Page 17 - Marine Structural Design

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
20.3 Time-Domain Fatigue Assessment .......................................................................................... 377
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
20.4.2 Local Structural Analysis .................................................................................................
20.5 Fatigue Analysis and Design ................................................................................................... 381
381
20.5.1 Overall Design ................................................................................................................. 381
20.5.2 Stress Range Analysis ...................................................................................................... 382
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
20.6.1 Submittal and Approval of Design Brief .......................................................................... 389
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
21.2 Level 1: The CTOD Design Curve .......................................................................................... 392
21.2.1 The Empirical Equations .................................................................................................. 392
21.2.2 The British Welding Institute (CTOD Design Curve) ..................................................... 393
21.3 Level 2: The CEGB R6 Diagram ............................................................................................. 394
21.4 Level 3: The Failure Assessment Diagram (FAD) .................................................................. 395
21.5 Fatigue Damage Estimation Based on Fracture Mechanics .................................................... 396
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
21.9 References ............................................................................................................................... 399
CHAPTER 22 MATERIAL SELECTIONS AND DAMAGE TOLERANCE CRITERIA ........ 401
22.1 Introduction ............................................................................................................................. 401
22.2 Material Selections and Fracture Prevention ........................................................................... 401
22.2.1 Material Selection ............................................................................................................ 401
22.2.2 Higher Strength Steel ....................................................................................................... 402
22.2.3 Prevention of Fracture ...................................................................................................... 402
22.3 Weld Improvement and Repair ................................................................................................ 403
22.3.1 General ............................................................................................................................. 403
22.3.2 Fatigue-Resistant Details ................................................................................................. 403
22.3.3 Weld Improvement ........................................................................................................... 404