海工建造规范培训(DNV建造标准)C401中文版.ppt

DNV OS C401 FabricationandTestingofOffshoreStructures JonR Hansen2007 04 16 Version Slide2 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures Thisiswhat sallabout Version Slide3 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures CoursePurpose 培训目的TogiveabriefoverviewofDNVoffshorestandards 介绍DNV海工标准TogivebasicknowledgeoffabricationstandardOSC 401介绍海工建造标准OSC 401的基础知识 Version Slide4 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures DNV sROLEINOFFSHORECLASSIFICATIONDETNORSKEVERITAS DNV isanautonomousandindependentfoundationwiththeobjectivesofsafeguardinglife propertyandtheenvironment atseaandonshore DETNORSKEVERITAS 简称DNV 是一家独立的公司 致力于在海上或海岸上保护工作人员的生命 公共财产及设备的安全和对环境进行保护 DNVundertakesclassification certification andotherverificationandconsultancyservicesrelatingtoqualityofships offshoreunitsandinstallations andonshoreindustriesworldwide andcarriesoutresearchinrelationtothesefunctions DNV提供在下列领域内为客户提供分级 验证 认证和咨询服务 造船 海工部件和安装 海岸工程以及在这些相关领域的专业研究 Version Slide5 15 03 2020 OffshoreStandards海工标准包括 DNV OS C401 FabricationandTestingofOffshoreStructures A QualityandSafetyMethodology质量和安全控制方法 B MaterialsTechnology材料技术 C Structures结构 D Systems系统 E SpecialFacilities特殊设备 F PipelinesandRisers安装管道和竖管 A B C D E F Version Slide6 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures OffshoreStandards 海工标准ProvidetechnicalprovisionsandacceptancecriteriaforgeneralusebytheoffshoreindustryaswellasthetechnicalbasisforDNVoffshoreservices 海工标准为海工建造提供技术条款和可接受的标准 Version Slide7 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures RecommendedPractices ProvideproventechnologyandsoundengineeringpracticeaswellasguidanceforthehigherlevelOffshoreServiceSpecificationsandOffshoreStandards 提供技术和录音实例以及提供高水平的海工服务规格和海工标准指南 Version Slide8 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures DNVOffshoreCodesareofferedwithinthefollowingareas A Qualification QualityandSafetyMethodology资格 品质和安全控制方法B MaterialsTechnology材料技术C Structures结构D Systems系统E SpecialFacilities特殊设备F PipelinesandRisers安装管道和竖管G AssetOperation资产管理H MarineOperations海工运营 Version Slide9 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures DifferenceShipRulesversusOffshorerules船舶规范与海工规范不同的原因RulesforOffshoreprojectsareinsomeareasquitedifferentfromthetraditionalShipRules duetolongtimeonlocationwithnoorlimitedpossibilitiesleavethelocation 20 25yearsservicetime 海工产品必须在海上持续工作20 25年船舶可以进坞进行检验 中间检验 特检 Version Slide10 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures Someimportantaspects 几个重要方面Structuralintegrityandstrength Loadsbasedonenvironmentalconditionsonactuallocation 结构形式和强度 载荷根据工作地点的实际环境 AccidentalloadstobeincludedinDesignLoads DAL 设计载荷还考虑到可能受到的意外载荷Fatigue attentiontodetails 疲劳问题Maintenance保养维修Corrosionprotection防腐Inserviceinspection Accessetc shouldbeplannedandprovidedduringnewbuildingphase 使用过程中的检验IncreasedreliabilityofMarinesystems utilitysystemsandequipment 提高各种系统和设备 设施的可靠性Safetysystems Fire explosion abandoninstallationetc 防火 防爆 逃生等安全系统Shelfstaterequirementstoaccommodationandworkingenvironment当地的居住和工作环境要求 Version Slide11 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures DNV OS C401 FabricationandTestingofOffshoreStructures DNV OS C401海工结构建造和试验CH 1INTRODUCTION介绍CH 2TECHNICALPROVISIONS技术条款CH 3CERTIFICATIONANDCLASSIFICATION验证与入级 Version Slide12 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures CH 1INTRODUCTIONA200Objective201Theobjectivesofthisstandardareto Provideaninternationallyacceptablestandardtoensurethequalityofallweldingoperationsusedinoffshorefabrication throughidentifyingappropriateweldingprocedures welderqualificationsandtestmethods 提供国际认可的标准 通过对焊接程序 焊工资格和测试方法的认证来保障海工焊接质量Serveasatechnicalreferencedocumentincontractualmattersbetweenpurchaserandcontractor 为买方和承包人就合同问题提供技术参考文件Serveasguidelinefordesigner purchaserandcontractor为设计者 买方和承包商提供指导SpecifyminimumrequirementsforweldingoperationssubjecttoDNVcertificationandclassification 将焊接工作的要求最细化 使其符合DNV的认证和分级要求 Version Slide13 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures Chapter2Technicalprovisions第二章 技术条款Sec 1WeldingProceduresandQualificationofWelders焊接工艺和焊工取证Sec 2FabricationandTolerances建造与公差Sec 3Non DestructiveTesting无损探伤Sec 4OtherTests其它试验Sec 5CorrosionProtectionSystems防腐系统Sec 6Miscellaneous其它 Version Slide14 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures Sec 1WeldingProceduresandQualificationofWelders焊接工艺与焊工取证Weldingprocedures焊接工艺Pre WeldingProcedureSpecificationtobepreparedandacceptedbypurchaser 焊接预试验工艺必须得到船东认可WPQTtobebasedonacceptedPre WPS按照焊接预试验工艺进行焊接工艺认可试验WPSmaybebasedonpurchaseracceptedWPQTandinconformancewithanagreedqualificationscheme 焊接工艺建立在焊接工艺认可实验及其质量控制方案WPSshallreflectconditionsandequipmentusedfortheactualproductionwelding 焊接工艺须反映实际工作所使用的设备和相关条件WPSshallreflecttheworkingenvironmentfortheworkshoporsitewheretheproductionweldingwillbeperformed 焊接工艺须反映实际工作场所的工作环境SpecificrequirementstoWPQTforC MnsteelsarefoundinOS C401Ch 2 Sec 1 C 关于C Mn系钢的焊接工艺与焊工资格的具体要求 详见OS C401Ch 2 Sec 1 C Version Slide15 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures AWPScanbeestablishedbyoneofthefollowingmethods 编制焊接工艺说明书的方法 Performingofweldingproceduretest WPQT andsubsequentreviewoftheweldingprocedurequalificationrecords WPQR 进行焊接工艺评定试验 并对相关记录进行评定Reviewofpreviouslyqualifiedweldingprocedurestests WPQT whichhasbeenwitnessedbyapartyrecognizedbythepurchaser对其它船级社或其它组织认可的焊接工艺评定记录进行评定ReviewofWPS评定焊接工艺说明书Reviewandverificationofdocumentationshowingsuccessfulapplicationofweldingproceduresoveraprolongedperiodoftime 对经过长期使用后被认为是成功的焊接工艺进行评定 验证 Version Slide16 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures Weldersqualification焊工的评定Welderswhoareweldinginmanualorpartlymechanizedweldingprocessesshallbequalifiedinaccordancewitharecognizedstandard E g EN287 ISO9609 ASMEIXorANSI AWSD1 1 手工焊和半自动焊焊工须得到相关组织的认可Weldersusingfullymechanizedweldingorautomaticweldingprocesses needgenerallynotpassaqualificationtest butshallreceiveadequatetrainingforsettingandoperationofequipment 自动焊的操作人员无需进行专门的考试 但需要通过专门的培训来学会设置和操作设备 Version Slide17 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures Sec 2 Fabricationandtolerances 第二章建造与许可公差FabricationPlanning建造方案Asaprerequisiteforfabrication procedures inspectionandtestplansandworkinstructionsforexecutionandcontroloffabricationactivitiesshallbeestablished 工艺方案 检验和试验方案是执行和控制建造的先决条件ContractorsinvolvedinfabricationofstructuralmembersshallhaveadocumentedandimplementedqualitysystemaccordingtoISO9001orequivalent 承包商应该具有完善的质量体系Workmanshipshallbeinaccordancewithwrittenproceduresacceptedbythepurchaser 必须按照船东认可的工艺进行施工Allworkshallbeexecutedwithadequatecontrolbythecontractor Repairworkshallbecarriedoutinaccordancewithwrittenproceduresacceptedbythepurchaser 所有施工过程必须有严格的控制 修补工作也必须按照认可的工艺进行 Version Slide18 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures Faultsanddeficienciesshallbecorrectedbeforepaintingorothermeansofpermanentcovershavebeenapplied 所有错误和缺陷必须在油漆和其它东西覆盖前得到修复PriortocommencementoftheworkthecontractorshallsubmitaplanforNDT NDTproceduresanddocumentsforNDTinspectors certificationforacceptancebythepurchaser Theprogrammeshallcontaininformationanddocumentsforplanning controlling reportingetc AcceptancecriteriaforNDTshallbeacceptedbythepurchaseriftheyarenotspecifiedinrelevantdocuments 开工前承包商需要提供无损探伤方案 方案应包括整个过程控制和验收标准 整个方案应包括计划 控制和汇报等方面的信息和文件 如果没有特别的要求 承包商需接受NDT的验收标准 Version Slide19 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures Inspection 检验Tobecarriedoutinaccordancewithacceptedinspectionandtestplanscovering 检验要按照检验和试验方案进行 应包括 correctidentificationanddocumentationanduseofmaterials材料跟踪qualificationandacceptanceoffabricationproceduresandpersonnel评定施工人员资质和建造方案inspectionofpreparatorywork assembly fit upformwork reinforcementetc 检验成型 装配 加强等准备工作weldinginspection焊接的检验inspectionoffabricationworkforcompliancewithspecificationsandprocedures确认施工人员资质以及是否按工艺施工witnessingNDT controlandtesting跟踪无损探伤和其它试验inspectionofrepairs修补工作的检验 Version Slide20 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures inspectionofcorrosionprotectionsystems防腐系统的检验ensurefunctionalityofexaminationortestingequipmentandofrecordingand ormeasuringdevicesvitalforcorrectfunctioningofequipmentandmachineryusedinfabrication 确保检验设备的可靠性Dueconsiderationshallbegiventotheaccessandthetimerequiredforadequateinspectionduringfabrication 确保留有足够的检验时间和通道Highnon conformanceratesinexecutionoftheworkorintheproductitselfshallcallforspecialconsiderations Suchspecialconsiderationsmayinclude butnotbelimitedto increasedinspection re qualificationofpersonnelorotheragreedremedialactions 在建造过程中不按规定施工人次较多 或产品质量问题较多的情况下 需要采取增加检验 对施工人员重新评定以及其它弥补措施NOTE 注意 Inspectorsshallbequalifiedaccordingtoarecognizedschemeandshallbeabletoprovidedocumentationofproficiency 检验人员需要经过专门培训并得到认可 Version Slide21 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures MaterialIdentification CuttingandForming材料识别 切割和成型Materialidentification材料识别Atraceabilitysystemthatensurescorrectinstallationanddocumentationofthematerialgradesorstrengthclassesshallbeestablishedbythecontractorthroughouttheprefabricationandinstallationprocess 建立材料跟踪系统确保正确使用材料 记录材料 材质 等级Propercareshallbeexercisedduringhandlingandstoragetopreserveidentificationofsuchmaterial 材料识别和跟踪应贯穿下料 运输 储存等全过程 Version Slide22 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures Cuttingandforming Theeffectofworkhardeningshallbeconsideredifshearingisusedforcuttingofmaterial Specialattentionshallbepaidtotheriskofcrackededges 材料剪切后边缘会产生硬化和裂纹 要特别注意Attentionshallbepaidtoexcessivelocalhardeningandcarboncontaminationsbythermalcutting Thismaybereducedbysuitableheattreatmentorremovedbymechanicalmeans 通过热工切割可能产生的局部硬化和渗碳 可以通过热处理和机械方法消除Formingandstraighteningofmaterialsshallbeperformedaccordingtoagreedprocedures Suchworkshallbecontrolledbythecontractor 成型和校平工艺需要得到认可 并得到有效控制Thedegreeofcolddeformationofspecialandprimarystructuralelementsshallbelessthan5 Ifthedeformationexceeds5 eitherheattreatmentorstrainageingtestsshallbecarriedoutaccordingtoanagreedprocedure 主体结构和特殊结构的冷变形大于5 时 要通过认可的热处理方法校正 Version Slide23 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures Tolerances公差Allowablefabricationtolerancesshallbesubmittedtothepurchaserforacceptance 规定公差需得到船东认可Specialconsiderationsshallbegiveninprovidingproperalignmentofstructuralmembers Allowablefabricationtolerancesshallbeestablishedonbasisofdueconsiderationtothecriticalityofthedesign 特别要注意结构对中问题ThemaximumfabricationtolerancesmaygenerallybetakenincompliancewithIACSShipbuildingandRepairQualityStandardPartASec 6andSec 7 建造工程可参照国际船级社的标准PartASec 6andSec 7NOTE 注意StraightnessofmemberswhicharebasedonbucklingcalculationsaccordingtoDNV RP C201and orDNV RPC202shallbewithinthetolerancesgiveninTableE3 结构的直线度参照DNV RP C201and orDNV RPC202的E3表格106Alignmentsofthenon continuousplatesincruciformjointsandbuttweldsshallbewithinthetolerancesgiveninFig 1 TableE1andTableE2 非连续构件的对中参照以下E1 非连续 E2 连续对接 表格的标准 Version Slide24 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures 表E1表示十字接头 依次分别为 特殊结构 重要结构和次要结构的错位表E2表示对接接头 依次分别为 特殊结构 重要结构和次要结构的错位 Version Slide25 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures Version Slide26 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures Assembly Welding HeattreatmentandRepairsAssemblyandWelding 装配和电焊Assemblyandweldingoperationsshallbecarriedoutbyqualifiedpersonnelandsupervision 装配工和电焊工都必须持证Afabricationsequenceshallbeestablishedtoensurethatthestructurecanbeassembledinamannerwhichallowsforeffectivecontrolatallstagesofwork 为了对整个工程进行有效控制 必须编制建造次序Fit up preparationforweldingandweldingoperationsshalltakeplaceinaccordancewithproceduresacceptedbythepurchaser 装配 焊前准备工作 焊接都必须按认可的工艺进行Theweldingsequenceshallbesuchthattheamountofshrinkage distortionsandresidualstressesareminimized 焊接顺序要有利于焊接变形和残余应力的最小化 Version Slide27 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures Thefit upshallbecheckedfordimensionalaccuracybeforewelding Surfacestobeweldedshallbefreefrommillscale slag rust grease paintetc Edgesaretohaveasmoothanduniformsurface Noweldingshallbeperformedwhenthesurfacesaredamp Suitableprotectionshallbearrangedwhenweldingisperformedduringinclementweatherconditions Thegrooveshallbedryatthetimeofwelding 焊接前必须检验装配的准确性 焊接区域必须清除氧化皮 熔渣 铁锈 油渍 油漆等 板缝必须保证平直 严禁在潮湿的板缝上焊接 焊缝必须保持干燥 天气恶劣的情况下 焊接前要采取适当的防护措施 Preheatingshallpreferablybeperformedwithelectricheatingelements Gasburnersmaybeusedundercontrolledconditions Cuttingtorchesshouldnotbeused 当板缝需要加热时 最好使用电加热 烘枪的使用必须在严格控制下进行 严禁使用割刀加热 Forweldsofstructuralcategoryspecial primaryandbutt weldsinsecondarystructuralelementsaWPSshallbeestablishedforacceptancebythepurchaser 主体结构 重要结构焊接的焊接工艺以及次要构件的对接缝的焊接工艺必须得到船东的认可 Version Slide28 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures Guidancenote Theweldconnectionbetweentwocomponentsshallbeassignedthestructuralcategoryareaequaltothehighercategoryofthejoinedcomponents Forstiffenedplatesnotclassifiedasstructuralcategoryspecial theweldconnectionbetweenstiffenerandstringerandgirderwebtoplatemaynormallybeassignedstructuralcategorysecondary 两个构件焊接时 按照较高等级的材料的焊接要求进行 非重要构件的扶强材的焊接 平台扶强材的焊接 桁材扶强材的焊接 扶强材之间的焊接都可以按照次要构件的焊接要求进行 Tackweldingshall whenintegratedinproductionwelding bequalified Forweldsspecifiedin112aWPSshallbesubmittedtothepurchaserforacceptance 定位焊作为结构焊的一部分时 点焊工或焊工必须持证 对于112项规定的焊接 焊接工艺需要得到船东的认可 Allfabricationweldingshallbeperformedwithinthelimitsofessentialvariablesofthequalifiedweldingprocedure Thisalsoincludestackwelding sealwelding weldingofliftinglugsandattachmentweldsaswellasrepairwelding 所有的焊接都不能超过认可的焊接工艺范围 这包括 定位焊 盖面 吊耳和其它附件的焊接以及电焊修补工作 Version Slide29 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures Whenresumingweldingonpartiallyfilledjointsinspecialareas preheatingshallbeperformedandthetemperaturewithinthespecifiedtolerances shallifnototherwiseagreed beequaltotheinterpasstemperaturefortheweldingpassinquestion 在多道焊焊缝未一次性焊完的情况下 继续施焊前需要按要求对焊缝进行加热 加热温度要符合规定要求或等同于同类焊缝的层间温度 Groovesproducedbygougingshallbefollowedbygrindingremovingcarbonizedmaterialandthegrooveshallbedressedtoashapeconsistentwithtolerancesinagreementwiththepurchaser 碳刨坡口要用打磨的方法去除渗碳层 坡口成型的公差范围也要得到船东的认可 Weldingconsumablesshallbeclassifiedwithrespecttostrength applicationareaandhydrogenlevelaccordingtorecognizedscheme 焊材的使用要按照规范 符合强度 焊接位置的要求 氢含量也要符合相应的要求 Version Slide30 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures Recyclingoffluxesforsubmerged arcweldingshallbeperformedinamannerthatensuresamixtureofnewandusedfluxwithcontinuallyhomogenousproperties 焊剂的回收利用以及新老焊接的混合使用要保证焊剂的纯度 Weldsshallbeterminatedinamannerthatwillensuresoundweldswithoutend craters Extensionbarsandrun offplatesshallberemoveduponcompletionandcoolingoftheweld Theendoftheweldshallbemadesmoothandflushwiththeedgesofabuttingparts 起弧和息弧分别要使用 确保两端没有弧坑 引弧板和息弧板在焊缝冷却后去除 端头电焊要光顺 与板边保持平直 121Grindingofweldswiththeintentionofincreasingthefatiguelifeand orreducingtheprobabilityofbrittlefractureshallbecarriedoutaccordingtoagreedspecifications 用打磨的方法来提高焊缝的疲劳寿命或者消除裂纹要符合规范 Version Slide31 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures Storageandhandlingofweldingconsumablesshallbeinaccordancewiththemanufacturer srecommendations andinaccordancewithproceduresgivingdetailsregardingconditionsinstoragerooms temperatureinstorageovensandquivers lengthofexposureandconditions asapplicable 焊材的使用和保存都要得到船东认可 包括 储存室的条件 烘箱 焊条筒的温度等 Weldingproductiontestsshallbemadeduringfabricationofweldsinspecialareasandinprimarystructuralelementstoverifythattheproducedweldsareofacceptablequality Minimumonetestcouponisrequiredfromeachappliedweldingprocess 主体结构和重要结构的焊接要通过同等环境下的试验来验证其可靠性 每种结构至少做一个试验 Importantweldingoperationsshallbecarriedoutunderdailysupervisionofaninspector whohastheexperienceandqualifications whichenablehimtojudgethistypeofwork Theworkofeachweldershallberegularlyexamined 重要结构焊接要有合格的人员监控 所有焊工都要接受定期检查 Theweldingshopandcontractorsshallkeepacardindexorregisterofallapprovedwelders withallrelevantinformationregardingqualificationtests basemetal consumables weldpositions jointdesignetc 每个车间和分包商都要建立焊工目录 目录要包含 焊工通过的试验以及相应的焊材 焊接方位 接头形式等信息 Version Slide32 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures Repairs 修补Repairsshallbecarriedoutinaccordancewithqualifiedrepairproceduressubjecttoagreement 修补必须按认可的工艺进行 GuidancetorepairworkmaybefoundinIACSShipbuildingandrepairQualityStandard PartASec 9andPartB 修补工作可以参考IACS的PartASec 9andPartBMembersdistortedbyweldingmaybestraightenedbymechanicalmeansorbycarefullysupervisedapplicationofalimitedamountoflocalizedheat Theapplicationofheatormechanicalforceshallbeinaccordancewithawrittenprocedure 焊接变形的机械校正或局部火工校正必须在严格的监控下按工艺进行 Defectsinweldsmayberectifiedbygrinding machiningorwelding Weldsofinsufficientstrength ductilityornotchtoughnessshallbecompletelyremovedpriortorepair 焊接缺陷可以通过打磨 机械加工或者电焊进行修补 当焊缝没有足够的强度 延伸性或缺口韧性时 整个焊缝需要清除 进行重新焊接 Themechanicalpropertiesofrepairweldshallsatisfytheminimumspecifiedpropertiesofthesteelinquestion 电焊的修补要确保结构的机械性能 Version Slide33 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures Repairweldinginthesameareamaybecarriedouttwice Furtherrepairsshallbeevaluatedineachindividualcase 同一处电焊修补只能修补或返工两次 之后每一次修补前都必须进行评估确认 Wheneveradefectisremoved thegougedandgroundareashallbeexaminedbymagneticparticletestingorothersuitablemethodstoverifycompleteremoval用碳刨或打磨清除缺陷后 要用磁粉探伤来确认缺陷已完全清除 Thepreheatingandworkingtemperatureshallwhenmakingshallowandlocalrepairsinspecialandprimarystructuralelementsberaised50 Cabovethelevelspecifiedforproductionweldingandbeatleast100 Cunlessotherwiseagreed 主要构件和重要构件在修补前需要预热 预热温度要高于规定焊前温度50度 至少要达到100度 Forplanardefectstherepairlengthoneithersideofthedefectshallbe50mmlongerthanthesizeofthedefectasconfirmedbyNDT对无损探伤发现的缺陷进行修补时 返工的长度要确保两头都要超过缺陷长度50MM Toensuresoundrepairwelds thesinglerepairlengthshallnotbeshorterthan50mm 任何地方的焊缝修补长度都必须大于50MM Version Slide34 15 03 2020 DNV OS C401 FabricationandTestingofOffshoreStructures Minordiscontinuitiesmayberemovedbygrindingormachining makingasmoothtransitionintothesurroundingmaterial Thethicknessshallnotbereduced