Model accuracy in aseismic design of immersed tunnel

161 Pages·2008·9.61 MB·English

by  Jakob Hausgaard Lyngs

Model accuracy in aseisMic
d e s i g n o f i M M e r s e d t u n n e l
yzx
Master’s Thesis, 2008
Jakob Hausgaard Lyngs
Master of Science in Civil and Structural Engineering
The School of Civil Engineering, Aalborg University

Modelaccuracyinaseismicdesign
ofimmersedtunnel
MASTER’S THESIS
THE SCHOOL OF CIVIL ENGINEERING
MASTER OF SCIENCE IN CIVIL AND STRUCTURAL ENGINEERING
AALBORG UNIVERSITY, 2008
JakobHausgaardLyngs

PREFACE
This master’s thesis is prepared at the Master of Science Programme in Civil and
StructuralEngineeringatAalborgUniversity,Denmark. Thethesisistheoutcomeof
alongcandidateprojectonthe3rdand4thsemester. Thesubjectfortheprojectperiod
isDesignandAnalysisofAdvanced/SpecialStructures.
Thethesisconsistsofthefollowingparts:
• Mainthesis
• Appendices. Theappendicesarelocatedinthebackofthemainthesis.
• DVDwithdevelopedprograms,datafiles,animations,andapdf-versionofthe
thesiswithworkinghyperlinks. TheDVDisfoundinthebackofthethesis.
ThethesisprojecthasbeensupervisedbyAssociateProfessorLarsAndersen,whose
invaluable inspiration and tutoring have been greatly appreciated. Furthermore, the
thesis work has been inspired by the real-world immersed tunnel design experience
andknowledgeofSeniorProjectManagerMichaelTonnesen,COWI,andR&DMan-
agerCarstenS.Sørensen,COWI.Iwouldliketothankthemfortheirhighlyappreci-
atedguidance.
Thethesismayalsobefoundonthewebsitefinalthesis.hausgaard-lyngs.dk.
Aalborg,11thJune2008 JakobHausgaardLyngs
i

ABSTRACT
Thisthesisdealswiththemodelaccuracyforseismicdesignofimmersedtunnels,like
theproposedunderwaterarteryinThessaloniki,Greece.
The soil response to seismic waves is analysed in the frequency domain by means
ofthedomaintransformationmethodandthefiniteelementmethod. Theseismicre-
sponseofanimmersedtunnelandthedamageinthegasketjointshavebeencalculated
withaclosedformsolution,aWinkler-typemodel,andafullthree-dimensionalcon-
tinuummodel. TheWinklermodelandthecontinuummodelareappliedinthetime
domain.
FocusisespeciallygiventothedivergingresultsfromtheWinklermodel,commonly
usedinseismicdesign,andthecontinuummodel,whichisconsideredtobemoreac-
curate. Through comparative analyses it is shown that the presented Winkler model
isnotabletomodelretroactionfromthetunneltothesoil. Thisentailsthatthepre-
sented Winkler model is not suited for seismic design of an immersed tunnel with
non-uniformcrosssection.
Sensitivity analyses are performed to analyse the influence of the many parameters
whichmustbedeterminedforaseismicdesign. Itisshownthatthestratificationand
thesoilparameters,togetherwiththeearthquakemagnitude,influencesignificantlyon
the tunnel damage. On the other hand, the modelling of the immersed tunnel gasket
jointshasverylittleinfluenceonthecalculatedgasketdeformation.Finally,itisshown
thatthecriticaldirectionofwavepropagationisanangleofapproximately45◦ tothe
tunnelaxis.
iii

RESUMÉ
Dette afgangsprojekt omhandler modelusikkerheder ved jordskælvsdesign af sænke-
tunneler,medensænketunneliThessalonikiiGrækenlandsomcase.
Jordens respons som følge af jordskælvsbølger er analyseret i frekvensdomæne ved
hjælp af domænetransformationsmetoden og finite element metoden. Responset af
sænketunnelenogskaderneikoblingernemellemtunnelelementerneerberegnetmed
en løsning på sluttet form, en model af Winkler-typen samt en fuld tredimensionel
kontinuummodel. Analysernemeddesidstetomodellerforegåritidsdomæne.
Winkler-modellen anvendes ofte ved jordskælvsdesign, mens kontinuummodellen er
ansetforatværemerenøjagtig. Detomodellergivermegetforskelligeresultater,og
årsagentildenneforskelerundersøgtnøje. Gennemsammenlignendeanalysererdet
vist,atdenopstilledeWinkler-modelikkeeristandtilatmodelleretilbagekoblingfra
tunnelentiljorden. DetteindebæreratdenopstilledeWinkler-modelikkeeregnettil
atdesigneensænketunnelmedfleksiblekoblingermodjordskælv.
Veddesignmodjordskælverdermangeparametrederskalbestemmes. Foratunder-
søgehvornøjagtigtdisseparametrebørbestemmeserderudførtfølsomhedsanalyser.
Detervistatlagdelingen,jordensparametresamtjordskælvetsstørrelseharstorind-
flydelsepådenberegnedeskadepåtunnelen. Pådenandensidehardetmegetlillebe-
tydningforskadenpåtunnelen,hvordandetvælgesatmodellerekoblingernemellem
tunnelelementerne. Endelig er det vist at den kritiske udbredelsesretning for jord-
skælvsbølgenerenvinkelpåomtrent45◦medtunnelenslængdeakse.
v