bridge railing & deck design
DESCRIPTION
Bridge Railing & Deck DesignTRANSCRIPT
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INDOTBridgeDesignConference2013
BridgeRailing&DeckDesignExample
MichaelH.Wenning,P.E. & KurtHeidenreich,P.E.,S.E.
Bridge
Railing
Design
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BridgeRailingDesign
AASHTO17th Edition
and
prior
10kLoaddistributedover5
Appliedperpendicularattopofrail
Bridge
Railing
Design
NCHRPReportpublished
in1993
AllRailingSystemsmust
becrashtested.
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BridgeRailingDesign
RailselectiondefinedinIDM4044.01(05)MakingTestLevelDetermination
Basedon:ConstructionyearAADT
Curvature
Grade
DeckHeight
%Trucks
DesignSpeed
BarrierOffset
Bridge
Railing
Design
AASHTOManualforAssessingSafetyHardware
(MASH)
Introducedin2009
Acceptablerailingslocatedat
http://safety.fhwa.dot.gov/roadway_dept/policy_
guide/road_hardware/barriers/bridgerailings/
NCHRP350Railingsdonothavetobereplaced.
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BridgeRailingDesign
Bridge
Railing
Design
RailingDesignperAASHTOLRFDBridgeDesign
Specifications Chapter13
Intendedfordesignofrailstobecrashtested.
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BridgeRailingDesign
AASHTOCA13.3.1
Inthisanalysisitisassumedthattheyieldlinefailure
patternoccurswithintheparapetonlyanddoesnot
extendintothedeck. Thismeansthatthedeckmusthave
sufficientresistancetoforcetheyieldlinefailurepattern
toremainwithintheparapet.
BridgeRailing
Design
IDM4043.02(02)Deck
OverhangBased on observations of impacted
bridge railings, an overhang designed
according to previous AASHTO bridge
design specifications shows the desired
behavior that the overhang does not
fail if a railing failure occurs due to a
collision. Accordingly, the overhang
shall be designed for a collision force of
25% greater than the required capacity,which results in a design approximating
present satisfactory practice.
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BridgeRailingDesign
IDM4044.01(05)
For a minor bridge rehabilitation project which does
not include bridgedeck replacement or deck
wideningand the bridge currently has a crashworthy
TL4 bridge railing, the existing railing need not be
upgraded to a TL5 railing, though the warrants for
the TL5 railing are satisfied. If there is no significant
history of truck accidents, the installation of the TL5
bridge railing shall be deferred until the time of the
deck replacement or deck widening.
InterimQuestions?
Thank You!
INDOTBridge
Design
Conference
2013
September 17, 2013 2013 INDOT - Bridge Railing and Deck Design
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BridgeRailing&DeckDesign
INDOTLRFDbridgerailing&deckdesignpractice.
Theremainderofthepresentationwilldiscuss:
Sidewalkrailingapplications.
Barrierrailing
on
bridge
rehabilitation
projects.
LRFDBridge
Deck
Design
Deckdesignseemssimple,butseveralLRFD
designsectionsareinvolved:
Section3:Loads&LoadFactors
Section4:Distribution
Section5:ReinforcedConcreteDesign
Section9:Deck&DeckSystems
Section13:Railings
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LRFDBridgeDeckDesign
Bridgedeck
design
requirements
are
covered
underIDMChapter404.
Forlongitudinalbeambridges,twoconditions
arecheckedinthetransversedirectiontodesign
thedeckreinforcingsteel:
Theinteriorconditionbetweenbeams.
Theexterior
deck
overhang
condition.
LRFDBridge
Deck
Design
Interior
Interiordesignusesanequivalentstrip
method,wherewheelloadsaredistributed
overthestripwidth.
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LRFDBridgeDeckDesign DeckOverhang
Thedeck
overhang
design
requires
checking
three
cases
(LRFD
A13.4,inreverseorderforthepresentation):
DesignCase3:TheloadsspecifiedinArticle3.6.1thatoccupytheoverhangfortheLoadCombinationStrengthIlimitstate;
DesignCase2:VerticalforcesspecifiedinArticleA13.2fortheExtremeEventLoadCombinationIIlimitstate;
DesignCase1:Transverseandlongitudinalforcesspecified
inArticle
A13.2
for
the
Extreme
Event
Load
Combination
IIlimitstate.
LRFD
Bridge
Deck
Design
Deck
OverhangDesignCase3: StrengthIlimitstate
Thisiseffectivelythesamedesignprocessasthe
interiorstripusingdeadandliveloadsappliedto
thecantilever.(Onlygovernswithlargeoverhang)
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LRFDBridgeDeckDesign DeckOverhang
DesignCase
2:
Extreme
Event
IIlimit
state
(VerticalBarrierForce)
Thiscaseinvolvesaverticalloadappliedtothetopoftherailing. Forconcretebarrierrailing,thisconditiondoesnotcontrol.
Thebarrierrailinglongitudinallydistributestheforceifitisconstructedmonolithicallyandcontinuous.(IDM4043.02&3.04)
Thiscaseisapplicabletoposttyperailing.
LRFD
Bridge
Deck
Design
Deck
Overhang
DesignCase1: ExtremeEventIIlimitstate
(HorizontalBarrierForce)
DesignproceduresareinLRFDSectionA13.4.
This
presentation
will
focus
only
on
Section
A13.4.2DecksSupportingConcreteParapet
Railings
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OverhangDesignLoading
Thedeck
reinforcingsteel
mustbedesigned
toaccommodate
thecombined
momentand
tensionforce.
DesignCase
1:
Extreme
Event
IIlimit
state(HorizontalBarrierForce)
OverhangDesign
Loading
Ifcertainconditionsaremet,AASHTOallowsaneasysolutiontodeterminetheliveloading.
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LRFDBridgeDeckDesign DeckOverhang
LRFD
Bridge
Deck
Design
Deck
OverhangAyieldlineanalysisproducesthenominalrailingresistance.
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LRFDBridgeDeckDesign DeckOverhang
LRFD
Bridge
Deck
Design
Deck
Overhang
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LRFDBridgeDeckDesign DeckOverhang
LRFDCA13.4.2states,
Thecrashtestingprogramisorientedtowardsurvival
andnotnecessarilytheidentificationoftheultimate
strengthoftherailingsystem.Thiscouldproducea
railingsystemthatissignificantlyoverdesigned
leadingtothepossibilitythatthedeckoverhangis
alsooverdesigned.
How
Much
Force???Usingtherailingcapacitytodesignthedeckoverhang
reinforcingcanbeoverlyconservative.
TheIDMnowallowstheuseof1.25xFtasamaximum.
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LRFDRailingDesignForces
TheFtvalue
comes
from
LRFD
Table
A13.2
1using
the
appropriaterailingtestlevel.
LoadApplication
&
Distribution
The
collision
forces
are
distributed
over
a
distance
LcformomentandLc+2Hforaxialforce.The
distributionlengthincreasesata3045degree
anglefromthebarrierfacetothedesignsection.
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RailLoadDesignforTestLevel
CalculateRw&Lcfromayieldlineanalysis. Use
thelowerforcevaluebetweenRwor1.25xFt.
CalculateT&MattheDesignSection.
Alinearinteraction
equationistypically
usedtodesignthe
reinforcingsteelfor
thecombined
loading.
CutoffLocation
&
Bar
Development
Afterthereinforcingsteelisdesigned,any
requiredcutofflocationsmustbe
determined,andthedevelopmentlength
mustbeverified.
Therearenumerousdesignguidesavailable.
FHWAisagoodresource.
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FHWAGuide
www.fhwa.dot.gov/bridge/steel/pubs/if12052/volume17.pdf
FederalHighwayhasmany
designguidesavailablefor
downloadat:
http://www.fhwa.dot.gov/bridge
/steel/pubs/if12052/
Minnesota
Design
TablesSincethedesignvaluesarespecifictoarailtypeandtestlevel,Minnesotatabulatedthem:
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CaltransOverhangDesign
Caltrans
amended
LRFD
A13.4.2
as
follows:
Overhang
Design
Recommendations
TherearediscussionwithintheStructuresCommittee
regardingthepossibilityofdevelopingdesignaidsfor
railingloadingonoverhangsinoneofthefollowing
formats:
Tabulateddesignforcesandcriticalwalllengthsfor
INDOTRailingforeachavailabletestlevels,or
AmodifieddesignprocesssimilartoCaltrans.
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SidewalkRailingApplications
LRFDSection
13.4
providestwooptionsfor pedestrianwalkwaysrailingdependingonspeed.
IDM4044.02(03)discussesconsiderationsifsidewalksarepresent,andlikeLRFD
identifieslow
speed
as45mphorless.
SidewalkRailing
Applications
Ifthistypeisused,ashyline ispreferred.
Duringacollision,avehiclecanstillpotentially
mountthecurb.
Thisdoesnotprotectpedestriansfromfalling
intotraffic.
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SidewalkRailingApplications
Manymunicipalities
and
trail
groups
are
now
in
favorofprovidingrailingtoseparatepedestrians
fromvehiculartrafficregardlessofthespeed.
ThereappearstobeatrendtowardsthisHigh
Speedrailingsystem.
Thissystemhasthebenefitofproducingalower
structuredeadload.
JohnnyAppleseed
Memorial
Bridge
SR930overtheSt.JosephRiver,inFortWayne
WidenedexistingINDOTbridgetoextendtheriver
greenwaytrail
PF1Railing w/
pipeadded
Pedestrianrail
atcoping
Greatvisibility
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JohnnyAppleseedMemorialBridge
Thestructure
could
only
support
an
8foot
trail
width
Providedcurvedrailingtogivetheillusionofadded
widthandforbicyclepedalprotection.
JohnnyAppleseed
Memorial
Bridge
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JohnnyAppleseedMemorialBridge
Thesystem
produces
averystraighttoprail
appearance.
Pedestriansare
separatedfrom
vehiculartrafficand
bothareprotectedby
appropriate
railing
systems.
JohnnyAppleseed
Memorial
Bridge
Becausethereisstructurebehindtherailingtocarrytheshearforce,thetensioncomponentcanbereducedoreliminatedfromthedesign.
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BridgeRehabilitationRailing
Foran
existing
bridge
having
an
older
safety
shape
railingwithreinforcingthatdoesntmeetcurrentstandards,thefirststepshouldbetodetermineifitcanremain.
CommunicationwithAnnesRearicks Departmentshouldoccurearlyintheprocesstodetermineifalevelonedesignexceptionisappropriate.
Ashortformandsubmittalprocesstostreamlinetheinitialreviewisunderdevelopment.
Utilizingthe
existing
railing
will
reduce
costs,
but
every
situationisunique.
BridgeRehabilitation
Railing
Foranexistingbridgewithunacceptablerailing,
replacementwillberequired.
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BridgeRehabilitationRailing
Removeenoughof
theexistingrailing&
curbtoaccommodate
installationofthenew
railing.
BridgeRehabilitation
Railing
Olderdecksmayonlybe61/2thick.Thismakesitdifficulttoinstalltheanchorsystemwithoutdrillingthroughthedeck.
Onpastprojects,we
haveinstalled
abar
at
anangletousethebeamflangeasadrillstop.
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BridgeRehabilitationRailing
Thismethodcanalso
beusedona
reinforcedconcrete
girdersection.
BridgeRehabilitation
Railing
Openrailingonoldslabbridgesallowedsalttocorrodethebottomreinforcingsteel.
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RetrofitBarrierDrainageDetail
Withthenewsolidbarrierrailing,watercannolongerdrainofftheslabedge.
Abentonite waterstopcanbeinstalledtoensurewaterflowsthroughthenewdrainandnotalongthe
edge
where
salt
can
migrateinto
the
slab.
Bentonite Waterstop
Bentonite waterstop isreadilyavailablefrom
multiplesuppliersandisselfadhering.
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RailingAesthetic
Treatments
&
Safety
http://www.trb.org/main/blurbs/156682.aspx
Thisreportcontains
guidelinesforaesthetic
treatmentofconcretesafety
shapebarriers.
Questions?
Thank You!
INDOTBridge
Design
Conference
2013
September 17, 2013 2013 INDOT - Bridge Railing and Deck Design