phase 4 report - DNV

RN02: DESIGN OF FLOATING STRUCTURES IN ICE // PART 4 Guidance Document: Additions and Amendments to ISO 19906:2010(E)Barents 20203.86 (new)stationary floating structurefloating units kept in position by moorings ordynamic positioning,EXAMPLES: ship-shaped vessels, spar or buoyshaped platforms5 General requirements andconditions5.3 Site-specific considerations5.3.2 Long-term Climate ChangeChanges in storm frequency and magnitude, iceconditions, ocean circulation, air temperatures,permafrost, wave heights and water levels canoccur during the design service life of the structure.Consideration for such changes should be includedin the design.Site-specific assessments shall be made with regardto potential consequences of the long-term climatechange and variability. They shall include, asminimum:––change in magnitude and persistenceof the metocean and ice conditions;––change in frequency of iceberg invasionto the area of operations; and––representativeness of the data collectedwithin a particular climate cycle.5.3.3 Structural ConfigurationThe configuration of the structure should considerthe following:––protection of risers and conductors;––concept for oil storage and export;––wet or dry storage system;––layout of facilities and separationdistances from hazards;––potential for future expansionunder phased development;––potential for platform removal;––environmental constraints;––capability of local constructionfacilities and materials; and––available construction seasonfor offshore operations.conditions, prevailing ice drift directions and icerubble build-up. The topsides should be arrangedwith respect to the functional and operationalrequirements, such as re-supply, offloading,flaring and EER, and with respect to wind and iceencroachment.The reliability of EER, platform supply andoffloading systems can potentially be improvedthrougha) ice management to prevent ice rubbleaccumulation;b) duplication of facilities on opposite sides of theplatform; andc) large crane booms to reach over accumulatedrubble.For stationary floating structures the configurationshall address protection of risers, mooring lines andhull appendages from the surface-level and underhullice interactions. The hull shape should be designedin order to minimize and as much as possible avoiddirect contact between ice and risers, mooring linesand hull appendages for the range of the anticipatedoperating conditions. If ice interactions areunavoidable, the ice actions shall be quantified.5.5 Design ConsiderationsThe combinations of actions and partial factorsfor determining action effects applicable to thedifferent limit states shall be in accordance with theprovisions of Clause 7.Design of stationary floating structures shall accountfor operational measures such as disconnectionor/and ice management. Appropriate interactionsbetween different parts of the structure should beconsidered through the design phases. Ice actions onall relevant structural elements and appurtenancessuch as risers shall be identified and defined fora range of the anticipated operating and designconditions. The weakest element in the system shallbe identified and relevant ice actions shall be studiedin detail.Different structural shapes, orientations andprofiles for the structure and the topsides should beconsidered for resisting sea ice or iceberg actions.In defining the orientation of the structure atthe site, consideration should be given to the iceReport no 2012-0690 67