bridge railing & deck design

7/18/2019 Bridge Railing & Deck Design

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INDOTBridgeDesignConference2013

BridgeRailing&DeckDesignExample

MichaelH.Wenning,P.E. & KurtHeidenreich,P.E.,S.E.

Bridge

Railing

Design

September 17, 2013 2013 INDOT - Bridge Railing and Deck Design


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BridgeRailingDesign

AASHTO17th Edition

and

prior

10kLoaddistributedover5

Appliedperpendicularattopofrail

Bridge

Railing

Design

NCHRPReportpublished

in1993

AllRailingSystemsmust

becrashtested.



3/28

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.



4/28

BridgeRailingDesign

Bridge

Railing

Design

RailingDesignperAASHTOLRFDBridgeDesign

Specifications Chapter13

Intendedfordesignofrailstobecrashtested.



5/28

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



7/28

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.



9/28

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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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.



12/28


LRFD

Bridge

Deck

Design

Deck

OverhangAyieldlineanalysisproducesthenominalrailingresistance.



13/28


LRFD

Bridge

Deck

Design

Deck

Overhang



14/28


LRFDCA13.4.2states,

Thecrashtestingprogramisorientedtowardsurvival

andnotnecessarilytheidentificationoftheultimate

strengthoftherailingsystem.Thiscouldproducea

railingsystemthatissignificantlyoverdesigned

leadingtothepossibilitythatthedeckoverhangis

alsooverdesigned.

How

Much

Force???Usingtherailingcapacitytodesignthedeckoverhang

reinforcingcanbeoverlyconservative.

TheIDMnowallowstheuseof1.25xFtasamaximum.



15/28

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:



18/28

CaltransOverhangDesign

Caltrans

amended

LRFD

A13.4.2

as

follows:

Overhang

Design

Recommendations

TherearediscussionwithintheStructuresCommittee

regardingthepossibilityofdevelopingdesignaidsfor

railingloadingonoverhangsinoneofthefollowing

formats:

Tabulateddesignforcesandcriticalwalllengthsfor

INDOTRailingforeachavailabletestlevels,or

AmodifieddesignprocesssimilartoCaltrans.



19/28

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



21/28

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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Removeenoughof

theexistingrailing&

curbtoaccommodate

installationofthenew

railing.


Railing

Olderdecksmayonlybe61/2thick.Thismakesitdifficulttoinstalltheanchorsystemwithoutdrillingthroughthedeck.

Onpastprojects,we

haveinstalled

abar

at

anangletousethebeamflangeasadrillstop.



25/28


Thismethodcanalso

beusedona

reinforcedconcrete

girdersection.


Railing

Openrailingonoldslabbridgesallowedsalttocorrodethebottomreinforcingsteel.



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27/28

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


bridge railing & deck design

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