Final report for WP4.3: Enhancement of design methods ... - Upwind

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UPWIND WP4: Offshore Support Structures and Foundations Applicability for FOWT: • Detailed requirements for design calculations. Description of load cases which cover design situations and external conditions. Applicable for FOWT too. Extension to further specific requirements for FOWT is needed. • Restrictions: specific requirements for FOWT (e.g. floating units, mooring) mainly as reference to Offshore Rules. BV Guidance Note NI 572 DT R400 E, November 2010 – Classification and Certification of Floating Offshore Wind Turbines Scope: • This guidance notes gives requirements and recommendations for the classification of Floating Offshore Wind Turbines. Applicability for FOWT: • The load cases adopted for the design are defined on basis of the minimum load cases required by IEC 61400-3 or load combinations of Offshore Rules. ISO 19904-1 - Petroleum and natural gas industries - Floating offshore structures - Part 1: Monohulls, semi submersibles and spars Scope: • Requirements and guidance for the structural design and/or assessment of floating offshore platforms used by the petroleum and natural gas industries. Reference to DNV-OS-C101. Applicability for FOWT: • General requirements for floating offshore platforms • Restrictions: No specific wind turbine design load case requirements ISO 19901-7 – Petroleum and natural gas Industries – Specific requirements for offshore structures – Part 7: Stationkeeping systems for floating offshore structures and mobile offshore units, 2005 Scope: • This part of ISO 19901 specifies methodologies for the design, analysis and evaluation of stationkeeping for floating structures used by the oil & gas industries Applicability for FOWT: • General requirements for floating offshore structures • Restrictions: No specific wind turbines design load case requirements DNV-OS-C101 - Design of Offshore Steel Structures, General (LRFD method) Scope: • Provides design principles, technical requirements and guidance for the structural design of offshore structures. DNV-OS-C101 is the general part of the DNV offshore rules for structures. Applicability for FOWT: • General requirements for all offshore structures • Restrictions: No specific wind turbine design load case requirements DNV-OS-E301 - Position Mooring Scope: • Applicable to all types of floating offshore units including buoys Applicability for FOWT: • Specific guideline for mooring systems, e.g. applicable for FOWT • Restrictions: n/a API RP 2SK - Design and Analysis of Station keeping Systems for Floating Structures Scope: • Purpose is to present a rational method for analyzing, designing or evaluating station-keeping systems used for floating units. Applicability for FOWT: • Recommended practice with detailed guidance for moorings systems including design, analysis and operation. • Restrictions: n/a 132
UPWIND WP4: Offshore Support Structures and Foundations Other standards API RP 2A-LRFD - Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms - Load and Resistance Factor Design API RP 2A-WSD - Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms - Working Stress Design API RP 2T - Recommended Practice for Planning, Designing and Constructing for Tension Leg Platforms DNV-OSS-312 - Certification of Tidal and Wave Energy Converters DNV-OS-C201 - Structural Design of Offshore Units (WSD method) DNV-OS-C401 - Fabrication and Testing of Offshore Structures ISO 19900 - Petroleum and Natural Gas Industries – General Requirements for Offshore Structures ISO 19900-1 - Petroleum and natural gas industries - Specific requirements for offshore structures - Part 1: Metocean design and operating considerations ISO 19902 - Petroleum and Natural Gas Industries – Fixed Steel Offshore Structures 9.2 Extensions to IEC 61400-3 standard for floating structures The IEC 61400-3 standard specifies essential design requirements to ensure the engineering integrity of offshore wind turbines, in order to provide an appropriate level of protection against damage during the planned lifetime. The current edition of the standard is applicable to bottom-mounted offshore wind turbines only, and it is stated explicitly in the standard that the design requirements specified are not sufficient to ensure the engineering integrity of floating offshore wind turbines. There are a number of design advantages to floating support structures for offshore wind turbines. The principal advantage is that floating support structures enable the use of deep water sites, which hugely increases the number of potential locations for offshore wind farms. There is also a decrease in the dependence of support structure design on site conditions, and therefore more opportunity for production at large scales. As suitable shallow water sites are used up it is expected that designers will increasingly investigate deep water sites which would require floating support structures. The projected increase in demand for floating wind turbines requires a corresponding development of the design standards and requirements, in order to ensure the engineering integrity of floating wind turbines. Recommendations are presented for possible extensions to the IEC 61400-3 standard to enable applicability to deep-water floating wind turbine designs, including the implementation of additional/different design load cases. Issues that need to be considered when defining DLCs for FOWTs include the following: 1. Potential large motions of the rotor-nacelle assembly. Influence of heave motion on air gap and rotor clearance needs to be revised. For the majority of offshore wind turbines installed to date, the wind conditions have been the primary external consideration in the assessment of the structural integrity of the rotor-nacelle assembly (RNA) and marine conditions have been of much less importance. However, for floating wind turbines the dynamic properties of the support structure mean that the marine conditions will have a much greater influence on the RNA loads. The IEC 61400-3 standard currently states that the RNA may be designed to generic wind conditions, but that structural integrity of the RNA must be demonstrated by taking proper account of the marine conditions at each specific site where the offshore wind turbine will be subse- 133
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Project UpWind Contract No.: 019945
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Acknowledgement The presented work
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Summary The overall aim of the UpWi
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Table of Contents Acknowledgement..
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Task 4.1 Integration of support str
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Sequential coupling The sequential
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analysis. In the new multibody code
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Figure 2.4: 2nd global bending mode
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3.2 Comparison of deterministic loa
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Figure 3.5: Time series of axial fo
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• Time domain simulation in ADCoS
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• A supplementary load vector for
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The following results are found: Fi
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Figure 4.5: Output positions in the
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It is directly visible that there i
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ated eigenfrequency is shifted into
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Water levels For the calculation of
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guidelines for the inclusion of cli
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damaging if the frequency of the ex
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uncertain parameters carefully. Thr
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Table 5.3 shows annual reliability
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Steel substructure for offshore win
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Table 5.16 shows the required FDF v
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A Fracture Mechanical (FM) modellin
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Figure 5.4: Annual reliability indi
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Further, the effect of possible ins
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Rainflow evaluation The load cases
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For DLC 7.2 it has to be considered
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Guideline, DLC 1.5). Furthermore, t
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Table 5.28: Output locations for da
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From these results it can be clearl
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Figure 5.11: Normalised DELs with v
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Figure 5.14 presents normalized DEL
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Figure 5.16: Output locations for e
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UPWIND WP4: Offshore Support Struct
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Final report for WP4.3: Enhancement of design methods ... - Upwind

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