U

iARINE TRUCTURAL DESIGNLVLoads Ultimate strength, Fatigue and frature Structural reliability, Risk assessment

Functional requirements

I

I

I

ILimit-state design

R(ftJym,...,) > S(Y,Q,)

ELSEVIER

MARINE STRUCTURAL DESIGN

Elsevier Internet Homepage: http:Nwww.elsevier.com Consult the Elsevier homepage for full catalogue information on all books, journals and electronic products and services.

Elsevier Titles of Related Interest Ocean Engineering SeriesWATSON Practical Ship DesignISBN 008-042999-8

OWENS Steel in Construction (CD-ROM Proceedings with Printed Abstracts Volume, 268 papers)ISBN 008-042997-1

YOUNG Wind Generated Ocean WavesISBN: 008-043317-0

GODOY Thin-Walled Structureswith Structural Imperfections: Analysis and BehaviorISBN: 008-042266-7

BAl Pipelinesand RisersISBN 008-043712-5

FUKUMOTO StructuralStability DesignISBN: 008-042263-2

JENSEN

Local and Global Response of ShipsISBN: 0080439S3-S

GUEDES-SOARES Advances in Safety and Reliability (3 Volume Set)ISBN: 008-04283s-S

TUCKER & PITT Waves in Ocean EngineeringISBN 008-043566-1

CHAN & TENG ICASS '02. Advances in Steel Structures (2 Volume Set)ISBN. 008-044017-7

Other Titles

MOAN & BERGE13&Int Ship & Offshore StructuresCongress (ISSC 1997) ISBN: 008-042829-0

OHTSUBO & SUM1 14' Int. Ship and OffshoreStructures Congress (ISSC 2000)ISBN: 008-043602-1

Related Journals Free specimen copy gladly sent on request. Elsevier Lid, The Boulevard, Langford Lane, Kidlington, Oxford, OX5 IGB, UKApplied Ocean Research Advances in Engineering Software CAD Coastal Engineering Composite Strua~res Computers and Structures Construction and Building Materials Engineering Failure Analysis Engineering Fracture Mechanics Engineering Structures Finite Elements in Analysis and Design International Journal of Solids and Structures Journal of Constructional Steel Research Marine Structures NDT & E International Ocean Engineering Structural Safety Thin-Walled Structures

To Contaet the PublisherElsevier welcomes enquiries concerning publishing proposals: books,journal special issues, conference proceedings, etc. All formats and media can be considered. Should you have a publishing proposal you wish to discuss, please contact, without obligation, the publisher responsible for Elsevier's civil and strucutral engineering publishing programme: James Sullivan Publishing Editor Elsevier Ltd The Boulevard, Langford Lane Kidlington, Oxford OX5 IGB, UK

Phone: Fax: E.mail:

-4-441865 843178 +44 I865 843920j.sullivan@elsevier.com

General enquiries, including placing orders, should be directed to Elsevier's Regional Sales Offices - please access the Elsevier homepage for full contact details (homepage details at the top of this page).

MARINE STRUCTURAL DESIGN

YONG BAI

2003 ELSEVIER

Amsterdam - Boston - Heidelberg - London - New York - Oxford Paris - San Diego - San Francisco - Singapore - Sydney - Tokyo

ELSEVIER SClENCE Ltd The Boulevard, Langford Lane Kidlington, Oxford OX5 IGB, UK8 2003 Dr. Yong Bai. All rights reserved

This work is protected under copyright of Dr. Yong Bai with assigned rights to Elsevier Science. The following terms and conditions apply to its use: Photocopying Single photocopies of single chapters may be made for personal use as allowed by national copMght laws. Permission of the Publisher and payment of a fee is required for all other photocopying, including multiple or systematic copying, copying for advertising or promotional purposes, resale, and all forms of document delivery. Special rates are available for educational institutions that wish to make photocopies for non-profit educational classroom use. Permissions may be sought directly from Elseviers Science & Technology Rights Department in Oxford, U K phone: (+44)1865 843830, fax: (+44) 1865 853333, e-mail: pennissions@elsevier.com. You may also complete your request on-line via the Elsevier Science homepage (http:Nwww.elsevier.com), by selecting Customer Support and then Obtaining Permissions. In the USA, users may clear permissions and make payments through the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA, phone: (+I) (978) 7508400, fax: (+I) (978) 7504744, and in the UK through the Copyright Licensing Agency Rapid Clearance Service (CLARCS), 90 Tottenham Court Road, London W1P OLP, UK, phone: (4) 631 5555; fax: (+44) 207 631 5500. Other countries may have a local 207 reprographic rights agency for payments. Derivative Works Tables of contents may be reproduced for internal circulation, but permission of Elsevier Science is required for external resale or distribution of such material. Permission of the Publisher is required for all other derivative works, including compilations and translations. Electronic Storage or Usage Permission of the Publisher is required to store or use electronically any material contained in this work, including any chapter or part of a chapter. Except as outlined above, no part of this work may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electmnic, mechanical, photocopying, recording or otherwise, without prior written permission of the Publisher. Address permissions requests to: Elseviers Science & Technology Rights Department, at the phone, fax and email addresses noted above. Notice No responsibility is assumed by the Publisher for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the material herein. Because of rapid advances in the medical sciences, in particular, independent verification of diagnoses and drug dosages should be made. First edition 2003 Library of Congress Cataloging in Publication Data A catalog record from the Library of Congress has been applied for. British Library Cataloguing in Publication Data Bai, Yong Marine Structural Design 1. Offshore structures - Design and construction 2. Marine engineering 1. Title 627.98 ISBN: 0-08-043921-7

8 The paper used in this publication meets the requirements of ANSVNISO 239.48-1992 (Permanence of Paper).Printed in Hungary.

PREFACEThis book is written for marine structural engineers and naval architects, as well as mechanical engineers and civil engineers who work on struch~raldesign. The preparation of the book is motivated by extensive use of the finite element analysis and dynamidfatigue analysis, fast paced advances in computer and information technology, and application of risk and reliability methods. As the professor of offshore structures at Stavanger University College, I developed this book for my teaching course TE 6076 Offshore Structures and TE6541 Risk and Reliability Analysis of Offshore Structures for M.Sc and Ph.D. students. This book has also been used in IBC/Clarion industry training courses on design and construction of floating production systems for engineers in the oil/@ industry.As reliability-based limit-state design becomes popular in structural engineering, this book may also be a reference for structural engineers in other disciplines, such as buildings, bridges and spacecraft.

My former supervisors should be thanked for their guidance and inspiration. These include: Executive Vice President Dr. Donald Liu at American Bureau of Shipping (ABS), Professor Torgeir Moan at Norwegian University of Science and Technology 0, Professor Robert Bea and Professor Alaa Mansour at University of California at Berkeley, Prof. Preben Terndrup Pedersen at Technical University of Denmark, Professor T. Yao at Osaka University and Professor M. Fujikubo at Hiroshima University. The friendship and technical advice from these great scientists and engineers have been very important for me to develop materials used in this book.As manager of advanced engineering department at JP Kenny Norway office (now a section of ABB)

and manager of offshore technology department at the American Bureau of Shipping, I was given opportunities to meet many industry leaders in oil companies, desigdconsulting offices, classification societies and contractors. From ISSC, IBC, S N M , OMAE, ISOPE and OTC conferences and industry (ISO/APYDeepstar) committees, I leamed about the recent developments in industry applications and research.

r The collaboration with Dr. R u i n Song and D .Tao Xu for a long period of time has been helpful to develop research activities on structural reliability and fatigue respectively. Sections of this book relating to extreme response, buckling of tubular members, FPSO hull girder strength and reliability and ISOPE papers co-authored with Professors Preben Temdrup were based on my SNAME, 0 Pedersen and T. Yao and Drs. Yung Shin, C.T. Zhao and H.H. Sun.Dr. Qiang Bai and Ph.D. student Gang Dong provided assistance to format the manuscript. Professor Rameswar Bhattacharyya, Elseviers Publishing Editor James Sullivan and Publisher Nick Pinfield and Senior Vice President James Card of ABS provided me continued encouragement in completing this book.

I appreciate my wife H a Peng and children, Lihua and Carl, for creating an environment in which it u has been possible to continue to write this book for more than 5 years in different culture and working environments.I wish to thank all of the organizations and individuals mentioned in the above (and many friends and authors who were not mentioned) for their support and encouragement.

Yong BAI Houston, USA

TABLE OF CONTENTS

Preface................................................................................................................................................

v

Part I: Structural Design Principles CHAPTER 1 INTRODUCTION.........................................................................................................1.1 Structural Design Principles ........................................................................................................ 1.1.1 Introduction.......................................................................................................................... 1.1.2 Limit-State Design ............................................................................................................... 1.2 Strength and Fatigue Analysis..................................................................................................... 1.2.1 Ultimate Strength Criteria.................................................................................................... 1.2.2 Design for Accidental Loads................................................................................................ 1.2.3 Design for Fatigue................................................................................................................ 1.3 Structural Reliability Applications............................................................................................ 1.3.1 Structural Reliability Concepts .......................................................................................... 1.3.2 Reliability-Based Calibration of Design Factor ................................................................. 1.3.3 Requalification of Existing Structures.............................................................................. 1.4 Risk Assessment........................................................................................................................ 1.4.1 Application of Risk Assessment ........................................................................................ 1.4.2 Risk-Based Inspection (RBI) ............................................................................................. 1.4.3 Human and Organization Factors....................................................................................... 1.5 Layout of This Book .................................................................................................................. 1.6 How to Use This Book .............................................................................................................. 1.7 References ................................................................................................................................. CHAPTER 2 WAVE LOADS FOR SHIP DESIGN AND CLASSIFICATION

3 3 3 45

6 7 8 10 10 12 12 13 13 13 14 14 1616

.............

19 19 19 19 21 22 24 26 26 26 28 29 30 32 32 33 35 39

2.1 Introduction ............................................................................................................................... 2.2 Ocean Waves and Wave Statistics............................................................................................. 2.2.1 Basic Elements of Probability and Random Process.......................................................... 2.2.2 StatisticalRepresentation of the Sea Surface..................................................................... 2.2.3 Ocean Wave Spectra .......................................................................................................... 2.2.4 Moments of Spectral Density Function.............................................................................. 2.2.5 StatisticalDetermination of Wave Heights and Periods .................................................... 2.3 Ship Response to a Random Sea ............................................................................................... 2.3.1 Introduction........................................................................................................................ 2.3.2 Wave-Induced Forces......................................................................................................... 2.3.3 Structural Response............................................................................................................ 2.3.4 Slamming and Green Water on Deck................................................................................. 2.4 Ship Design for Classification................................................................................................... 2.4.1 Design Value of Ship Response......................................................................................... 2.4.2 Design Loads per Classification Rules............................................................................... 2.5 References ................................................................................................................................. CHAPTER 3 LOADS AND DYNAMIC RESPONSE FOR OFFSHORE STRUCTURES 3.1 General.......................................................................................................................................

........39

viii

Contents

3.2 Environmental Conditions......................................................................................................... 3.2.1 Environmental Criteria....................................................................................................... 3.2.2 Regular Waves ................................................................................................................... 3.2.3 Irregular Waves .................................................................................................................. 3.2.4 Wave Scatter Diagram ....................................................................................................... 3.3 Environmental Loads and Floating Structure Dynamics........................................................... 3.3.1 Environmental Loads ......................................................................................................... 3.3.2 Sea loads on Slender Structures......................................................................................... 3.3.3 Sea loads on Large-Volume Structures.............................................................................. 3.3.4 Floating Structure Dynamics .............................................................................................. 3.4 Structural Response Analysis .................................................................................................... 3.4.1 Structural Analysis ............................................................................................................. 3.4.2 Response Amplitude Operator (RAO)............................................................................... 3.5 Extreme Values.......................................................................................................................... 3.5.1 General ............................................................................................................................... 3.5.2 Short-Term Extreme Approach.......................................................................................... 3.5.3 Long-Term Extreme Approach.......................................................................................... ..... 3.5.4 Prediction of Most Probable Maximum Extreme for Non-Gaussian Process. . . . . 3.6 Concluding Remarks ................................................................................................................. 3.7 References ................................................................................................................................. 3.8 Appendix A Elastic Vibrations of Beams................................................................................. 3.8.1 Vibration of A Springhiass System .................................................................................. 3.8.2 Elastic Vibration of Beams ................................................................................................

39 39 41 41 42 45 45 45 45 46 47 47 49 53 53 54 58 61 65 66 68 68 69

CHAPTER 4 SCANTLING OF SHIP'S HULLS BY RULES

............................

7171 71 71 73 75 76 76 77 79 79 79 79 79 82 83 83 85 87

4.1 General....................................................................................................................................... 4.2 Basic Concepts of Stability and Strength of Ships.................................................................... 4.2.1 Stability.............................................................................................................................. 4.2.2 Strength.............................................................................................................................. 4.2.3 Corrosion Allowance ......................................................................................................... 4.3 Initial Scantling Criteria for Longitudinal Strength................................................................... 4.3.1 Introduction........................................................................................................................ 4.3.2 Hull Girder Strength........................................................................................................... 4.4 Initial Scantling Criteria for Transverse Strength...................................................................... 4.4.1 Introduction........................................................................................................................ 4.4.2 Transverse Strength............................................................................................................ 4.5 Initial Scantling Criteria for Local Strength .............................................................................. 4.5.1 Local Bending of Beams.................................................................................................... 4.5.2 Local Bending Strength of Plates....................................................................................... 4.5.3 Structure Design of Bulkheads, Decks, and Bottom.......................................................... 4.5.4 Buckling of Platings........................................................................................................... 4.5.5 Buckling of Profiles ........................................................................................................... 4.6 References .................................................................................................................................

CHAPTER 5 SHIP HULL SCANTLING DESIGN BY ANALYSIS

............................................

8989 89 91 91 93 94 94 95

5.1 General....................................................................................................................................... 5.2 Design Loads ............................................................................................................................. 5.3 Strength Analysis using Finite Element Methods...................................................................... 5.3.1 Modeling ............................................................................................................................ 5.3.2 Boundary Conditions ......................................................................................................... 5.3.3 Type of Elements ............................................................................................................... 5.3.4 Post-Processing.................................................................................................................. 5.4 Fatigue Damage Evaluation.......................................................................................................

Contents5.5 6. I

ir97

References .................................................................................................................................

CHAPTER 6 OFFSHORE STRUCTURALANALYSIS

...............................................................

9999 99 99

6.1 .1 General ............................................................................................................................... 6.1.2 Design Codes ..................................................................................................................... 6.1.3 Government Requirements............................................................................................... 6.1.4 CertificatiodClassificationAuthorities............................................................................ 6.1.5 Codes and Standards........................................................................................................ 6.1.6 Other Technical Documents............................................................................................. 6.2 Project Planning....................................................................................................................... 6.2.1 General ............................................................................................................................. 6.2.2 Design Basis ..................................................................................................................... 6.2.3 Design Brief ..................................................................................................................... 6.3 Use of Finite Element Analysis ............................................................................................... 6.3.1 Introduction...................................................................................................................... 6.3.2 Stiffness Matrix for 2D Beam Elements .......................................................................... 6.3.3 Stifmess Matrix for 3D Beam Elements .......................................................................... 6.4 Design Loads and Load Application ....................................................................................... 6.5 Structural Modeling................................................................................................................. 6.5.1 General ............................................................................................................................. 6.5.2 Jacket Structures............................................................................................................... 6.5.3 Floating Production and Offloading Systems (FPSO) ..................................................... 6.5.4 TLP, Spar and Semi-submersible ..................................................................................... 6.6 References ...............................................................................................................................

Introduction ...............................................................................................................................

100 100101 102 102 102 103 105 105 105 107 109 112 114 114 114 116 123 125

CHAPTER 7 LIMIT-STATE DESIGN OF OFFSHORE STRUCTURES

................

127127 128 128 129 130 134 134 135 137 138

7.1 Limit State Design ................................................................................................................... 7.2 Ultimate Limit State Design .................................................................................................... 7.2.1 Ductility and Brittle Fracture Avoidance......................................................................... 7.2.2 Plated Structures............................................................................................................... 7.2.3 Shell Structures ................................................................................................................ 7.3 Fatigue Limit State Design ...................................................................................................... 7.3.1 Introduction...................................................................................................................... 7.3.2 Fatigue Analysis............................................................................................................... 7.3.3 Fatigue Design ................................................................................................................. 7.4 References ...............................................................................................................................

Part 11: Ultimate StrengthCHAPTER 8 BUCKLINGKOLLAPSEOF COLUMNS AND BEAM-COLUMNS

................141141 141 143 144 145 145 146 147 148 148 148

8.1 Buckling Behavior and Ultimate Strength of Columns........................................................... 8.1.1 Buckling Behavior ........................................................................................................... 8.1.2 Peny-Robertson Formula................................................................................................. 8.1.3 Johnson-OstenfeldFormula ............................................................................................. 8.2 Buckling Behavior and Ultimate Strength of Beam-Columns ................................................ 8.2.1 Beam-Column with Eccentric Load ................................................................................. 8.2.2 Beam-Column with Initial Deflection and Eccentric Load .............................................. 8.2.3 Ultimate Strength of Beam-Columns ............................................................................... 8.2.4 Alternative Ultimate Strength Equation - Initial Yielding .............................................. 8.3 Plastic Design of Beam-Columns ............................................................................................ 8.3.1 Plastic Bending of Beam Cross-section ...........................................................................

X

Contents

8.3.2 Plastic Hinge Load ........................................................................................................... 8.3.3 Plastic Interaction Under Combined Axial Force and Bending 8.4 Examples ................................................................................................................................. 8.4.1 Example 8.1: Elastic Buckling of Columns with Alternative Boundaty Conditions 8.4.2 Example 8.2 Two Types of Ultimate Strength Buckling vs.Fracture ........................... 8.5 References ...............................................................................................................................

.......................................

.......

150 150 151 151 153 154 155 155 156 156 156 158 163 163 169 169

CHAPTER9 BUCKLING ANDLOCALBUCKLINGOFTUBULARMEMBERS

...............155

9.1 Introduction ............................................................................................................................. 9.1.1 General ............................................................................................................................. 9.1.2 Safety Factors for Offshore Strength Assessment............................................................ 9.2 Experiments............................................................................................................................. 9.2.1 Test Specimens................................................................................................................. 9.2.2 Material Tests................................................................................................................... 9.2.3 Buckling Test Procedures ................................................................................................ 9.2.4 Test Results ...................................................................................................................... 9.3 Theory of Analysis .................................................................................................................. 9.3.1 Simplified Elasto-Plastic Large Deflection Analysis....................................................... 9.3.2 Idealized Structural Unit Analysis 9.4 Calculation Results .................................................................................................................. 9.4.1 Simplified Elasto-Plastic Large Deflection Analysis....................................................... 9.4.2 Idealized Structural Unit Method Analysis...................................................................... 9.5 Conclusions ............................................................................................................................. 9.6 Example ................................................................................................................................... 9.7 References ...............................................................................................................................

...................................................................................

180186 186 190 194 195 196

CHAPTER 10 ULTIMATE STRENGTH OF PLATES AND STIFFENED PLATES

...............199202

10.1 Introduction ............................................................................................................................. 10.1.1 General ............................................................................................................................. 10.1.2 Solution of Differential Equation..................................................................................... 10.1.3 Boundary Conditions ....................................................................................................... 10.1.4 Fabrication Related Imperfections and In-Service Structural Degradation ..................... 10.1.5 Correction for Plasticity ................................................................................................... 10.2 Combined Loads...................................................................................................................... 10.2.1 Buckling - ServiceabilityLimit State .............................................................................. 10.2.2 Ultimate Strength- Ultimate Limit State 10.3 Buckling Strength of Plates ..................................................................................................... 10.4 Ultimate Strength of Un-Stiffened Plates................................................................................ 10.4.1 Long Plates and Wide Plates............................................................................................ 10.4.2 Plates Under Lateral Pressure .......................................................................................... 10.4.3 Shear Strength.................................................................................................................. 10.4.4 Combined Loads .............................................................................................................. 10.5 Ultimate Strength of Stiffened Panels ..................................................................................... 10.5.1 Beam-Column Buckling................................................................................................... 10.5.2 Tripping of Stiffeners....................................................................................................... 10.6 Gross Buckling of Stiffened Panels (Overall Grillage Buckling)............................................ 10.7 References ...............................................................................................................................

199 199 200 202 204 205 205 206 207 208 208 209 209 209 209 209 210 210 210

........................................................................

CHAPTER 11 ULTIMATE STRENGTH OF CYLINDRICALSHELLS 11.1 Introduction ............................................................................................................................. 11.1.1 General ............................................................................................................................. 11.1.2 Buckling Failure Modes ................................................................................................... 11.2 Elastic Buckling of Unstiffened Cylindrical Shells.................................................................

..................

213213 213 214 215

Contents 11.2.1 Equilibrium Equations for Cylindrical Shells.................................................................. 11.2.2 Axial Compression ........................................................................................................... 11.2.3 Bending ............................................................................................................................ 11.2.4 External Lateral Pressure ................................................................................................. 11.3 Buckling of Ring Stiffened Shells ........................................................................................... 1 1.3.1 Axial Compression........................................................................................................... 11.3.2 Hydrostatic Pressure......................................................................................................... 11.3.3 Combined Axial Compressionand Pressure.................................................................... 11.4 Buckling of Stringer and Ring Stiffened Shells....................................................................... 11.4.1 Axial Compression........................................................................................................... 1 1.4.2 Radial Pressure................................................................................................................. 11.4.3 Axial Compression and Radial Pressure .......................................................................... 11.5 References ............................................................................................................................... CHAPTER 12 A THEORY OF NONLINEAR FINITE ELEMENT ANALYSIS

xi215 216 217 218 219 219 220 221 221 221 223 223 224 227 227 228 229 229 230 233 235 236 237 237 239 240 242 246 247 248 251 251 252 252 254 257 257 257 259 260 260 261 263 264 265 265 266 267 269 271 271

............

12.1 General..................................................................................................................................... 12.2 Elastic Beam-Column With Large Displacements.................................................................. 12.3 The Plastic Node Method ........................................................................................................ 12.3.1 History of the Plastic Node Method................................................................................. 12.3.2 Consistency Condition and Hardening Rates for Beam Cross-Sections.......................... 12.3.3 Plastic Displacementand Strain at Nodes ........................................................................ 12.3.4 Elastic-Plastic Stiffness Equation for Elements ............................................................... 12.4 Transformation Matrix............................................................................................................. 12.5 Appendix A: Stress-BasedPlasticity Constitutive Equations.................................................. 12.5.1 General ............................................................................................................................. 12.5.2 Relationship Between Stress and Strain in Elastic Region .............................................. 12.5.3 Yield Criterion ................................................................................................................. 12.5.4 Plastic Strain Increment ................................................................................................... 12.5.5 Stress Increment- Strain Increment Relation in Plastic Region ...................................... 12.6 Appendix B: DeformationMatrix ........................................................................................... 12.7 References ............................................................................................................................... CHAPTER 13 COLLAPSE ANALYSIS OF SHIP HULLS

...........................................................

13.1 Introduction ............................................................................................................................. 13.2 Hull Structural Analysis Based on the Plastic Node Method .................................................. 13.2.1 Beam-Column Element.................................................................................................... 13.2.2 Attached Plating Element................................................................................................. 13.2.3 Shear Panel Element ........................................................................................................ 13.2.4 Non-Linear Spring Element ............................................................................................. 13.2.5 Tension Tearing Rupture.................................................................................................. 13.2.6 Computational Procedures ............................................................................................... 13.3 Analytical Equations for Hull Girder Ultimate Strength......................................................... 13.3.1 Ultimate Moment Capacity Based on Elastic Section Modulus ...................................... 13.3.2 Ultimate Moment Capacity Based on Fully Plastic Moment ........................................... 13.3.3 Proposed Ultimate Strength Equations ............................................................................ 13.4 Modified Smith Method Accounting for Corrosion and Fatigue Defects ............................... 13.4.1 Tensile and Comer Elements ........................................................................................... 13.4.2 Compressive Stiffened Panels .......................................................................................... rc 13.4.3 C a k Propagation Prediction........................................................................................... 13.4.4 Corrosion Rate Model ...................................................................................................... 13.5 Comparisons of Hull Girder Strength Equations and Smith Method ...................................... 13.6 Numerical Examples Using the Proposed Plastic Node Method ............................................. 13.6.1 Collapse of a Stiffened Plate ............................................................................................

xii

Contents13.6.2 Collapse of an Upper Deck Structure............................................................................... 13.6.3 Collapse of Stiffened Box Girders ................................................................................... 13.6.4 Ultimate Longitudinal Strength of Hull Girders .............................................................. 13.6.5 Quasi-Static Analysis of a Side Collision ........................................................................ 13.7 Conclusions ............................................................................................................................. 13.8 References ............................................................................................................................... 273 274 276 278 279 280

CHAPTER 14 OFFSHORE STRUCTURES UNDER IMPACT LOADS

..................

285

14.1 General..................................................................................................................................... 285 14.2 Finite Element Formulation..................................................................................................... 286 286 14.2.1 Equations of Motion......................................................................................................... 14.2.2 Load-DisplacementRelationship ofthe Hit Member ...................................................... 286 14.2.3 Beam-Column Element for Modeling of the Struck Structure......................................... 287 287 14.2.4 Computational Procedure................................................................................................. 14.3 Collision Mechanics ................................................................................................................ 289 289 14.3.1 Fundamental Principles.................................................................................................... 14.3.2 Conservation of Momentum ............................................................................................ 289 14.3.3 Conservation of Energy.................................................................................................... 290 14.4 Examples ................................................................................................................................. 291 14.4.1 Mathematical Equations for Impact Forces and Energies in ShiplPlafformCollisions...29 1 14.4.2 Basic Numerical Examples .............................................................................................. 292 14.4.3 Application to Practical Collision Problems .................................................................... 298 14.5 Conclusions ............................................................................................................................. 303 14.6 References ............................................................................................................................... 303

CHAPTER 15 OFFSHORE STRUCTURES UNDER EARTHQUAKE LOADS

............

305

15.1 General..................................................................................................................................... 305 15.2 Earthquake Design as per API RP2A ...................................................................................... 305 307 15.3 Equations and Motion.............................................................................................................. 15.3.1 Equation of Motion .......................................................................................................... 307 15.3.2 Nonlinear Finite Element Model ...................................................................................... 308 15.3.3 Analysis Procedure........................................................................................................... 308 308 15.4 Numerical Examples................................................................................................................ 15.5 Conclusions ............................................................................................................................. 313 15.6 References ............................................................................................................................... 314

Part 111: Fatigue and FractureCHAPTER 16 MECHANISM OF FATIGUE AND FRACTURE16.1 16.2 16.3 16.4 16.5 16.6 16.7 16.8

........................

317317 317 318 320 321 323 325 326

Introduction ............................................................................................................................. Fatigue Overview .................................................................................................................... Stress-ControlledFatigue ........................................................................................................ Cumulative Damage for Variable Amplitude Loading............................................................ Strain-ControlledFatigue ........................................................................................................ Fracture Mechanics in Fatigue Analysis.................................................................................. Examples ................................................................................................................................. References ...............................................................................................................................

CHAPTER 17 FATIGUE CAPACITY

............................................................................................

329329 329 33 1

17.1 S-N Curves .............................................................................................................................. 17.1.1 General ............................................................................................................................. 17.1.2 Effect of Plate Thickness .................................................................................................

Contents17.1.3 Effect of Seawater and Corrosion Protection................................................................... 17.1.4 Effect of Mean Stress ....................................................................................................... 17.1.5 Comparisons of S-N Curves in Design Standards............................................................ 17.1.6 Fatigue Strength Improvement......................................................................................... 17.1.7 Experimental S-NCurves................................................................................................. 17.2 Estimation of the Stress Range ................................................................................................ 17.2.1 Nominal Stress Approach................................................................................................. 17.2.2 Hotspot Stress Approach.................................................................................................. 17.2.3 Notch Stress Approach..................................................................................................... 17.3 Stress ConcentrationFactors ................................................................................................... 17.3.1 Definition of Stress ConcentrationFactors ...................................................................... 17.3.2 Determination of SCF by ExperimentalMeasurement .................................................... 17.3.3 Parametric Equations for Stress Concentration Factors................................................... 17.3.4 Hot-Spot Stress Calculation Based on Finite Element Analysis ...................................... 17.4 Examples ................................................................................................................................. 17.4.1 Example 17.1: Fatigue Damage Calculation.................................................................... 17.5 References ...............................................................................................................................

xiii 331 331 332 335 335 336 336 337 339 339 339 340 340 341 343 343 344

CHAPTER 18 FATIGUE LOADING AND STRESSES

................................................................

347347 348 350 350 350 351 352 354 354 354 355 355 355 356 357 361 361

18.1 Introduction ............................................................................................................................. 18.2 Fatigue Loading for Ocean-Going Ships................................................................................. 18.3 Fatigue Stresses ....................................................................................................................... 18.3.1 General ............................................................................................................................. 18.3.2 Long Term Fatigue Stress Based on Weibull Distribution .............................................. 18.3.3 Long Term Stress Distribution Based on Deterministic Approach.................................. 18.3.4 Long Term Stress Distribution- Spectral Approach ....................................................... 18.4 Fatigue Loading Defined Using Scatter Diagrams.................................................................. 18.4.1 General ............................................................................................................................. 18.4.2 Mooring and Riser Induced Damping in Fatigue Seastates ............................................. 18.5 Fatigue Load Combinations..................................................................................................... 18.5.1 General ............................................................................................................................. 18.5.2 Fatigue Load Combinations for Ship Structures.............................................................. 18.5.3 Fatigue Load Combinations for Offshore Structures ....................................................... 18.6 Examples ................................................................................................................................. 18.7 Concluding Remarks ............................................................................................................... 18.8 References ...............................................................................................................................

CHAPTER 19 SIMPLIFIEDFATIGUE ASSESSMENT

..............................................................

363363 364 365 365 366 366 367 367 367 368 370 371

19.1 introduction ............................................................................................................................. 19.2 Deterministic Fatigue Analysis................................................................................................ 19.3 Simplified Fatigue Assessment................................................................................................ 19.3.1 Calculation of Accumulated Damage .............................................................................. 19.3.2 Weibull Stress Distribution Parameters ........................................................................... 19.4 Simplified Fatigue Assessment for Bilinear S-N Curves ........................................................ 19.5 Allowable Stress Range ........................................................................................................... 19.6 Design Criteria for Connections Around Cutout Openings..................................................... 19.6.1 General ............................................................................................................................. 19.6.2 Stress Criteria for Collar Plate Design ............................................................................. 19.7 Examples ................................................................................................................................. 19.8 References ...............................................................................................................................

CHAPTER 20 SPECTRAL FATIGUE ANALYSIS AND DESIGN 20.1 Introduction .............................................................................................................................

.............................................

373373

xiv

Contents

20.1.1 General ............................................................................................................................. 373 20.1.2 Terminology..................................................................................................................... 374 20.2 Spectral Fatigue Analysis ........................................................................................................ 374 20.2.1 Fatigue Damage Acceptance Criteria............................................................................... 374 20.2.2 Fatigue Damage Calculated Using Frequency Domain Solution..................................... 374 377 20.3 Time-Domain Fatigue Assessment.......................................................................................... 20.3.1 Application....................................................................................................................... 377 20.3.2 Analysis Methodology for TimeDomain Fatigue of Pipelines ....................................... 377 20.3.3 Analysis Methodology for Time-Domain Fatigue of Risers............................................ 378 20.3.4 Analysis Methodology for Time-Domain Fatigue of Nonlinear Ship Response .............378 20.4 Structural Analysis .................................................................................................................. 379 20.4.1 Overall Structural Analysis .............................................................................................. 379 381 20.4.2 Local Structural Analysis................................................................................................. 20.5 Fatigue Analysis and Design ................................................................................................... 381 20.5.1 Overall Design ................................................................................................................. 381 382 20.5.2 Stress Range Analysis ...................................................................................................... 20.5.3 Spectral Fatigue Parameters............................................................................................. 382 20.5.4 Fatigue Damage Assessment............................................................................................ 387 20.5.5 Fatigue Analysis and Design Checklist............................................................................ 388 20.5.6 Drawing Verification ....................................................................................................... 389 20.6 Classification Society Interface ............................................................................................... 389 389 20.6.1 Submittal and Approval of Design Brief.......................................................................... 20.6.2 Submittal and Approval of Task Report .......................................................................... 389 20.6.3 Incorporation of Comments from Classification Society................................................. 389 20.7 References ............................................................................................................................... 389

CHAPTER 21 APPLICATION OF FRACTURE MECHANICS

.........................

391

21.1 Introduction ............................................................................................................................. 391 21.1.1 General ............................................................................................................................. 391 21.1.2 Fracture Mechanics Design Check................................................................................... 391 392 21.2 Level 1: The CTOD Design Curve .......................................................................................... 21.2.1 The Empirical Equations.................................................................................................. 392 21.2.2 The British Welding Institute (CTODDesign Curve) ..................................................... 393 394 21.3 Level 2: The CEGB R6 Diagram............................................................................................. 21.4 Level 3: The Failure Assessment Diagram (FAD) .................................................................. 395 396 21.5 Fatigue Damage Estimation Based on Fracture Mechanics .................................................... 21.5.1 Crack Growth Due to Constant Amplitude Loading ........................................................ 396 21.5.2 Crack Growth due to Variable Amplitude Loading......................................................... 397 21.6 Comparison of Fracture Mechanics & S-N Curve Approaches for Fatigue Assessment........397 21.7 Fracture Mechanics Applied in Aerospace, Power Generation Industries .............................. 398 2 1.8 Examples ................................................................................................................................. 399 399 21.9 References ...............................................................................................................................

CHAPTER 22 MATERIAL SELECTIONS AND DAMAGE TOLERANCE CRITERIA

........401401 401 401 402 402 403 403 403 404

22.1 Introduction ............................................................................................................................. 22.2 Material Selections and Fracture Prevention........................................................................... 22.2.1 Material Selection ............................................................................................................ 22.2.2 Higher Strength Steel ....................................................................................................... 22.2.3 Prevention of Fracture...................................................................................................... 22.3 Weld Improvementand Repair................................................................................................ 22.3.1 General............................................................................................................................. 22.3.2 Fatigue-ResistantDetails ................................................................................................. 22.3.3 Weld Improvement...........................................................................................................

Contents22.3.4 Modification of Residual Stress Distribution................................................................... 22.3.5 Discussions....................................................................................................................... 22.4 Damage Tolerance Criteria...................................................................................................... 22.4.1 General ............................................................................................................................. 22.4.2 Residual Strength Assessment Using Failure Assessment Diagram................................ 22.4.3 Residual Life Prediction Using Paris Law ....................................................................... 22.4.4 Discussions....................................................................................................................... 22.5 Non-Destructive Inspection..................................................................................................... 22.6 References ...............................................................................................................................

xv

405 405 406 406 406 407 407 407 408

Part IV: Structural ReliabilityCHAPTER 23 BASICS OF STRUCTURAL RELIABILITY

........................................................

413

23.1 Introduction ............................................................................................................................. 23.2 Uncertainty and Uncertainty Modeling ................................................................................... 23.2.1 General ............................................................................................................................. 23.2.2 Natural vs.Modeling Uncertainties ................................................................................. 23.3 Basic Concepts ........................................................................................................................ 23.3.1 General ............................................................................................................................. 23.3.2 Limit State and Failure Mode........................................................................................... 23.3.3 Calculation of Structural Reliability ................................................................................ 23.3.4 Calculation by FORM ...................................................................................................... 23.3.5 Calculation by S O W ...................................................................................................... 23.4 Component Reliability.............................................................................................................. 23.5 System Reliability Analysis..................................................................................................... 23.5.1 General ............................................................................................................................. 23.5.2 Series System Reliability ................................................................................................. 23.5.3 Parallel System Reliability............................................................................................... 23.6 Combination of Statistical Loads............................................................................................. 23.6.1 General ............................................................................................................................. 23.6.2 Turkstras Rule ................................................................................................................. 23.6.3 Feny Borges-CastanhetaModel....................................................................................... 23.7 Time-Variant Reliability.......................................................................................................... 23.8 Reliability Updating................................................................................................................. 23.9 Target Probability.................................................................................................................... 23.9.1 General ............................................................................................................................. 23.9.2 Target Probability............................................................................................................. 23.9.3 Recommended Target Safety Indices for Ship Structures................................................ Software for Reliability Calculations.............................................................................. 23.10 Numerical Examples ....................................................................................................... 23.1 1 23.1 1.1 Example 23.1 : Safety Index Calculation of a Ship Hull ............................................. ehd 23.1 1.2 Example 23.2: p Safety Index M t o ....................................................................... 23.1 1.3 Example 23.3: Reliability Calculation of Series System ............................................ 23.1 I .4 Example 23.4: Reliability Calculation of Parallel System ......................................... 23.12 References....................................................................................................................... CHAPTER 24 RANDOM VARIABLES AND UNCERTAINTY ANALYSIS

413 413 413 414 415 415 415 415 419 420 421 421 421 421 421 422 422 423 423 424 425 426 426 426 427 427 427 427 428 429 430 431

..............

433433 433 433 433 434

24.1 Introduction ............................................................................................................................. 24.2 Random Variables ................................................................................................................... 24.2.1 General ............................................................................................................................. 24.2.2 Statistical Descriptions..................................................................................................... 24.2.3 Probabilistic Distributions................................................................................................

m i

Contents436 436 437 438 438 438 439 440 441

24.3 Uncertainty Analysis ............................................................................................................... 24.3.1 Uncertainty Classification................................................................................................ 24.3.2 Uncertainty Modeling ...................................................................................................... 24.4 Selection of Distribution Functions......................................................................................... 24.5 Uncertainty in Ship Structural Design ..................................................................................... 24.5.1 General............................................................................................................................. 24.5.2 Uncertainties in Loads Acting on Ships........................................................................... 24.5.3 Uncertainties in Ship Structural Capacity........................................................................ 24.6 References ...............................................................................................................................

CHAPTER 25 RELIABILITY OF SHIP STRUCTURES

.............................................................

443443

25.1 General..................................................................................................................................... 25.2 Closed Form Method for Hull Girder Reliability.................................................................... 25.3 Load Effects and Load Combination....................................................................................... 25.4 Procedure for Reliability Analysis of Ship Structures............................................................. 25.4.1 General ............................................................................................................................. 25.4.2 Response Surface Method ................................................................................................ 25.5 Time-Variant Reliability Assessment of FPSO Hull Girders.................................................. 25.5.1 Load Combination Factors............................................................................................... 25.5.2 Time-Variant Reliability Assessment .............................................................................. 25.5.3 Conclusions...................................................................................................................... 25.6 References ...............................................................................................................................

44 4445 448 448 448 450 452 454 459 459

CHAPTER 26 RELIABILITY-BASEDDESIGN AND CODE CALIBRATION

............

463463 463 463 463 464 465 465 465 466 466 467 468 468 468 469 469 471 471 471 472 473 474 475 476 479

26.1 General..................................................................................................................................... 26.2 General Design Principles ....................................................................................................... 26.2.1 Concept of Safety Factors ................................................................................................ 26.2.2 Allowable Stress Design .................................................................................................. 26.2.3 Load and Resistance Factored Design ............................................................................. 26.2.4 Plastic Design ................................................................................................................... 26.2.5 Limit State Design (LSD) ................................................................................................ 26.2.6 Life Cycle Cost Design .................................................................................................... 26.3 Reliability-BasedDesign ......................................................................................................... 26.3.1 General ............................................................................................................................. 26.3.2 Application of Reliability Methods to ASD Format ........................................................ 26.4 Reliability-BasedCode Calibrations ....................................................................................... 26.4.1 General ............................................................................................................................. 26.4.2 Code Calibration Principles ............................................................................................. 26.4.3 Code Calibration Procedure ............................................................................................. 26.4.4 Simple Example of Code Calibration............................................................................... 26.5 Numerical Example for Tubular Structure .............................................................................. 26.5.1 Case Description .............................................................................................................. 26.5.2 Design Equations ............................................................................................................. 26.5.3 Limit State Function (LSF) .............................................................................................. 26.5.4 Uncertainty Modeling ...................................................................................................... 26.5.5 Target Safely Levels ........................................................................................................ 26.5.6 Calibration of Safety Factors............................................................................................ 26.6 Numerical Example for Hull Girder Collapse of FPSOs......................................................... 26.7 References ...............................................................................................................................

CHAPTER 27 FATIGUE RELIABILITY 481 27.1 Introduction ............................................................................................................................. 481 27.2 Uncertainty in Fatigue Stress Model ....................................................................................... 481

.......................................................................................

Contents

xvii 481 482 483 483 484 484 487 488 489 489 489 490 490 491 496

27.2. I Stress Modeling................................................................................................................ 27.2.2 Stress Modeling Error ...................................................................................................... 27.3 Fatigue Reliability Models ...................................................................................................... 27.3.1 Introduction...................................................................................................................... 27.3.2 Fatigue Reliability S-N Approach ................................................................................. 27.3.3 Fatigue Reliability Fracture Mechanics (FM) Approach ............................................... 27.3.4 Simplified Fatigue Reliability Model - Lognormal Format............................................. 27.4 Calibration of FM Model by S-N Approach............................................................................ 27.5 Fatigue Reliability Application . Fatigue Safety Check.......................................................... 27.5.1 Target Safety Index for Fatigue ....................................................................................... 27.5.2 Partial Safety Factors ....................................................................................................... 27.6 Numerical Examples................................................................................................................ 27.6.1 Example 27.1 : Fatigue Reliability Based on Simple S-N Approach................................ 27.6.2 Example 27.2: Fatigue Reliability of Large Aluminum Catamaran................................. 27.7 References ...............................................................................................................................

-

CHAPTER 28 PROBABILITYAND RISK BASED INSPECTION PLANNING

...........

497497 497 500 500 500 502 506 512

28.1 Introduction ............................................................................................................................. 28.2 Concepts for Risk Based Inspection Planning......................................................................... 28.3 Reliability Updating Theory for Probability-BasedInspection Planning................................ 28.3.1 General ............................................................................................................................. 28.3.2 Inspection Planning for Fatigue Damage ......................................................................... 28.4 Risk Based Inspection Examples ............................................................................................. 28.5 Risk Based 'Optimum' Inspection........................................................................................... 28.6 References ...............................................................................................................................

Part V: Risk AssessmentCHAPTER 29 RISK ASSESSMENT METHODOLOGY

.............................................................

515515 515 515 516 517 517 518 518 519 519 520 520 520 520 522 522 522 522 523 524 525 525 525

29.1 Introduction ............................................................................................................................. 29.1.1 Health, Safety and EnvironmentProtection..................................................................... 29.1.2 Overview of Risk Assessment.......................................................................................... 29.1.3 Planning of Risk Analysis................................................................................................ 29.1.4 System Description .......................................................................................................... 29.1.5 Hazard Identification........................................................................................................ 29.1.6 Analysis of Causes and Frequency of Initiating Events................................................... 29.1.7 Consequence and Escalation Analysis ............................................................................. 29.1.8 Risk Estimation................................................................................................................ 29.1.9 Risk Reducing Measures.................................................................................................. 29.1.10 Emergency Preparedness............................................................................................ 29.1.1 1 Time-VariantRisk ...................................................................................................... 29.2 Risk Estimation........................................................................................................................ 29.2.1 Risk to Personnel.............................................................................................................. 29.2.2 Risk to Environment ........................................................................................................ 29.2.3 Risk to Assets (Material Damage and Production LossDelay) ....................................... 29.3 Risk Acceptance Criteria ......................................................................................................... 29.3.1 General ............................................................................................................................. 29.3.2 Risk Matrices ................................................................................................................... 29.3.3 ALARP-Principle............................................................................................................. 29.3.4 Comparison Criteria ......................................................................................................... 29.4 Using Risk Assessment to Determine Performance Standard................................................. 29.4.1 General .............................................................................................................................

xviii

Contents

29.4.2 Risk-Based Fatigue Criteria for Critical Weld Details..................................................... 2 . . Risk-Based Compliance Process for Engineering Systems ............................................. 943 29.5 References ...............................................................................................................................CHAPTER 30 RISK ASSESSMENT APPLIED TO OFFSHORE STRUCTURES

526 526 527 529 530 530 530 532 533 533 534 535 535 536 538 538 539 540 541 541 541 543 544 545 545 546 547 548 550 551 552 553

...................529

30.1 Introduction ............................................................................................................................. 30.2 Collision Risk .......................................................................................................................... 3 . . Colliding Vessel Categories............................................................................................. 021 30.2.2 Collision Frequency ......................................................................................................... 3 . . Collision Consequence..................................................................................................... 023 30.2.4 Collision Risk Reduction ................................................................................................. 30.3 Explosion Risk......................................................................................................................... 30.3.1 Explosion Frequency........................................................................................................ 30.3.2 Explosion Load Assessment............................................................................................. 30.3.3 Explosion Consequence................................................................................................... 30.3.4 Explosion Risk Reduction................................................................................................ 30.4 Fire Risk .................................................................................................................................. 3 . . Fire Frequency ................................................................................................................. 041 30.4.2 Fire Load and Consequence Assessment......................................................................... 30.4.3 Fire Risk Reduction.......................................................................................................... 30.4.4 Guidance on Fire and Explosion Design .......................................................................... 3 . Dropped Objects...................................................................................................................... 05 3 . . Frequency of Dropped Object Impact .............................................................................. 051 3 . . Drop Object Impact Load Assessment............................................................................. 052 30.5.3 Consequence of Dropped Object Impact ......................................................................... 30.6 Case Study - Risk Assessment of Floating Production Systems............................................. 30.6.1 General ............................................................................................................................. 30.6.2 Hazard Identification........................................................................................................ 30.6.3 Risk Acceptance Criteria.................................................................................................. 30.6.4 Risk Estimation and Reducing M a u e ......................................................................... esrs 30.6.5 Comparative Risk Analysis.............................................................................................. 30.6.6 Risk Based Inspection...................................................................................................... 30.7 Environmental Impact Assessment.......................................................................................... 30.8 References ............................................................................................................................... 3 11 Introduction ............................................................................................................................. . 31.2 Overview of Formal Safety Assessment.................................................................................. 3 13 Functional Components of Formal Safety Assessment........................................................... . 3 131 System Definition............................................................................................................. .. 31.3.2 Hazard Identification........................................................................................................ 3 1 3 3 Frequency Analysis of Ship Accidents ............................................................................ .. 31.3.4 Consequence of Ship Accidents....................................................................................... 31.3.5 Risk Evaluation................................................................................................................ 3 1 3 6 Risk Control and Cost-Benefit Analysis .......................................................................... .. 3 1 4 Human and OrganizationalFactors in FSA ............................................................................. . 31.5 An Example Application to Ship's Fuel Systems.................................................................... 31.6 Concerns Regarding the Use of FSA in Shipping ................................................................... 31.7 References ...............................................................................................................................CHAPTER 32 ECONOMIC RISK ASSESSMENT FOR FIELD DEVELOPMENT

CHAPTER 31 FORMAL SAFETY ASSESSMENTAPPLIED TO SHIPPING INDUSTRY 555

...

555 556 557 557 559 562 563 564 564 565 565 566 567569 569

.................569

3 . Introduction ............................................................................................................................. 21 3 . . Field Development Phases ............................................................................................... 211

Contents

XiX

32.1.2 Background of Economic Evaluation .............................................................................. 32.1.3 QuantitativeEconomic Risk Assessment......................................................................... 32.2 Decision Criteria and Limit State Functions............................................................................ 32.2.1 Decision and Decision Criteria ........................................................................................ 32.2.2 Limit State Functions ............................................... 32.3 Economic Risk Modeling ........................................................................................................ 32.3.1 Cost Variable Modeling ................................................................................................... 32.3.2 Income Variable Modeling............................................................................................... 32.3.3 Failure Probability Calculation ...... 32.4 Results Evaluation ................................. 32.4.1 Importance and Omission Factors.. ............................................. ............................................. 32.4.2 Sensitivity Factors ............................ 32.4.3 Contingency Factors....................... ............................................. 32.5 References ............................................................................................................................... CHAPTER 33 HUMAN RELIABILITY ASSESSMENT

570 570 571 571 572 572 573 575 575 576 576 579

..............................................................

33.1 Introduction ............................................................................................................................. 579 33.2 Human Error Identification...................................................................................................... 580 33.2.1 Problem Definition ........................................................................................................... 580 33.2.2 Task Analysis................................................................................................................... 580 33.2.3 Human Error Identification.............................................................................................. 581 33.2.4 Representation.................................................................................................................. 582 582 33.3 Human Error Analysis ............................................................................................................. 582 33.3.1 Human Error Quantification............................................................................................. 582 33.3.2 Impact Assessment........................................................................................................... 33.4 Human Error Reduction........................................................................................................... 583 33.4.1 Error Reduction...............................................................................................................