansionjoints
should be considered for wall lengths
exceeding30m.
1
19.1(4) SUBSTRUCTURESANDBEARINGS August2002
•
19.1.5IntegralAbutments therotationpermittedbythepilesissufficiently
high,andtheattendantendmomentsufficiently
Reference: LRFDArticle11.6.2. low,tojustifytheassumptionofapinned-end
conditionforgirderdesign. The ends ofthe
structuresarealsoassumedtobefreetotranslate
19.1.5.1 General longitudinally.
Traditionally,bridgeshavebeendesignedwith
expansionjoints and other structural releases 19.1.5.4 IntegralAbutmentDetails
that allow the superstructure to expand and
contract relatively freely with changing Integral abutments are typically constructed
temperatures and other geometric effects. using the following preferred method. The
Integralabutmentseliminateexpansionjointsin superstructure girders are set in place and
thebridgedecks,whichreduceboththeinitial anchored to the previously cast-in-place
constructioncostsandsubsequentmaintenance abutmentcap. Typically,theconcreteabovethe
costs. previously cast-in-place cap is poured at the
same time as the superstructure deck. To
Using integral abutments is effective in addresssteelgirderstability,refertoComment
accommodating the horizontal seismic forces. #2inSection19.1.5.2.
Minimumbeamseatlengthrequirementsneed
not be investigated for integral abutment Optional constructionjointsmaybeplacedin
bridges. thecaptofacilitateconstruction. Theoptional
jointbelowthebottomofbeammaybeusedon •
all integral abutment bridges regardless of
19.1.5.2 DesignCriteria bridgelength.
Thefollowingrequirementsmustbesatisfiedin Theabutmentdetails shallmeetthefollowing
allcaseswhereintegralabutmentsareused: requirements:
1. tBaycpkefislulpe.rsAtlrluctiunrteegsraslhalalbubtembeantcskffiolrledgiwridtehr 1. tWhiadnth75.0Tmhme.backwallwidthshallnotbeless
SelectBackfill.
2. CapEmbedment. Thepilingshallextenda
2. SteelGirderStability. Wheresteelgirders minimumof500mmintothecap.
areused,ananalysisofthenon-composite
girderstabilityshouldbemadetolocatethe 3. ConcreteCover. Concretecoverbeyondthe
first intermediate diaphragm to provide farthestmostedgeofthegirderattherear
stabilitypriortoandduringthedeckpour. faceoftheabutmentshallbeatleast 100
Idniapliheruagomfshtohueldanbaelypsilsa,cedanwitihnitnerm3edmiatoef mthme.paTvhiengminnoticmhumarceao.verTshhealltoalpsoflaapnpgleyotof
the end support. An analysis will most steelgirdersandprestressedI-girdersmay
likely yield a more economical, larger becopedtomeetthisrequirement.
diaphragmspacing.
4. Girder Anchorage. A minimum ofthree
holesshallbeprovidedthroughthewebsof
19.1.5.3 SuperstructureandInteriorSub- steel girders and through prestressed I-
StructureDesignCriteria girderstoallow#19barstobeinsertedto
furtheranchorthegirdertothecap. Position
Although the ends ofthe superstructure are theholessothat,whenthebarsareinserted,
monolithically attached to integral abutments, theywillbewithinthebackwallcage.
.
August2002 SUBSTRUCTURESANDBEARINGS 19.1(5)
5. Rsteiirnrfuposrcsehmalelntb.e#1T3hespamciedniamtuammasxiziemuomf 1 PainleinStpeagrcailngo.rsUesmei-ainstienggrlaelraobwutmoefnpti.lesPifloer
roefinf3o0rc0ingmms.teel Lboengi#t2u2dina@l b3a0ck0w-amlml hsopawceivnegr,sihfotuhledcnaoptisnoprrompaelrllyyeaxncaelyezded3amn;d
maximumspacingalongbothfacesofthe designed as a continuous beam, this
abutment. restrictionneednotapply. Ifpractical,one
pilemaybeplacedbeneatheachgirder. To
6. CornerBars. UseL-barsextendingfromthe reduce force effects for a large beam
rearfaceofthebackwallintothetopofthe spacing,considerationmaybegiventotwin
slabat300-mmspacingorless. pilesunderthebeam, spacedatnotlessthan
750mm. SeeChapter20forminimumpile
spacings. Thepilesareconsideredtobefree
19.1.6Free-StandingAbutments ended and capable of resisting only
horizontalandverticalforces.
19.1.6.1 Usage
Usefree-standingabutmentswhereintegraland 2. Nleusmsbteharn.foTuhr,eunnulemsbserotohefrpwiilseesasphaplrlovneodtbbye
semi-integral abutments cannot accommodate theBridgeAreaEngineer.
themagnitudeofthe longitudinalmovements.
pFirleees-,sdtrainldliedngshaafbtustomrenstpsreacdafnootbiengsf.ounded on 3. Oshvaellrhbaen4g5.0mTmh.e minimum cap overhang
19.1.6.2 Epoxy-CoatedSteel 19.1.7.2 Pile Design for Integral/Semi-
IntegralAbutments
Forabutmentsthathaveabridgedeckexpansion
jointlocatedbetweentheendofthedeckandthe Thefollowingcriteriaapplyspecificallytopiles
faceofthebackwall,allreinforcingsteelinthe and loads at integral and semi-integral
abutmentshallbeepoxycoated. Thisincludes abutments:
all cap, backwall and, if present, wingwall
reinforcing. 1. Loads/Forces. Forstructuressatisfyingthe
requirements provided in Section 13.4.4,
force effectsintheabutmentpiles dueto
19.1.6.3 SeismicShearBlocks temperature,shrinkage,creepandhorizontal
earthpressuresmaybeneglected.
Inseismicareas,shearblocksmaybeformed
into the top ofthe abutment cap to provide Analternativeanalysismustbeusedifthe
lateralrestraintforbeamsthatdonothaveside criteriainSection13.4.4arenotmet. The
restraint provided by the bearings or other followingstepsshouldbeconsideredinthis
means. analysis:
a. The point of zero superstructure
19.1.7PileSpacingsandLoads movement should be established by
consideringtheelasticresistanceofall
19.1.7.1 GeneralDesignCriteria substructuresandbearingdevices.
Thefollowingcriteriaappliestopilingforboth b. The effects of creep, shrinkage and
integralandsemi-integralabutments: temperatureshouldbeconsidered.
19.1(6) SUBSTRUCTURESANDBEARINGS August2002
•
c. Any movement at any point on the Ifpilescannotbedrivenaminimumof3m
superstructureshouldbetakenasbeing intonaturalgroundduetoarockstratum,
proportionaltoitsdistancetothepoint socketthepilesintoundersizedholesdrilled
ofzerodeflection. into the rock. The diameter of the
undersized holes shall equal the inside
d. Lateral curvature ofthe superstructure diameterofthepipepile,ifpipepilesare
may be neglected if it satisfies the used,or25mmlessthanthemaximumpile
provisions of Article 4.6.1.2 of the dimensionforsteelH-piles. Socketthe
LRFDSpecifications. pile a minimum of 1 m into the rock
formation;thepileshouldextendatleast3
e. Vertical force effects in the abutment mbelowthecap.
pilesshouldbedistributedlinearlywith
load eccentricities properly accounted
for. 19.1.7.3 PileDesignforFree-Standing
Abutments
f. Lateral soil resistance should be
consideredinestablishingforceeffects The following criteria apply to piles at free-
andbucklingresistanceofpiles. standingabutments:
g. Force effects should be combined in 1. PileSpacing. Atleasttworowsofpilesor
accordance with the provisions of batteredpilesmustbeprovidedtoprovide
Article 3.4.1 ofthe LRFD Specifica- the necessary longitudinal stiffness. The
tions. minimumpilespacingis750mmparallelto #
thecenterlineoftheabutment.
2. PileType. OnlysteelH-pilesorsteelpipe
piles are permitted at integral abutments. 2. Batter. Uptoone-halfofthepilesmaybe
Forsemi-integralabutments, steelH-piles, batteredtoincreasetheoverturningstability
steel pipe piles or fluted steel piles are ofthestructure.
permitted. TheorientationofsteelH-piles
(strong versus weak axis) is a design 3. Movement. Theeffectsofthemovements
consideration, anditispreferablethatall due to overturning pressures or lateral
pilesbe orientedthe same. Allabutment pressuresshallbeinvestigated(e.g.,ensure
pilingshallbedrivenverticallyandonlyone thattheclosingofjointsdoesnotoccur).
rowofpilingispermitted.
3. PmiilneimDruimvionfg.3 mPiilnestosnhaatlulralbegrodurnidv.en Iaf 19.1.8Wingwalls
pilescannotbedriventothisdepthduetoan Reference: LRFDArticle11.6.1.4
existing cohesive earth stratum, with a
standard penetration resistance (N) Wingwalls shall be of sufficient length and
exceeding 35 blows per 305 mm located depthtopreventtheroadwayembankmentfrom
withthe3mintervalbelowthebottomof encroaching onto the stream channel or the
the cap, the piles shall be placed in defined clear opening. Design the wingwall
oversized, predrilled holes before driving. lengthstokeeptheembankmentatleast300mm
bTehe10d0iammemtegrreoaftetrhethoavnertshiezmedaxhoilmeusmshcoruolsds bGeenleorwalltyh,etbheeaslmopeseoatftohreftilhlewitlolpnootfbethseteceappe.r
sectionaldimensionofthepile. Theholes than2:1 (H:V), andwingwalllengthswillbe
shall be backfilled with uncrushed base establishedonthisbasis.
courseaggregatesize 17mm(peagravel)
followingthepiledrivingoperation.
August2002 SUBSTRUCTURESANDBEARINGS 19.1(7)
Withrespecttoabutments,thefollowingapplies furnishingandinstallingmostsystems canbe
towingwalls: absorbedinthecostofselectbackfill.
1. PileSupported. Ifturnbackwingwallson Static ground water levels should always be
rigidabutmentshaveatotallengthofmore considered while evaluating an appropriate
than 3 m, auxiliary pile footings for drainagesystem. Drainagesystemsshouldnot
wingwall support should be investigated. beinstalledtoallowpressurizedbackwaterto
Pile-supportedwings shallbe avoided for saturatetheabutmentbackfillduringhighwater
integralbackwalls. events.
2. wCionngnweactlilosnssh.ouldnIontexgteennedramlo,reUt-hsahna3pemd Gseunpeproarltleyd,onfionrtegrraellaotrivseelmyi-instheaglrlalowabugtimrednetrss
behindtherearface ofthe abutment. If withstraightwingsorturnbackwingslessthan3
wingwallslongerthan3mareneeded,force mlong,selectbackfillwillbeallthatisneeded
effects in the connection between the topromotegooddrainage.
wingwallandabutment,andinthewingwall
itself, shall be investigated and adequate Forbridgeswithtallerabutmentwalls,girders
reinforcingsteelbeprovided. Forrigidfree- deeperthan 1.5 m or abutments with atotal
standingabutments, the forces aremerely heightofmorethan2.5mfromthebottomof
due to permanent loads and live-load pilecaporfootingstothetopofthebackwall
surcharge. For flexible abutments, other should be given consideration for additional
transient loads must be considered in drainage features. If a drainage system is
additiontothepermanentloads. determinednecessary,aperforateddrainagepipe
placed at the base ofthe abutment wall or
3. Thickness. Theminimumthicknessofany footingispreferred. Thepipeshouldbeplaced
wingwall with an abutment shall be 350 insideafreedraininggravelmedia,wrappedin
mm. drainagefabricandslopedtodraintoapoint
outsidetheabutmentwalls.
4. Design. Unattached wingwalls shall be
designedasretainingwalls. The other systems identifiedmaybeusedto
addresssite-specificneedswithapprovalbythe
5. Concrete. For wingwalls, use Class DD BridgeAreaEngineer.
concrete.
19.1.10Joints
19.1.9Drainage
19.1.10.1 ConstructionJoints
Provide positive drainage as needed in the
embankmentbehindtheabutmentandwingwalls Toaccommodatenormalconstructionpractices,
byusingselectbackfill,weepholes,perforated the designer should indicate the following
drainpipe, amanufacturedbackwall drainage horizontal construction joints on the plans.
system or a combination of these options. MDT does notuse shearkeys forhorizontal
Include provisions for select backfill in all constructionjoints:
abutment designs in accordance with the
geotechnical recommendations in the 1. In semi-integral abutments, a horizontal
GeotechnicalReport. constructionjointshallbeindicatedbetween
• thebottomofslabfilletandthetopofthe
Providedetailsoftheselecteddrainagesystem backwall.
on the bridge plans. Generally, the cost of
19.1(8) SUBSTRUCTURESANDBEARINGS August2002
2. In integral abutments, in addition to the
construction joint indicated between the
bottom ofslab fillet and the top ofthe
backwall, a horizontal construction joint
shallalsobeindicatedatbeamseat.
3. In free-standing abutments, a horizontal
constructionjointshallbeindicatedonthe
drawings between the top ofthe cap or
footing and the bottom ofthe backwall.
Some expansion joint types may require
anotherconstructionjointatthebottomof
thepavingnotch.
4. Inturnbackwings,ahorizontalconstruction
jointshallbeindicatedatanelevationthe
sameasthetopofthecap.
Plannedverticalconstructionjointsarenormally
associated with phase construction issues or
perhapscloseproximitytoanexistingstructure.
Provision needs to be made for splicing or
mechanical rebar couplers on horizontal
rsehionuflodrcbiengatslteeaesl.t75Vmermticfarlomretihnefocrocnisntgrucsttieoenl fVjVll
joint.
19.1.11Concrete
Use Class DD concrete for all substructure
components.
