Book contents
- Frontmatter
- Contents
- Preface
- Acknowledgments
- How to Use This Book
- 1 Overview of Ship-Shaped Offshore Installations
- 2 Front-End Engineering
- 3 Design Principles, Criteria, and Regulations
- 4 Environmental Phenomena and Application to Design
- 5 Serviceability Limit-State Design
- 6 Ultimate Limit-State Design
- 7 Fatigue Limit-State Design
- 8 Accidental Limit-State Design
- 9 Topsides, Mooring, and Export Facilities Design
- 10 Corrosion Assessment and Management
- 11 Inspection and Maintenance
- 12 Tanker Conversion and Decommissioning
- 13 Risk Assessment and Management
- Appendix 1 Terms and Definitions
- Appendix 2 Scale Definitions of Winds, Waves, and Swells
- Appendix 3 Probability of Sea States at Various Ocean Regions
- Appendix 4 Scaling Laws for Physical Model Testing
- Appendix 5 Wind-Tunnel Test Requirements
- Appendix 6 List of Selected Industry Standards
- Index
- References
7 - Fatigue Limit-State Design
Published online by Cambridge University Press: 17 September 2009
- Frontmatter
- Contents
- Preface
- Acknowledgments
- How to Use This Book
- 1 Overview of Ship-Shaped Offshore Installations
- 2 Front-End Engineering
- 3 Design Principles, Criteria, and Regulations
- 4 Environmental Phenomena and Application to Design
- 5 Serviceability Limit-State Design
- 6 Ultimate Limit-State Design
- 7 Fatigue Limit-State Design
- 8 Accidental Limit-State Design
- 9 Topsides, Mooring, and Export Facilities Design
- 10 Corrosion Assessment and Management
- 11 Inspection and Maintenance
- 12 Tanker Conversion and Decommissioning
- 13 Risk Assessment and Management
- Appendix 1 Terms and Definitions
- Appendix 2 Scale Definitions of Winds, Waves, and Swells
- Appendix 3 Probability of Sea States at Various Ocean Regions
- Appendix 4 Scaling Laws for Physical Model Testing
- Appendix 5 Wind-Tunnel Test Requirements
- Appendix 6 List of Selected Industry Standards
- Index
- References
Summary
Introduction
As we discussed in Chapters 3 and 5, limit states are classified into four categories: serviceability limit states (SLS), ultimate limit states (ULS), fatigue limit states (FLS), and accidental limit states (ALS). This chapter presents FLS design principles and criteria together with selected engineering practices applicable for the structure of ship-shaped offshore units.
Under the action of repeated loading, fatigue cracks may in time be initiated in the stress concentration areas of ship-shaped offshore structures, and indeed have been reported by Hoogeland et al. (2003) and Newport et al. (2004), among others. In general, the fatigue damage at a crack initiation site is affected by many factors, such as material properties (e.g., elastic modulus, ultimate tensile stress); high local stresses (e.g., stress concentration, residual stresses); size of components; nature of stress variation (e.g., stress variation during the loading and off-take cycles, number of wave-induced stress range cycles); and environmental and operational factors including corrosion and performance of coatings. Potential flaws (e.g., poor materials, porosity, slag inclusions, undercuts, lack of fusion, incomplete weld root penetration) and misalignments can also significantly increase stress concentration and initial defects at welds.
To achieve greater fatigue durability in a structure, therefore, stress concentrations, flaws, and structural degradation, including corrosion and fatigue effects, must either be avoided or minimized or, more commonly, their levels and effects either in design, construction, and/or service must be monitored and effectively controlled to acceptable levels.
- Type
- Chapter
- Information
- Ship-Shaped Offshore InstallationsDesign, Building, and Operation, pp. 217 - 256Publisher: Cambridge University PressPrint publication year: 2007