Offshore Compliant Platforms Analysis, Design, and Experimental Studies

A guide to the analysis and design of compliant offshore structures that highlights a new generation of platforms

Offshore Compliant Platforms provides an authoritative guideto the analysis and design of compliant offshore structures and puts the focus on a new generation of platforms such as: triceratops, Buoyant Leg Storage and Regasification platforms. Whilst the authors – noted experts on the topic – include basic information on the conceptual development of conventional platforms, the book presents detailed descriptions of the design and development of new deep-water platforms.

The book describes the preliminary design of triceratops in ultra-deep waters and presents a detailed analysis of environmental loads that are inherent in offshore locations such as wave, wind and current. The new methodology for the dynamic analysis of triceratops under ice loads, predominantly in ice-covered regions, is also examined with detailed parametric studies. In addition, the book covers the structural geometry and the various methods of analysis for assessing the performance of any other similar offshore platform under the special loads. A discussion of the fatigue analysis and service life prediction is also included. This important book:

•    Includes the analysis and design of compliant offshore structures with a focus on a new generation of platforms

•    Examines the preliminary design of triceratops in ultra-deep waters

•    Covers an analysis of environmental loads that are inherent in offshore locations such as wave, wind and current

•    Reviews the structural geometry and various methods of analysis for assessing the performance of any other similar offshore platform under special loads

•    Discusses fatigue analysis and service life prediction 

Written for engineers and researchers across engineering including civil, mechanical, structural, offshore, ocean and naval architecture, Offshore Compliant Platforms fills the need for a guide to new offshore platforms that provides an understanding of the behaviour of these structures under different loading conditions.

Dr. Srinivasan Chandrasekaran is a Professor in the Department of Ocean Engineering at the Indian Institute of Technology Madras, Tamil Nadu, India.

R. Nagavinothini is a Post-Doctoral Researcher in the Department of Structures for Engineering and Architecture, University of Naples Federico II, Naples, Italy.

List of Figures ix

List of Tables xiii

Foreword by Professor Purnendu K. Das xv

Foreword by Dr. Atmanand N.D. xvii

Series Preface xix

Preface xxi

1 Common Compliant Platforms 1

1.1 Introduction 1

1.2 Tension Leg Platforms 8

1.3 Guyed Tower and Articulated Tower 19

1.4 Floating Structures 21

1.5 Response Control Strategies 24

1.5.1 Active Control Algorithm 25

1.5.2 Semi-Active Control Algorithm 25

1.5.3 Passive Control Algorithm 26

1.5.4 Friction Dampers 27

1.5.5 Metallic Yield Dampers 27

1.5.6 Viscous Fluid Dampers 27

1.5.7 Tuned Liquid Dampers 29

1.5.8 Tuned Liquid Column Damper 30

1.6 Tuned Mass Dampers 31

1.7 Response Control of Offshore Structures 36

1.8 Response Control of TLPs Using TMDs: Experimental Investigations 38

1.9 Articulated Towers 44

1.10 Response Control of ATs: Analytical Studies 48

1.11 Response Control of ATs: Experimental Studies 52

1.11.1 MLAT Without a TMD 53

1.11.2 MLAT with a TMD 56

2 Buoyant Leg Storage and Regasification Platforms 59

2.1 Background Literature 60

2.1.1 Buoyant Leg Structures 62

2.1.2 Floating Production and Processing Platforms 63

2.2 Experimental Setup 64

2.3 Experimental Investigations 65

2.4 Numerical Studies 72

2.5 Critical Observations 76

2.6 Stability Analysis of the BLSRP 85

2.7 Fatigue Analysis of the BLSRP 90

3 New-Generation Platforms: Offshore Triceratops 95

3.1 Introduction 95

3.2 Environmental Loads 96

3.2.1 Regular Waves 96

3.2.2 Random Waves 97

3.2.3 Wind 98

3.2.4 Currents 100

3.3 Fatigue Analysis of Tethers 101

3.4 Response to Regular Waves 104

3.5 Response to Random Waves 108

3.6 Response to Combined Actions of Wind, Waves, and Current 113

3.6.1 Deck Response 116

3.6.2 Buoyant Leg Response 120

3.6.3 Tether Tension Variation 122

3.7 Summary 123

4 Triceratops Under Special Loads 125

4.1 Introduction 125

4.1.1 Ice Load 126

4.1.2 Impact Load Due to Ship Platform Collisions 129

4.1.3 Hydrocarbon Fires 131

4.2 Continuous Ice Crushing 134

4.2.1 The Korzhavin Equation 135

4.2.2 Continuous Ice Crushing Spectrum 136

4.3 Response to Continuous Ice Crushing 138

4.3.1 Response to Ice Loads 139

4.3.1.1 Deck and Buoyant Leg Responses 139

4.3.1.2 Tether Response 140

4.3.2 Effect of Ice Parameters 140

4.3.2.1 Ice Thickness 140

4.3.2.2 Ice Crushing Strength 143

4.3.2.3 Ice Velocity 144

4.3.3 Comparison of Ice- and Wave-Induced Responses 145

4.4 Response to Impact Loads 147

4.4.1 Parametric Studies 151

4.4.1.1 Indenter Size 151

4.4.1.2 Collision Zone Location 152

4.4.1.3 Indenter Shape 153

4.4.1.4 Number of Stringers 154

4.4.2 Impact Response in the Arctic Region 154

4.5 Deck Response to Hydrocarbon Fires 156

4.6 Summary 158

5 Offshore Triceratops: Recent Advanced Applications 161

5.1 Introduction 161

5.2 Wind Turbines 161

5.3 Wind Power 163

5.4 Evolution of Wind Turbines 163

5.5 Conceptual Development of the Triceratops-Based Wind Turbine 164

5.6 Support Systems for Wind Turbines 164

5.6.1 Spar Type 165

5.6.2 TLP Type 165

5.6.3 Pontoon (Barge) Type 165

5.6.4 Semi-Submersible Type 166

5.6.5 Triceratops Type 166

5.7 Wind Turbine on a Triceratops 166

5.8 Response of a Triceratops-Based Wind Turbine to Waves 166

5.8.1 Free-Decay Response 166

5.8.2 Response to Operable and Parked Conditions 169

5.8.3 Effect of Wave Heading Angles 170

5.8.4 PSD Plots 171

5.8.5 Tether Response and Service Life Estimation 172

5.9 Stiffened Triceratops 173

5.9.1 Preliminary Design 173

5.9.2 Response to Wave Action 175

5.9.3 Effect of Wave Direction 177

5.10 Triceratops with Elliptical Buoyant Legs 179

5.10.1 Conceptual Development 180

5.10.2 Response of a Triceratops with Elliptical Buoyant Legs to Wave Action 182

5.11 Summary 186

Model Test Papers 187

References 209

Index 223

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