DNVGL-ST-0119 Floating wind turbine structures

1 The electronic pdf version of this document, available free of chargefrom , is the officially binding GL ASSTANDARDDNVGL-ST-0119 Edition July 2018 Floating wind turbine structuresFOREWORDDNV GL standards contain requirements, principles and acceptance criteria for objects, personnel,organisations and/or operations. DNV GL AS July 2018 Any comments may be sent by e-mail to service document has been prepared based on available knowledge, technology and/or information at the time of issuance of thisdocument. The use of this document by others than DNV GL is at the user's sole risk. DNV GL does not accept any liability or responsibilityfor loss or damages resulting from any use of this document.

2 Changes - currentStandard DNVGL-ST-0119 . Edition July 2018 Page 3 Floating wind turbine structuresDNV GL ASCHANGES - CURRENTThis document supersedes the June 2013 edition of in this document are highlighted in red colour. However, if the changes involve a whole chapter,section or subsection, normally only the title will be in red July 2018 TopicReferenceDescriptionNew titleThe previous title of DNV-OS-J103 hasbeen of terminologyWhole documentThe term ship impact has beenreplaced by boat impact to align withDNVGL-ST-0437, DNVGL-ST-0126 andIEC section has been regarding follow up ofmanufacturing by third party surveyorhas been number of terms, symbols, Greekcharacters and abbreviations havebeen note on tower revised[ ]The second paragraph in the guidancenote has been of DNV GL referencedocuments[ ]

3 , whole documentNew DNV GL standards andrecommended practices have replacedDNV floater and degree of freedom(DOF) figures included[ ]The text describing typical floatersand boundary conditions has beenimproved to clarify the six degreesof freedom of a Floating turbine , andtwo new figures have been includedreplacing the previous in from safety class toconsequence class[ ]Low safety class has been removedand the other two safety classes havebeen replaced by consequence classes,adopting definitions from DNVGL-OS-E301, to avoid confusion with thesafety class of the wind of accidental limit state(ALS) revised[ ]The definition of ALS has been revised;presence of nonlinear environmentalconditions has been replaced bypresence of abnormal environmentalconditions.

4 Changes - currentStandard DNVGL-ST-0119 . Edition July 2018 Page 4 Floating wind turbine structuresDNV GL ASTopicReferenceDescriptionRequirements on model test andsoftware validation revised[ ], [ ]Requirements for model tests havebeen revised to only require modeltests for novel designs. A subsection[ ] regarding validation ofsoftware has been classes[ ]The subsection has been restructuredto clarify the environmental text has been revised andadditional items added in subsection[ ].Wind gust revised[ ]The guidance note on gust modelhas been expanded by an expressionfor reference wind speed thatcharacterizes the intensity of the additon, a guidance note has beenadded in [ ] and [ ],and subsection [ ] has spectrum[ ]An alternative regarding combinationof JONSWAP spectrums has water specification[ ]A specification related to deep waterhas been seismicity text[ ]The text about seismicity has beenexpanded, and reference to DNVGL-ST-0437 and ISO 19901-2 period of accidental loadmodified and added paragraphregarding current[ ]The title of the subsection has have been updatedThe return period for accidental loadsthe in guidance note in subsection[ ]

5 Has been changed from 1000to 500 years, see also changes insection [ ] and [ ]The subsection [ ] on currenthas been return period for accidental loadsin the guidance note in [ ] hasbeen changed from 1000 to 500 years,see also changes in [ ] and[ ]. [ ] regarding currenthas been for marine growth added[ ]A requirement related to assessmentof site specific conditions andclarification regarding structuralcomponents have been added. Changes - currentStandard DNVGL-ST-0119 . Edition July 2018 Page 5 Floating wind turbine structuresDNV GL ASTopicReferenceDescriptionStorm conditions added[ ]Highlighted that storm conditionswith high waves can cause governingextreme effect added[ ]Highlighted that coupling effects maybe categories added[ ]Load categories added andrestructuring of loads[ ]The values for load categoryenvironmental loads in ALS in Table4-1 and Table 4-2 have been revisedto abnormal.

6 A load category forprestressing (P) has been impact loads[ ]The text about ship impact loads hasbeen expanded by text carried overfrom the replaced DNV-OS-J101 Thetext about ship impact loads has condition[ ]The paragraph stating that the survivalcondition needs shorter survival timehas been specific design load cases(DLC) included[ ]Floater-specific DLCs have requirement for using the applicablecurrent model in the DLCs given inDNVGL-ST-0437 has been period for accidental loadsrevised[ ], [ ], [ ]The return period for accidental loadshas been reduced to 500 guidance for variance ofdraught[ ]Guidance added regarding effectsinfluencing the operational for wave slamming added[ ]A number of additional effects thatmay cause wave slamming have states clarified and load categoryP added[ ]Example of ALS for intact and damagestructure has been of the ultimate limit state(ULS) for abnormal loads has beenrevised and reference to DNVGL-ST-0437 added.

7 Two load factorsare given (differentiating betweenconsequence class 1 and 2).For ULS load factor set (b), loadfactors for the situation where thereis a risk for excessive dynamicexcitations have been load category P has been added,applicable for concrete structures . Changes - currentStandard DNVGL-ST-0119 . Edition July 2018 Page 6 Floating wind turbine structuresDNV GL ASTopicReferenceDescriptionRequirement related to structural crossjoints moved[ ], [ ]A requirement related to cross jointsand plate material has been moved to[ ].Guidance note on ASTM bolts deleted[ ]A guidance note related to the ASTM standard for bolts has been categorization added[ ]New subsection on structuralcategorization has been note on design of fibre ropesdeleted[ ]A guidance note related to design offibre ropes has been deleted as theinformation is available in note on decommissioningadded[ ]A guidance note related todecommissioning and methods forremoval has been related to concretestructures moved[ ], [ ]Requirements related to concretestructures have been moved from[ ] to a new subsection forconcrete structures , [ ].

8 Guidance note on optimum floaterdesign deleted[ ]Guidance note related to optimumfloater design has been deleted as itdid not give useful related to Mathieuinstability (MI) and vortex inducedmotions (VIM)[ ]MI and VIM shall be considered note revised regardingweather criterion for installation ofcomponents[ ]Guidance note on the use of sameweather criterion for installation ofdifferent components in a wind subsections on scantlings[ ], [ ]New subsections on scantlings havebeen SN-curve table[ ]Table 7-4 with criteria for selection ofSN-curves has been design fatigue factors (DFFs)Table 7-5 Requirements for design fatiguefactors in Table 7-5 have beenreplaced by new requirements whichare in compliance with requirementsfor fatigue design of bottom-fixedsupport structures for wind turbines the footnote it has been clarifiedthat inspections are by non-destructivetesting (NDT).

9 Clarification on corrosion protection[ ]Applicability of corrosion protectionstrategies have been clarified. Changes - currentStandard DNVGL-ST-0119 . Edition July 2018 Page 7 Floating wind turbine structuresDNV GL ASTopicReferenceDescriptionNew table with DFFs for steel tendonsTable 7-7 Requirements for DFFs for fatiguedesign of steel tendons have beenchanged by referring to Table 7-5 andformerly Table 7-2 have been replacedby Table 7-7 with tendon-specific on special floaterprovisions moved[ ]The subsections with special provisionsfor semi-submersibles, tension legplatforms (TLPs) and spars have beenmoved to the end of the note added[ ]Guidance note related to governingULS cases has been spectrum approach deleted[ ]Guidance related to use of combinedspectrum approach has been bending included[ ]A new subsection regarding out-of-plane bending of in-chain links hasbeen table with DFFs for mooringchains[ ]Requirements for DFF for fatiguedesign of mooring chains by referenceto general DFF requirements forsteel in have been replacedby Table 8-2 with chain-specific slack[ ]

10 Guidance regarding tendon slack hasbeen revised, and design against slackin the ALS has been allowed as analternative to designing against slackin the return period for ALS in damagecondition is reduce to 500 note included[ ]A guidance note related to typicalconfidence levels have been anchors[ ]New subsection on shared anchors hasbeen [ ]New subsection on scour and scourprevention has been rock anchors[ ]Explanatory text about prestressedrock anchors has been added forclarification. Terms have beenrevisited and nomenclature updatedfor clarification and alignment withcommon terminology for prestressedrock of floaters , whole documentColumn-stablized revised to semi-submersible, ship-shaped revised tobarge, deep-draught revised to spar.