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Barents 2020 Working Group 2

Barents 2020 Working Group 2. Barents 2020 Conference Meeting Moscow December 8, 2010. Working Group RN02 – Guidance to ISO 19906 for design of stationary floating installations against ice-loads. Deliverables:

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Barents 2020 Working Group 2

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  1. Barents 2020 Working Group 2 Barents 2020 Conference Meeting Moscow December 8, 2010

  2. Working Group RN02 – Guidance to ISO 19906 for design of stationary floating installations against ice-loads Deliverables: • Agreed Guidance Document for design against ice loads on stationary floating structures that may serve as a common Russian-Norwegian separate supplement to ISO 19906 for the Barents Sea. The Guidance Document that may be submitted, partly or in full, to ISO for their consideration in connection with the first update of ISO19906.

  3. Barents 2020 Phase 4 – Working Group 2 Members

  4. RN02 - Status • In-depth review and gap analysis by SDAG andStatoil, comments to more than 75 sub-clauses • Voluntary contributions from participants; assigned tasks for topics • Revised work plan • Rough layout of final report

  5. Review of ISO 19906; example, one out of 16 pages

  6. Review of ISO 19906; example, one out of 16 pages

  7. Contribution list; one half out of four pages

  8. Some issues • Ice Management (IM) and impact on floater design • Can IM be used to reduce design loads? If yes, how and what are requirements to documentation? • Ice model testing, floaters • Details missing • Ice data • How to handle sparse data statistically?

  9. System reliability Taking into account the reliability of compontents in IM system Structure reliability IM efficiency Ice Management (IM) and impact on floater designSafety level and system reliability • Barents 2020 objective is to achieve similar safety level as in the North Sea • System reliability is a function of the component reliability of the structure and the efficiency of the components in the Ice Management (IM) system

  10. Ice Management (IM) and impact on floater designDesign, ice management and disconnection • “Any ice management approach that is intended to support the operation of an offshore system (floating, fixed, subsea or otherwise) shall be configured to achieve an acceptable level of overall system reliability, in combination with structural resistance. The acceptable level of system reliability should be determined according to the principles set out in Clause 7 over the design service life of the system(s) the ice management system is supporting.” IM philosophy Reflect overall system reliability Design philosophy Disconnection philosophy

  11. Ice Management (IM) and impact on floater designManaged ice • Gap analysis: • Reduction of design ice actions resulting from design ice features (i.e EL or AL level) is not obvious. No guidance on methodology is offered. • Adverse effect should be identified • Contributions: • Documentation of reduction of design ice actions resulting from design ice features (i.e EL or AL level) in case of IM. • Quantification of the effect of ice management as well as the impact of the chosen design philosophy on the overall design • Summarize general findings and learnings from managed ice to be determined from full-scale experience from Kulluk. • Assess adverse effects arising from Ice Management (ISO requirement). A list of so-called ‘adverse effects’ to be be provided

  12. Ice model testing of floaters • Gap: • No particular guidance offered for testing of floating systems in ice tanks. • Details missing • Contributions: • Performance requirements for model testing of floaters to be provided • Assessment of deviations between two modelling approaches: • towing or pushing the model through a stationary ice sheet; • pushing the ice sheet towards the stationary model; • Note that ice model test results should be corrected according to actual obtained ice characteristics in order to make them comparable to full scale

  13. Ice model testing of floaters (2) • Contibutions: • Outline of special requirements to mooring system; • Moored system stiffness to be quantified in model scale and compared to prototype design; • Pull-out tests should be performed to assess the model scale mooring system; • Decay tests should be performed for deriving the natural periods of the model in open water; • Note on assessment of ice-structure friction coefficient to be assessed in model scale; • Note on importance of logging structure motions and accelerations, i.e. degrees of freedom, for various structure types • Notice on determination of rubble parameters for ice ridge characteristics in model tests, such as rubble strength and density

  14. Ice data • Identifed gaps: • Estimating statistical distributions for sea ice and icebergs based on fairly limited databases should be addressed. • How to handle limited data sets in general. Consider distributions for probabalistic calculations or define parameters or, when no data, recommend on parameters • Contributions will include improved guidance on • Considerations on data requirements • Characterization of ice drift • Defining ice properties that can not be readily measured in the field • Definition on ice concentration • Ice berg shape coefficients, iceberg adverse shapes and iceberg stability • Expert judgement on physical and mechanical properties of ice

  15. Ice data – contributions continued • Additional guidance on handling of limited data sets. Objective shall be to define distributions (with focus on tails and cut-offs) for probabilistic load calculations and not least define deterministic parameters for deterministic load calculation checks (in particular for AL). Where no data is available, recommendations shall be provided on which parameters to use. • Additional guidance to be provided on i) interpretation of satellite data; ii) variability of ice drift; iii) geophysical scale ice pressure

  16. Layout of final report - proposal • Introduction • Brief Barents 2020 description and history • Description of work process • Gap analysis • Background information/justification for recommendations • For each recommended supporting text, a brief descripription on the basis/background • Recommendations on supplementary text • Organized according to clauses in ISO 19906 where we suggest supporting text • Recommendations, other

  17. Proposed Work Plan 2011 Early March : Text proposals received by DNV 3rd week March: Draft text for guidelines from editing group/DNV End March: 3rd group meeting, review texts, sort out issues; workshop May 13: Draft report from DNV, including draft text for guidelines End May: 4th group meeting, review texts, sort out issues, detailed plan for fall End June: Revised texts from editing group/DNV End August: Comments to latest revision Mid September: Texts 90-95% complete, editing group/DNV End September: Discuss additional changes Mid October: Distribution of revised texts, editing group/DNV Early November: Comments to last version Mid November: Final texts distributed, only cosmetics left December: Last group meeting, cosmetic changes, preparation of presentations to Steering Committee and Plenary 17

  18. Thank you for the attention Safeguarding life, property and the environment www.dnv.com

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