资源描述:
《construction of marine and offshore structures(third edition)(3-3)》由会员上传分享,免费在线阅读,更多相关内容在学术论文-天天文库。
1、13PermanentlyFloatingStructures13.1GeneralThesearestructuresthatareintendedtoremainfloatingduringtheirservicelife.Theymaybemoored.Theymayberelocatedduringservice,ortheymaybeself-propelled.Thisisaconceptofgreatpotentialforthefutureascoastallandbecomesincreasinglyunavailabl
2、e,forcingustoutilizeoceanspace,despitethedifficultiesimposedbytheenvironment.Sincemanyofthestructuresareoilstoragevessels,whichfloatwithvaryingfreeboard,evenwhenpartialballastingiscarriedout,theirmooringmustgivethoroughconsider-ationtotransversewindforces.Thisisespeciallyt
3、rueofsteelvesselsbecauseoftheirinherentsmalldraftwhenempty.Concretevessels,ontheotherhand,havegreaterinherentdraftbutmorelimitedcapacity,especiallyinshallowwater.Typically,thesepermanentlymooredvesselsemploysingle-pointmoorings,butinsomeareasofshallowwater,fixedmooringsar
4、eused.Storagevesselsforoilareusuallyequippedwithbothaballastingsystemandatransfersystem.Althoughtheclassificationsocietiesrequiredrydockingforbottominspectioneveryyear,theywillusuallywaivethatrequirementforfiveyearsifanannualunderwaterinspectionrevealsnodefects,especiallyf
5、orconcretevessels.Thismeansthatcleaningofthehullalsohastobecarriedout,byhigh-pressurewaterjet,supplementedbywirebrush.ThegreatmajorityoftheseoilstoragevesselsaresteelshipswhoseconstructionareinaccordancewithInternationalRulesofIMPCOandShipClassificationSocietiessuchasABS,
6、DNV,BureauVeritas,andLloyds.Manyofthesesteelvesselsnowarerequiredtohavedoublehulls.Thedesign,construction,andmaintenanceiswellcoveredbytherulesoftheclassificationagencies,sowillnotbefurthercoveredhere.Concretefloatingstructureshaveahistoryofequallongevity,thefirstuseofreinf
7、orcedconcretebeingasmallboat.However,theyhavehadonlysporadicdevelopmentsince,duetotheirinherentweight.However,duringWorldWarsIandII,anumberofsmallreinforcedconcretetankersandoilstoragebargeswerebuilt,duetotheshortageofsteel.Floatingbridgesofconcrete,floatingpiers,ferrysli
8、pdocks,floatingguidewallsfornavigationlocks,andlargefloatingstorageandproductionvesselshavebeenconstructe