1、 Guide for Dynamic Loading Approach for Floating Production, Storage and Offloading (FPSO) Installations GUIDE FOR DYNAMIC LOADING APPROACH FOR FLOATING PRODUCTION, STORAGE AND OFFLOADING (FPSO) INSTALLATIONS MAY 2010 (Updated February 2014 see next page) American Bureau of Shipping Incorporated by
2、Act of Legislature of the State of New York 1862 Copyright 2010 American Bureau of Shipping ABS Plaza 16855 Northchase Drive Houston, TX 77060 USA Updates February 2014 consolidation includes: May 2010 version plus Corrigenda/Editorials ABSGUIDE FOR DYNAMIC LOADING APPROACH FOR FPSO INSTALLATIONS .2
3、010 iii Foreword Foreword This Guide provides information about the optional classification notation, Dynamic Loading Approach (DLA), which is available to qualifying ship-type “Floating Production Installations” (FPIs). This type of offshore installation is usually referred to as a “Floating Storag
4、e and Offloading (FSO) System”; or “Floating Production, Storage and Offloading (FPSO) System”, and “FPSO” is the term that will be used herein to denote these ship-type Floating Production Installations. Also, in the text herein, this document is referred to as the “Guide”. Section 1-1-2 of the ABS
5、 Rules for Building and Classing Floating Production Installations (FPI Rules) contains descriptions of the various, basic and optional classification notations available. Part 5A of the FPI Rules gives the specific design and analysis criteria applicable to ship-type FPIs (new build ship-type insta
6、llations and conversions to FPI). In addition to the Rule design criteria, Dynamic Loading Approach based on first-principle direct calculations is acceptable with respect to the determination of design loads and the establishment of strength criteria for ship-type FPIs. In case of any conflict betw
7、een this Guide and the FPI Rules, the latter has precedence. This Guide represents the most current and advanced ABS DLA analysis procedure including linear and nonlinear seakeeping analysis. This Guide is issued May 2010, and is an extended edition of the ABS Guidance Notes on SafeHull-Dynamic Load
8、ing Approach for Floating Production, Storage and Offloading (FPSO) Systems, published in December 2001. Users of this Guide are welcomed to contact ABS with any questions or comments concerning this Guide. Users are advised to check periodically with ABS that this version of this Guide is current.
9、iv ABSGUIDE FOR DYNAMIC LOADING APPROACH FOR FPSO INSTALLATIONS .2010 Table of Contents GUIDE FOR DYNAMIC LOADING APPROACH FOR FLOATING PRODUCTION, STORAGE AND OFFLOADING (FPSO) INSTALLATIONS CONTENTS SECTION 1 Introduction 1 1 Background . 1 3 Concepts and Benefits of DLA Analysis . 1 3.1 Concepts
10、. 1 3.3 Benefits 2 3.5 Load Case Development for DLA Analysis 2 3.7 General Modeling Considerations 3 5 Notations . 4 7 Scope and Overview of the Following Sections 4 FIGURE 1 Schematic Representation of the DLA Analysis Procedure . 6 SECTION 2 Load Cases . 7 1 Basic Considerations 7 3 Vessel Speed
11、7 5 Operational Loading Conditions . 7 7 Dominant Load Parameters 8 7.1 Maximum VBM . 8 7.3 Maximum VSF 9 7.5 Maximum HBM 9 7.7 Maximum HSF . 9 7.9 Maximum Vacc. 9 7.11 Maximum Lacc. 10 7.13 Maximum Roll Angle 10 9 Other Accompanying Instantaneous Load Components 10 11 Mooring Loads 11 13 Impact and
12、 Other Loads . 11 15 Selection of Load Cases . 11 FIGURE 1 Positive Vertical Bending Moment 8 FIGURE 2 Positive Vertical Shear Force 9 FIGURE 3 Positive Horizontal Bending Moment 9 FIGURE 4 Definition of Vessel Motions 10 ABSGUIDE FOR DYNAMIC LOADING APPROACH FOR FPSO INSTALLATIONS .2010 v SECTION 3
13、 Environmental Conditions . 12 1 Basic Considerations 12 3 Wave Spectra . 12 5 Wave Spreading . 14 7 Environmental Data 15 7.1 General 15 7.3 Special Wave Data Needs . 15 7.5 Wave Data for DLA Analysis . 16 FIGURE 1 Definition of Spreading Angles . 15 SECTION 4 Analyses for Vessel Motion, Wave Load,
14、 and Extreme Value 17 1 Overview . 17 3 Still-water Loads . 17 5 Essential Features of Spectral-based Analysis of Motion and Wave Load 18 5.1 General Modeling Considerations . 18 5.3 Diffraction-Radiation Methods . 18 5.5 Panel Model Development 18 5.7 Roll Damping Model 19 5.9 Mooring Line and Rise
15、r Modeling 19 5.11 Vessel Motion and Wave Load Response Amplitude Operators 19 7 Extreme Values for DLA Analysis . 19 FIGURE 1 Panel Model for Diffraction-Radiation Analysis . 18 SECTION 5 Equivalent Design Wave 22 1 General . 22 3 Equivalent Wave Amplitude 22 5 Wave Frequency and Length 22 7 Phase
16、Angle and Wave Crest Position . 23 9 Instantaneous Load Components in a Load Case . 24 11 Nonlinear Pressure Adjustment Near the Waterline . 25 FIGURE 1 Determination of Equivalent Wave Amplitude 23 FIGURE 2 Equivalent Wave Length and Crest Position 23 FIGURE 3 Definition of Wave Heading 24 FIGURE 4
17、 Pressure Adjustment Zones 25 SECTION 6 Nonlinear Vessel Motion and Wave Load 26 1 General . 26 3 Nonlinear Seakeeping Analysis 26 3.1 Concept . 26 3.3 Benefits of Nonlinear Seakeeping Analysis . 26 vi ABSGUIDE FOR DYNAMIC LOADING APPROACH FOR FPSO INSTALLATIONS .2010 5 Modeling Consideration 26 5.1
18、 Mathematical Model . 26 5.3 Numerical Station-keeping Model 27 7 Nonlinear Instantaneous Load Components 27 SECTION 7 External Hydrodynamic Pressure . 28 1 General . 28 3 External Hydrodynamic Pressures Accompanying the Dominant Load Component 28 5 Pressure Loading on the Structural FE Analysis Mod
19、el . 28 FIGURE 1 External Hydrodynamic Pressure Mapping for a Load Case 29 SECTION 8 Internal Liquid Tank Pressure . 30 1 General . 30 3 Pressure Components 30 5 Pressure Head Change due to Roll and Pitch Motions 31 7 Simultaneously Acting Tank Pressure 31 9 Partially Filled Tanks . 31 FIGURE 1 Inte
20、rnal Pressure on a Completely Filled Tank . 32 FIGURE 2 Internal Pressure on a Partially Filled Tank 32 SECTION 9 Local Acceleration and Motion-induced Loads for Lightship Weights and Equipment . 33 1 General . 33 3 Load Components . 33 3.1 Static Load . 33 3.3 Dynamic Load 33 5 Local Acceleration .
21、 34 7 Simultaneously-acting Loads of Lightship Structure and Equipment . 34 SECTION 10 Loading for FEM Global Structural Model 35 1 General . 35 3 Equilibrium Check . 35 5 Boundary Forces and Moments 35 SECTION 11 Structural Analysis of the Hull Structure . 36 1 General . 36 3 Structural Members . 3
22、6 5 3-D Global Analysis Modeling . 37 7 Analyses of Local Structure 37 ABSGUIDE FOR DYNAMIC LOADING APPROACH FOR FPSO INSTALLATIONS .2010 vii SECTION 12 Acceptance Criteria 38 1 General . 38 3 Yielding . 38 3.1 Field Stress . 39 3.3 Local Stress . 39 3.5 Hot-Spot Stress . 39 3.7 Allowable Stresses f
23、or Watertight Boundaries . 39 3.9 Allowable Stresses for Main Supporting Members and Structural Details . 39 5 Buckling and Ultimate Strength 40 TABLE 1 Allowable Stresses for Watertight Boundaries 39 TABLE 2 Allowable Stresses for Various Finite Element Mesh Sizes (Non-tight Structural Members) . 4
24、0 APPENDIX 1 Summary of DLA Analysis Procedure 42 1 General . 42 3 Basic Data Required . 42 5 Hydrostatic Calculations . 42 7 Response Amplitude Operators (RAOs) . 43 9 Extreme Values . 43 11 Equivalent Design Waves . 43 13 Nonlinear Seakeeping Analysis 43 15 External Pressure . 44 17 Internal Liqui
25、d Tank Pressure . 44 19 Loads on Lightship Structure and Equipment . 44 21 Loadings for Structural FE Analysis 44 23 Global FE Analysis 44 25 Local FE Analysis . 45 27 Closing Comments 45 APPENDIX 2 Buckling and Ultimate Strength Criteria 46 1 General . 46 1.1 Approach . 46 1.3 Buckling Control Conc
26、epts 46 3 Plate Panels 46 3.1 Buckling State Limit . 46 3.3 Effective Width 47 3.5 Ultimate Strength . 47 5 Longitudinals and Stiffeners 48 5.1 Beam-Column Buckling State Limits and Ultimate Strength 48 5.3 Torsional-Flexural Buckling State Limit . 49 7 Stiffened Panels 49 7.1 Large Stiffened Panels
27、 between Bulkheads 49 7.3 Uniaxially Stiffened Panels between Transverses and Girders . 49 viii ABSGUIDE FOR DYNAMIC LOADING APPROACH FOR FPSO INSTALLATIONS .2010 9 Deep Girders and Webs . 50 9.1 Buckling Criteria. 50 11 Corrugated Bulkheads 50 11.1 Local Plate Panels . 50 11.3 Unit Corrugation. 51
28、11.5 Overall Buckling . 51 APPENDIX 3 Nominal Design Corrosion Values (NDCV) for FPSOs 52 1 General . 52 3 Nominal Design Corrosion Values 52 3.1 Double Hull Ship-type Installations 52 3.3 Single Hull and Double Side Single Bottom Ship-type Installations 53 TABLE 1 Nominal Design Corrosion Values 53
29、 FIGURE 1 Nominal Design Corrosion Values 52 ABSGUIDE FOR DYNAMIC LOADING APPROACH FOR FPSO INSTALLATIONS .2010 1 Section 1: Introduction SECTION 1 Introduction 1 Background The design and construction of the hull, superstructure, and deckhouses of a ship-type FPI that can be a new build or conversi
30、on are to be based on all applicable requirements of the ABS Rules for Building and Classing Floating Production Installations (FPI Rules). The design criteria for these structures, as given in the FPI Rules, reflect the structural performance and demands expected of a floating production installati
31、on which is moored at a particular site on a long-term basis. The design criteria for a ship-type installation are located in Part 5A, Chapters 1 through 4 of the FPI Rules. Part 5A, Chapters 1, 2, and 3 are applicable to vessels of 150 meters (492 feet) or more in length, while Part 5A, Chapter 4,
32、applies to vessels under 150 meters (492 feet) in length. The FPI criteria contained in Part 5A of the FPI Rules entail a two-step procedure. The first step, referred to as the Initial Scantling Evaluation (ISE), is scantling selection to accommodate global and local strength requirements. The scant
33、ling selection is accomplished through the application of design equations that reflect combinations of: probable extreme, dynamically induced loads; durability considerations; expected service, survey and maintenance practices; and structural strength considering the failure modes of material yield
34、ing and buckling. Also, a part of ISE is an assessment of fatigue strength primarily aimed at connections between longitudinal stiffeners and transverse web frames in the hull structure. The second step of the FPI criteria, referred to as the Total Strength Assessment (TSA), requires the performance
35、 of finite structural analysis using either a three cargo tank length model or cargo block length model, to validate the selected scantlings from the initial ISE phase. The main purpose of the TSA analysis is to confirm that the selected design scantlings are adequate (from a broader structural syst
36、em point of view) to resist the failure modes of yielding, buckling and ultimate strength, and fatigue. The Dynamic Loading Approach (DLA) provides an enhanced structural analysis basis to assess the capabilities and sufficiency of a structural design. A fundamental requirement of DLA is that the ba
37、sic, initial design of the structure is to be in accordance with the Rule criteria as specified in the FPI Rules. The results of the DLA Analyses cannot be used to reduce the basic scantlings obtained from the direct application of the Rule criteria scantling equations. However, should the DLA Analy
38、sis indicate the need to increase any basic scantling this increase is to be accomplished to meet the DLA criteria. This Guide is applicable to ship-type installations of all size and proportions including new build ship-type FPI and conversions to FPI. 3 Concepts and Benefits of DLA Analysis 3.1 Co
39、ncepts The structural design portions of the FPI Rules (i.e., see especially Part 5A, Chapter 3) are intended to provide an appropriate and sufficient basis for the design and analysis of the hull structure of an FPSO. This was done by modifying tanker structural design criteria to reflect site-spec
40、ific environmental loadings and other design features of an FPSO. The other design features include such items as possible turret based mooring, deck-mounted hydrocarbon processing equipment, etc. The FPI Rules includes provisions that address these matters with emphasis on the sequence, process and
41、 objectives of design, not on the structural analysis itself. Section 1 Introduction 2 ABSGUIDE FOR DYNAMIC LOADING APPROACH FOR FPSO INSTALLATIONS .2010 DLA is an analysis process, rather than the step-wise design oriented process that FPI Rules criteria is. The DLA analysis emphasizes the complete
42、ness and realism of the analysis model in terms of both the extent of the structure modeled and the loading conditions analyzed. In a manner that is the converse of the FPI Rules criteria, in DLA the modeling and analysis process relies on performing multiple levels of analysis that start with an ov
43、erall or global hull model, and the results of each previous level of analysis are used to establish areas of the structure requiring finer (more detailed) modeling and analysis, the local loading to be re-imposed and the boundary conditions to be imposed on the finer model. The Load Cases considere
44、d in the DLA analysis possess the following attributes: i) Use of tank-loading patterns, other loading components, and vessel operating drafts that reflect the actual ones intended for the vessel (note that the Load Cases in the FPI Rules criteria comprise mainly those intended to produce scantling
45、design controlling situations). ii) Load components are combined to assemble each DLA Load Case. The dynamic related aspects of the components are incorporated in the model, and the combination of these dynamically considered components is accommodated in the analysis method. iii) The use of environ
46、mental and other load effects for the installation site directly considers the functional role of the FPI as a site-dependent structure, using design return periods appropriate to this function. Also, the phasing and relative directionality that exist between environmental effects and the structure
47、itself can be directly considered. iv) Because of the required extent of the structural modeling, the direct effects and the interaction between structural subsystems (such as mooring turret and main deck supported equipment modules) can be directly assessed. 3.3 Benefits The enhanced realism provid
48、ed by the DLA analysis gives benefits that are of added value to the Operator/Owner. The most important of these is an enhanced and more precise quantification of structural safety based on the attributes mentioned above. Additionally, the more specific knowledge of expected structural behavior and
49、performance is very useful in more realistically evaluating and developing inspection and maintenance plans. The usefulness of such analytical results when discussing the need to provide possible future steel renewals should be apparent. An under-appreciated, but potentially valuable benefit that can arise from the DLA Analysis is that it provides access to a comprehensive and authoritative structural evaluation model, which may be readily employed in the event of emergency situations that might occur during the service life of the FPI, such as structur
