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HansDeBacker,AmelieOuttier,PhilippeVanBogaert
2.THEINSTALLATIONOFASPHALTLAYERS
ONTHEORTHOTROPICDECK
Oneofthemostlogicalsolutionsfortheabovementionedfatigue
problemsistheuseofanasphaltlayerasadispersionlayer.Sincemostroad
bridgesareequippedwithasphaltlayersanyhow,anypositiveinfluenceofthis
layerwouldbegreatlybeneficialinimprovingthefatiguebehavior.
Tostudy,theinfluenceofanasphaltlayeronanorthotropicbridgedeck,a
finiteelementmodelwasdeveloped.Formostpreviousfiniteelementmodels
forasphaltcalculations,linearelasticmaterialmodelswereused,howeverto
modeltheasphaltlayerascorrectlyaspossible,avisco-elasticmaterialmodel
wasdeveloped
ThebestmaterialbehaviorlawforbituminousmaterialsistheBurgers
model,incorporatingnotonlytheloadingfrequency,butalsothephase
distortionwhichexistsinthestress-strainrelationshipforavisco-elastic
material,thusenablingthestudyofthedegradationofthematerialoverlonger
timeperiods.However,sincetheBurgersmodelcannotbeusedintheavailable
finiteelementsoftware,i.e.SAMCEF,theclosestapproximationwasused.The
ZenermaterialmodelusesaYoung’smodulusE*,incorporatingthedependency
ofasphaltontheambienttemperatureaswellasontheloadingfrequency.This
simplificationshouldnotradicallyinterferewiththecalculationofthemaximum
occurringstressrangeintheconsideredweldingdetail.
η
1
E
1
E
2
E
a)LinearElastic
MaterialModel
b)Zener
MaterialModel
η
2
η
1
E
1
E
2
c)Burgers
MaterialModel
Fig.2.Differentpossiblematerialmodelsforasphaltlayers
