Table Of ContentStressed Skin Design
in Offshore Modules
A comparative study
Tom Damen
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Stressed Skin
Design in
Offshore
Modules
A comparative study
by
Tom Damen
toobtainthedegreeofMasterofScience
attheDelftUniversityofTechnology,
tobedefendedpubliclyonDecember14,2016,at16:00hours.
Studentnumber: 4011198
Projectduration: October5,2015–December14,2016
Thesiscommittee: Prof.ir.F.S.K.Bijlaard, TUDelft,chairman
Ir.R.Abspoel, TUDelft,StructuralandBuildingEngineering
Dr.ir.P.C.J.Hoogenboom, TUDelft,StructuralMechanics
Ir.E.Boender, Iv-Oil&Gas
Ir.R.Teuling, Iv-Oil&Gas
Anelectronicversionofthisthesisisavailableathttp://repository.tudelft.nl/.
Preface
Thismaster’sthesisdealswiththedifferentwaystodesignoffshoremodulestructures. Thestudyhasbeen
carried out between October 2015 and December 2016 at the office of Iv-Oil & Gas in order to obtain the
degreeofMasterofScienceattheDelftUniversityofTechnology.
Withoutthehelpofothers,Iwouldneverhavebeenabletocompletethework. Therefore,Iwouldliketo
expressmygratitudetoProf.Ir.F.S.K.Bijlaard,Ir.R.Abspoel,andDr.Ir.P.C.J.Hoogenboomforsupervising
andguidingmethroughtheprocessofthismaster’sthesis.
Iwouldalsoliketothankmyco-workersattheofficeofIv-Oil&Gasfortheirsupport. Inparticular,Iwould
liketothankIr.E.BoenderandIr.R.Teulingfortheirconstructiveinput.
Lastly,Iwouldliketothankmyfamilyandfriendsfortheirsupport.
TomDamen
Papendrecht,November2016
iii
Abstract
Offshorewindpowerprovidesanalternativetofossilfuelswhilenegatingtheeffectofvisualandauditive
distortionofonshorewindturbines. Locatedseveralkilometresoffshore,thetransmissioncableresistance
becomessubstantial.Tolimitthelosses,thevoltageinthecablesisincreasedinasubstation.Asthisstructure
isoftenthelargestinawindfarm,profitscanbeexpectedwhenoptimizingthistopsidestructure.
Topsidestructuresfortheoil&gasindustrygenerallyrequiretobeventilatedinordertopreventgasstacking.
Theequipmentinthesubstationmodule,however,isvulnerableforthecorrosiveseaenvironment. There-
fore,thestructureneedstobesheltered. Hereby,thequestionrisesifaweightreductioncanbeobtainedby
incorporatingtheshelterinthestructuraldesign.
ThethesisiscarriedoutatIv-Oil&Gas,whoprovidedthebasisofacomparativecasestudy.Fortheresearch
tobegenerallyapplicable, thecasestudydesignissimplified. Thenaframeformthesimplifiedmodelis
chosenasabasisforthecomparison.Forasinglegoverningloadcombination,twodesignsareconstructed:
abeam-columndesigncomplyingtotheconventionaloil&gasdesignpracticeandastressedskindesign
thatincorporatestheshelteringwallasastructuralelement.
Both of the designs are then compared on steel mass and weld labour. The stressed skin design is found
tobeconsiderablylighterthanthebeam-columndesign. However,intermsofwelds,thestressedskinde-
signconsistsofahigherweldvolumeandahigherweldpasslength. Theseaspectscontributetothetotal
manufacturingcostsofthedesign.
Concluding,bothofthedesignshavetheiradvantagesanddisadvantages. Itismadeclearthatapplyingthe
dividingwallasastructuralelementintheformatofastressedskindesignprovidesacompetitivedesignin
termsofstructuralmassandweldlabour. Thefinalconclusionsbasedonthecomparisonmayvarydepen-
dentontheresourcesavailableatthemanufacturer.
v
Contents
ListofFigures ix
ListofTables xi
ListofAbbreviations xiii
1 Introduction 1
1.1 Companyandthesisbackground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Objective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.3 Substationdesign . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.4 Thesisoutline&boundaryconditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2 Literaturereview 9
2.1 Books&theses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2 Papers&codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3 Numericalmodelling 11
3.1 NumericalmodellinginSACS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.2 NumericalmodellinginAnsys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4 Designrequirements 23
4.1 Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.2 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.3 Loadingconditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.4 Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.5 Loadcombinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.6 Supportconditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4.7 Failurecriteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4.8 Fatigue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
5 SimplifiedBeam-ColumnDesign 31
5.1 Geometryandloading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
5.2 Memberresults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
5.3 Frameloading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
6 Variantstudy 37
6.1 Inputforallmodels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
6.2 Beam-columndesigninSACS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
6.3 Beam-columndesigninAnsys. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
6.4 Stressedskindesign . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
7 Comparison 49
7.1 Softwarecomparison . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
7.2 Comparisonofdesigns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
8 ConclusionsandRecommendations 57
8.1 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
8.2 Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
vii
viii Contents
Appendices
A Literaturereview 61
A.1 Books . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
A.2 Previouslyconductedtheses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
A.3 Papers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
A.4 Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
A.5 Platebuckling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
B AnsysAPDLtestscript 89
C SACSoutput 91
C.1 Simplifiedbeam-columndesign . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
C.2 Beam-columndesign . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
D Ansysoutput 111
D.1 Beam-columndesign . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
D.2 Stressedskindesign . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
E Handcalculations 119
E.1 HandcalculationstoverifytheSACSmodel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
F Numberofweldpasses 125
Bibliography 129
Description:B Ansys APDL test script. 89. C SACS output. 91 . 6.6 Joint details including the diamond plate and the widened flanges and stiffeners 43.
