wb_fat

ANSYS Mechanical FATJACK User Manual

Release 14.0ANSYS, Inc.

November 2011Southpointe

275 Technology Drive

Canonsburg, PA 15317 ANSYS, Inc. is

certified to ISO

9001:[email protected]

http://www.ansys.com

(T) 724-746-3304

(F) 724-514-9494

Copyright and Trademark Information

© 2011 SAS IP, Inc. All rights reserved. Unauthorized use, distribution or duplication is prohibited.

ANSYS, ANSYS Workbench, Ansoft, AUTODYN, EKM, Engineering Knowledge Manager, CFX, FLUENT, HFSS and any

and all ANSYS, Inc. brand, product, service and feature names, logos and slogans are registered trademarks or

trademarks of ANSYS, Inc. or its subsidiaries in the United States or other countries. ICEM CFD is a trademark used

by ANSYS, Inc. under license. CFX is a trademark of Sony Corporation in Japan. All other brand, product, service

and feature names or trademarks are the property of their respective owners.

Disclaimer Notice

THIS ANSYS SOFTWARE PRODUCT AND PROGRAM DOCUMENTATION INCLUDE TRADE SECRETS AND ARE CONFID-

ENTIAL AND PROPRIETARY PRODUCTS OF ANSYS, INC., ITS SUBSIDIARIES, OR LICENSORS. The software products

and documentation are furnished by ANSYS, Inc., its subsidiaries, or affiliates under a software license agreement

that contains provisions concerning non-disclosure, copying, length and nature of use, compliance with exporting

laws, warranties, disclaimers, limitations of liability, and remedies, and other provisions. The software products

and documentation may be used, disclosed, transferred, or copied only in accordance with the terms and conditions

of that software license agreement.

ANSYS, Inc. is certified to ISO 9001:2008.

U.S. Government Rights

For U.S. Government users, except as specifically granted by the ANSYS, Inc. software license agreement, the use,

duplication, or disclosure by the United States Government is subject to restrictions stated in the ANSYS, Inc.

software license agreement and FAR 12.212 (for non-DOD licenses).

Third-Party Software

See the legal information in the product help files for the complete Legal Notice for ANSYS proprietary software

and third-party software. If you are unable to access the Legal Notice, please contact ANSYS, Inc.

Published in the U.S.A.

Table of Contents

1. FATJACK Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2. FATJACK Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.1. Fatigue Assessment .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.2. S-N Curves .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.3. Miner's Rule .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.4. Deterministic Methods .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2.5. Spectral Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.6. Time History Methods .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.7. Strategies for Wave Fatigue Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.8. Parametric SCF Equations .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3. FATJACK Analysis Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

3.1. Overview .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

3.2. Environmental Information .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

3.3. Joint Selection .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

3.4. Joint Classification .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

3.5. Inspection Points ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3.5.1. Tubular Joint Inspection Points ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3.5.2. Tubular Butt Joints ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3.5.3. Non-Tubular Braces .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

3.6. Design Information .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

3.6.1. Design Geometry .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

3.6.2. Secondary Elements .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

3.7. Stress Concentration Factors ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

3.7.1. Explicit SCF Definitions .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

3.7.2. Empirical SCF Formulations .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

3.7.3. Influence Functions .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

3.7.4. SCF Interpolation .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

3.7.5. Annotated SCF File Generation .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

3.8. S-N Curves .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

3.9. Units ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

3.10. Element Cross Sections .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

3.11. Results presentation .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

4. FATJACK Command Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

4.1. FATJACK Free Format Syntax .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

4.1.1. General Description .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

4.1.2. Special Symbols ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

4.2. FATJACK Priority of Data Assignments .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

4.3. Preliminary Data .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

4.4. Fatigue Analysis method .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

4.4.1. ANALYSIS command .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

4.4.2. Deterministic Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

4.4.2.1. Deterministic Analysis Example .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

4.4.3. Spectral Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

4.4.3.1. Spectral Analysis Example .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

4.4.4. Stress History Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

4.4.4.1. Stress History Analysis Example .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

4.4.5. Time History Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

4.4.5.1. Time History Analysis Example .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

4.5. ACCE .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

4.6. ALLOWABLE .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

iiiRelease 14.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information

of ANSYS, Inc. and its subsidiaries and affiliates.

4.7. ANSYS .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

4.8. CHORD ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

4.9. COMPONENT .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

4.10. CURVE .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

4.10.1. CURVE Command (User defined S-N curves) ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

4.10.2. CURVE Command (Base thickness definition for standard curves) ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

4.11. CYCLE .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

4.12. DESIGN .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

4.13. DETE .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

4.14. END .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

4.15. FILES .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

4.16. FREQUENCY .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

4.17. GAP .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

4.18. GAPDEFAULT .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

4.19. HIST .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

4.20. INSET .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

4.21. INSPECTION ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

4.21.1. INSPECTION Command (Tubular sections) ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

4.21.2. INSPECTION Command (Non-tubular sections) ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

4.22. JOB .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

4.23. JOINT .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

4.24. LIMIT .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

4.25. NEWSTRUCTURE .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

4.26. OPTIONS .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

4.27. PARAMETER .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

4.28. PRINT .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

4.29. PROJECT .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

4.30. REDUCTION ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

4.31. RESU .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

4.32. SCF Definition .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

4.32.1. SCFANGLE Command .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

4.32.2. SCF AUTO DEFAULT Command .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

4.32.3. SCF AUTO JOINT Command .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

4.32.4. SCFBRACE Command .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

4.32.5. SCF DEFAULT Command .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

4.32.6. SCFJOINT Command .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

4.32.7. SCFMINIMUM Command .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

4.32.8. SCFPOINT Command .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

4.33. SECONDARY .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

4.34. SIGM ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

4.35. S-N .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

4.36. SPECTRUM ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

4.37. SPREADING .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

4.38. STOP .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

4.39. STRUCTURE .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

4.40. SYSTEM ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

4.41. TEXT .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

4.42. THICKNESS .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

4.43. TITLE .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

4.44. TRANSFER .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

4.45. TYPE .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

4.46. UNITS .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

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4.47. WAVE .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

4.48. YEAR .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

5. FATJACK Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

5.1. Running FATJACK .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

5.1.1. ASAS Files Required by FATJACK .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

5.1.2. Files saved by FATJACK .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

5.2. Section Profile Information .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

5.2.1. BOX - Symmetric Fabricated Box Section .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

5.2.2. RHS - Rolled Hollow Section .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

5.2.3.TUB - Tubes of Circular Section .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

5.2.4. WF - Wide Flanged Rolled I-Section .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

5.3. FATJACK References .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

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Chapter 1: FATJACK Introduction

FATJACK (FATigue calculations for offshore JACKets) is the fatigue calculation module. FATJACK is used

for the estimation of fatigue life for tubular and beam joints, employing deterministic or spectral

methods.

FATJACK represents a complete revamp of the philosophy as to how joint fatigue calculations are un-

dertaken, and embodies many new features that assist the designer in attaining optimal results with

the minimum of supplied data. The following facilities are provided by FATJACK.

• Automatic retrieval of wave information from analysis databases

• Selective processing of individual joints using node data

• Design override capabilities to allow user defined joint configuration, member properties and secondary

members

• Ability to compute SCF values at joints consisting of 1, 2 or 3 analysis node points

• SCF values for a brace may be computed automatically using Kuang, Wordsworth, DS449 or Efthymiou

formulations

• SCF values for a given brace may be computed from more than one empirical equation set allowing

the most appropriate equations to be adopted for specific inspection points around the brace

• Computed SCFs may be output to a formatted file for modification and utilization in subsequent FATJACK

runs

• Selective application of Marshall reduction factor and S-N thickness correction

• S-N data may be input using standard pre-defined curves. User defined curves may now define a cut-

off value

• Completely revised input data syntax allowing greater flexibility in data preparation

A brief overview of the analysis methods available is provided. For more detailed information see Ref.

1.

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Chapter 2: FATJACK Theory

This section discusses the following topics:

2.1. Fatigue Assessment

2.2. S-N Curves

2.3. Miner's Rule

2.4. Deterministic Methods

2.5. Spectral Analysis

2.6.Time History Methods

2.7. Strategies for Wave Fatigue Analysis

2.8. Parametric SCF Equations

2.1. Fatigue Assessment

Steel members subjected to a sufficiently large fluctuating tensile stress will develop small crack-like

defects which may eventually lead to failure of the member, the crack becomes sufficiently large to

cause fracture at the defect location. For structures subject to constant amplitude stress fluctuations,

problems of this nature may be avoided by keeping the cyclic stress below an endurance limit, preventing

the inception of the initial defect. Offshore structures, however, are exposed to a mixture of large and

small stress ranges making this approach impractical. It thus becomes necessary to design the structure

for a desired service life. The method used within FATJACK to carry out the fatigue assessment is based

upon the use of S-N curves.

2.2. S-N Curves

Tests of steel specimens subject to fluctuating loading demonstrate a relationship between the number

of cycles to failure, N, and the applied stress range, S. The form of this relationship is given by:

N = AS-m

where A and m are constants obtained experimentally.

In air, or where corrosion prevention is undertaken, an endurance limit can be identified for constant

amplitude stress cycling below which no fatigue occurs. For variable amplitude stress cycling the cut-

off stress decreases as the fatigue crack grows and this is often allowed for by changing the slope of

the S-N curve below a certain stress level.

Values of A and m are available for a range of typical joints. Values of A and m are available for a range

of typical joints. Many codes of practice provide one or more standard S-N curves, some of which have

been embodied within the FATJACK software.

2.3. Miner's Rule

To account for variable amplitude loading, the S-N curve is supplemented by an additional rule which

permits the fatigue assessment to be undertaken. Miner’s Rule is based upon the concept of fatigue

damage. For a given wave of constant amplitude the damage is given by:



Where many wave cases are being analyzed, the fatigue damage for one wave case with a stress range

Si and a number of cycles ni is:

Miner’s Rule then gives the total annual damage as:

Since the calculation is based upon the number of cycles in a year for the constituent waves, the resulting

damage is that associated with one year of operation. The fatigue life (in years) is, therefore, the recip-

rocal of the damage; that is:

life = 1/D

2.4. Deterministic Methods

Deterministic fatigue methods apply Miner’s Rule directly.

The environmental loading is idealized by representative wave cases, each with a defined number of

loading cycles (or occurrences) in a year. The wave loading is generated (normally using Mechanical

APDL) to produce a series of loadcases which represent the waves for the required number of wave

heights, periods and directions. The structure is then analyzed to determine the stress S for each of the

loadcases and, hence, the fatigue life using Miner’s Rule.

Two analysis approaches are available to undertake a deterministic fatigue assessment.

Under normal circumstances, where the structure responds sinusoidally to the load, the wave loading

generates a loadcase pair for each wave case analyzed. This pair of loadcases represents the real and

imaginary parts of a solution which retains both magnitude and phase information. This is achieved by

undertaking a harmonic wave analysis within Mechanical APDL. This approach is an efficient and effective

way of determining the stress response of the structure to steady state harmonic loading. FATJACK uses

this data to generate the stress ranges directly from the incoming member forces for the loadcase pairs.

This methodology is selected using the ANALYSIS DETERMINISTIC command.

In situations where the structure stress response becomes nonlinear (for example, in shallow water), a

sinusoidal representation may become invalid in which case a more detailed analysis needs to be adopted.

The stress history approach utilizes the stresses resulting from discrete positions for a given wave to



determine explicitly the stress range. In this case Mechanical APDL is used to generate one or more

loadcases for each wave case to adequately define the response of the structure to the applied loading.

If only one loadcase is provided it is assumed to represent the stress amplitude. In this case the stress

range is computed as twice the amplitude. For any other number of loadcases the stress range is

computed as the difference between the maximum and minimum stress occurring within each of the

constituent loadcases forming the wave.

This methodology is selected using the ANALYSIS STRESS HISTORY command.

2.5. Spectral Analysis

When the dynamic response of the structure is important, a more realistic estimate of fatigue life can

be obtained from the spectral method. The damage is accumulated at each inspection point throughout

the frequency range, using the stress response spectrum at that point together with the appropriate

material S-N characteristics.

For the purpose of sea state identification, wave direction is usually classified into eight sectors of 45°

incidence angle bands (Sea states are applied by direction sector scatter diagrams (p. 5)). In each sector,

the occurrence rate of each random sea state, characterized by significant wave height, Hs, and mean

zero crossing period, Tz, is identified as a number on a scatter diagram (A scatter diagram summarizing

the relative occurrence rate of individual sea state conditions for one direction (p. 6)). The ratio of this

number of occurrences to the total for all eight sector scatter diagrams gives the weighting to be applied

later in determining the amount of fatigue damage due to each sea state.

In a particular random sea state, the instantaneous water surface elevation is considered to be caused

by the combined effect of an infinite number of steady state components of wave frequency having

random phase relationships. The amplitude content versus frequency has been shown by practical in-

vestigation to be related to the significant wave height and mean zero crossing period. Using relationships

such as the Jonswap (Ref. 6), Scott-Weigel, Pierson-Moskowitz (Ref. 5) or Ochi-Hubble (Ref. 7) spectra,

each scatter diagram sea state can be reconstituted in terms of water surface elevation components

throughout the frequency range producing sea state spectra, Sηη (See diagram (a) in Random Sea

States (p. 6)).

Figure 2.1 Sea states are applied by direction sector scatter diagrams



Spectral Analysis

Figure 2.2 A scatter diagram summarizing the relative occurrence rate of individual sea

state conditions for one direction

Figure 2.3 Random Sea States

For a given inspection point on the structure, a stress transfer function, σf, is developed by computing

the normalized stress range for each of the constituent waves within a wave incidence sector, the

stresses being normalized by the associated wave heights (See diagram (b) in Random Sea States (p. 6)).

The stress response spectrum for a given sea state, Sσσ, can then be determined by multiplying the

wave spectrum by the square of the associated stress transfer function (See diagram (c) in Random Sea

States (p. 6)).

Thus

Sσσ = Sηη*σ2

f



The fatigue damage incurred from one sea state at one stress inspection point is evaluated using

parameters from its stress response spectrum, the material fatigue data, Miner’s Rule and the relative

rate of occurrence of that sea state, including the assumption that the peak stress levels are distributed

according to a Rayleigh probability distribution (See diagram (d) in Random Sea States (p. 6)).

The damage in one year from each sea state for each inspection point is given by:

The annual damage from each of the sea states is then summed in order to give the total annual

damage from all sea states. The fatigue life is the reciprocal of the total annual damage.

For single slope S-N curves, the damage calculation is undertaken using a gamma function solution

which provides an efficient method for carrying out the integration expression. For multi-linear S-N

curves no such closed form solution exists and the integration has to be undertaken by numerical in-

tegration techniques.

2.6. Time History Methods

The environmental loading is idealized by representative time history cases, each with a defined number

of occurrences in a year. The structural response in the time domain is computed for each required sea

state (normally by a transient analysis) to produce a series of stress time histories. FATJACK reads in the

analysis stress results to create a hot spot stress time history at each inspection location and utilizes

the rainflow counting method to produce a stress range histogram; that is, a table of number of cycles

vs. stress range. The fatigue life is then calculated using Miner’s rule as usual.

2.7. Strategies for Wave Fatigue Analysis

Depending upon the type of fatigue analysis to be undertaken, different ocean loading options are re-

quired before computing fatigue lives in FATJACK. For Mechanical APDL based analyses the following

defines the required data and approach for various types of fatigue analysis:

NotesFATJACK

Analysis

Loading require-

ments

Mechanical

Analysis

Type

Rainflow counting for a

number of ocean environ-

ments

Time HistoryMultiple Stress

Time Histories

Transient Struc-

tural

Time History Dy-

namic

Use multiple load sets to get

a stress range

Stress His-

tory

Individual Stress

Scenarios

Static StructuralTime History De-

terministic Static

Use multiple load steps to

get a stress range

Stress His-

tory

Stress Time HistoryTransient Struc-

tural

Time History De-

terministic Static



Strategies for Wave Fatigue Analysis

NotesFATJACK

Analysis

Loading require-

ments

Mechanical

Analysis

Type

Ocean loading can be gener-

ated using the HROCEAN,

STATIC option

Determinist-

ic

Real & Imaginary

Stresses

Harmonic Re-

sponse

Harmonic Determ-

inistic Static



STATIC option

SpectralReal & Imaginary

Stresses

Harmonic Re-

sponse

Harmonic Spectral

Static



DYNAMIC option

SpectralReal & Imaginary

Stresses

Harmonic Re-

sponse

Harmonic Spectral

Dynamic

The processes involved for various types of fatigue study when using the ANSYS ASAS solver are sum-

marized in Strategies for wave fatigue analysis (p. 8).

Example of a time stress history fatigue analysis (p. 9), Example of a harmonic deterministic fatigue ana-

lysis (static) (p. 10), and Example of steady state dynamic spectral fatigue analysis (p. 11) provide an

overview of the control data required to undertake the different fatigue analyses that are available in

FATJACK. Example of a time history fatigue analysis (p. 12) shows the control data required to undertake

a time history fatigue analysis following a series of transient dynamic analyses.

Figure 2.4 Strategies for wave fatigue analysis using ANSYS ASAS



Figure 2.5 Example of a time stress history fatigue analysis using ANSYS ASAS




Figure 2.6 Example of a harmonic deterministic fatigue analysis (static) using ANSYS ASAS



Figure 2.7 Example of steady state dynamic spectral fatigue analysis using ANSYS ASAS




Figure 2.8 Example of a time history fatigue analysis using ANSYS ASAS

2.8. Parametric SCF Equations



Key:

β = d/D

γ = D/(2T)

τ = t/T

α = L/R

ζ = g/D

D = chord outside diameter = 2R

d = brace outside diameter = 2r

T = chord thickness

t = brace thickness

θ = acute brace to chord angle

L = chord length

g = separation between brace toes (gap)

Table 2.1 Wordsworth Equations For SCFs In T/Y-joints

Validity Range

The following Wordsworth equations are generally valid for joint

parameters within the following limits:

0.13 <= β <= 1.0

12 <= γ <= 32

0.25 <= τ <= 1.0

30° <= θ <= 90

°

8 <= α <= 40



Parametric SCF Equations

Eqn. No.SCF EquationLoad Type

WT1

Axial load

WT2

WT3

In-plane

bending

WT4

Out-of-plane

bending

Brace side

SCFs

Table 2.2 Wordsworth Equations For SCFs In X-joints


WX1

Axial load

WX2

WX3

In-plane

bending

WX4

Out-of-plane

bending (bal-

anced)




Brace side

SCFs

Table 2.3 Wordsworth Equations For SCFs In K-joints


Balanced axi-

al load

WK1

WK2

WK3

WK4

In-plane

bending

Out-of-plane

bending (un-

balanced)

WK5

Brace side

SCF's

Table 2.4 Wordsworth Equations For SCFs In KT-joints


Outer two braces only loaded.Balanced axi-

al loadEquations identical to those given for K joints may be used except that

g is the distance between the toes of the outer braces (gac).





WKT1 In-plane

bending

Unbalanced

out-of-plane

bending

WKT2

WKT3

For brace C replace gab with gbc, θA with θC, θC with θA, βA with βC, βC

with βA and τA with τC.

The above equations were derived with equal sized braces. Caution

should therefore be used when applying the equations to nodes where

there is a large variation in brace dimensions.

Brace load

SCFs

Table 2.5 Kuang Equations In T/Y-joints

Validity Range

The following Kuang equations for T/Y, K and KT joints are

generally valid for joint parameters within the following limits:

0.3 <= β <= 0.8 unless stated otherwise

8.33 <= γ <= 33.3

0.20 <= τ <= 0.8

0° <= θ <= 90

° unless stated otherwise

6.667 <= α <= 40




KT1Axial load

KT2

KT3In-plane

bending

KT4

KT5

KT6

Out-of-plane

bending

KT7

KT8

Table 2.6 Kuang Equations In K-joints


KK1

Axial

load

KK2

KK3

In-plane

bending

KK4

KK5

Out-of-plane

bending

KK6

KK7

KK8




Table 2.7 Kuang Equations In KT-joints


Axial

load

KKT1

KKT2

KKT3

KKT4

In-plane

bending

KKT5

KKT6

Out-of-plane

bending

KKT7

KKT8

KKT9

KKT10

Table 2.8 Kuang Equations In T-joints


Axial load

DT1

DT2




In-plane

bending

DT3

DT4

Out-of-

plane bend-

ing DT5

DT6

Table 2.9 Danish Equations In Y-joints

Validity Range

The following Danish equations for Y, K and KT joints are

generally valid for joint parameters within the following limits:

0.3 <= β <= 0.8

8 <= γ <= 33

0.2 <= τ <= 0.8

0° <= θ <= 90

°

7 <= α <= 40

0.01 <= ζ <= 1.0


The following equations provide the basic SCF formulas for Y

joints. The code permits a reduction to be applied which is

automatically carried out by the program. The actual SCF value

computed is given by:





Axial load

DY1

DY2

In-plane

bending

DY3

DY4

DY5

Out-of-plane

bending

DY6

DY7

DY8

Table 2.10 Danish Equations In K and KT-joints


The following equations provide the basic SCF formulas for K and KT

joints. The code permits a reduction to be applied which is automatic-

ally carried out by the program. The actual SCF value computed is

given by:

Axial load K-

joints

DK1

DK2




Axial load

KT-joints

DKT1

DKT2

DKT3

In-plane

bending

DK3

DK4

Out-of-plane

bending

Table 2.11 Danish Equations In X-joints

Validity Range

The following Danish equations for X joints are generally valid

for joint parameters within the following limits:

0.13 <= β <= 0.95

12 <= γ <= 32

0.25 <= τ <= 1.0

30° <= θ <= 90

°

8 <= α <= 40


Axial load

DX1

DX2





In-plane

bending

DX3

DX4

Out-of-plane

bending

DX5

DX6

Table 2.12 Efthymiou Equations For SCFs In T/Y-joints

Validity Range

The following Efthymiou equations for T/Y joints are generally

valid for joint parameters within the following limits:

0.25 <= β <= 1.0

8 <= γ <= 32

0.25 <= τ <= 1.0

20° <= θ <= 90

°

4 <= α <= 40

-0.6β/sin θ <= ζ <= 1.0

Short

Chord Cor-

rection

Eqn.

No.

SCF EquationLoad Type

If C < 0.8ET5

Axial load -

general fixity

conditions F1 else F2

None

If C < 0.8

F1 else F2

None

ET6

ET3

ET7



Short

Chord Cor-

rection

Eqn.

No.


NoneET8

In-plane

bending

None ET9

F3ET10

Out-of-plane

bending

F3 ET11

Chord-end fixity parameterShort chord correction factors (α < 12)

Table 2.13 Efthymiou Equations For SCFs In X-joints

Short Chord

Correction

Eqn.

No.


If C < 0.8EX1

Axial load

F1 else F2

None

If C < 0.8

F1 else F2

None

EX2

EX3

EX4

None

In-plane

bending

None

F3EX5

Out-of-plane

bending

F3EX6




Table 2.14 Efthymiou Equations For SCFs In Gap/Overlap K-joints

Short Chord

Correction

Eqn.

No.


Balanced axial

load

None

None

EK1

EK2

Unbalanced

in-plane

bending

EK3

Unbalanced

out-of-plane

bending F4

F4

EK4

EK5

[ET10]A is the chord SCF adjacent to brace A as estimated from eqn ET10.



Note that the designation of braces A and B is not geometry-dependent, it is nominated by the user.

Table 2.15 Efthymiou Equations For SCFs In KT-joints

Short Chord

Correction

Eqn.

No.


Balanced axial

load

In-plane

bending

Out-of-plane

bending

F4

F4

EKT1

EKT2




Table 2.16 Efthymiou Equations For SCFs In X-joints For Use In Influence Function

Calculations

Short Chord

Correction

Eqn.

No.


If C < 0.8EX7

Axial load on

reference

brace only F1 else F2

If C < 0.8

F1 else F2

EX8

F3

Out-of-plane

bending on

reference

brace only F3

Table 2.17 Efthymiou Influence Functions For X-joints

Eqn. No.Influence function for reference braceLoad Type

Axial load

EIX1

EIX2

EIX3

EIX4

Out-of-plane

bending

EIX5

EIX6



Note that in the above expressions subscript A refers to the reference brace, subscript B to the interacting

brace under consideration.

Table 2.18 Efthymiou Equations For SCFs In Gap/Overlap K-joints For Use In Influence

Function Calculations

Short Chord

Correction

Eqn.

No.


If C < 0.8 F1 else F2

Axial load on

one brace

only

None

If C < 0.8 F1 else F2

None

If no braces are present on the opposite side of the chord,

βm = 0

None

In-plane

bending on

one brace

only

None

Out-of-plane

bending on

one brace

only

F3

F3

EK6

EK7






Table 2.19 Efthymiou Influence Functions For K-joints

Eqn. No.Influence function for brace ALoad Type

Axial load

EIK1

EIK2

EIK3

EIK4

Out-of-plane

bending

EIK5

EIK6

Eqn. No.Influence function for brace ALoad Type

Axial load

EIK1

EIK2

EIK3

EIK4

Out-of-plane

bending

EIK5

EIK6





Table 2.20 Efthymiou Equations For SCFs in KT-joints For Use In Influence Function

Calculations


Axial load on

reference

brace only

Out-of-plane

bending on

reference

brace only

EKT3

EKT4


Axial load on

reference

brace only





Out-of-plane

bending on

reference

brace only

EKT3

EKT4



Table 2.21 Efthymiou Influence Functions For KT-joints

Eqn. No.Influence function for brace ALoad

Type

Axial

EIKT1

EIKT2

EIKT3

EIKT4




Table 2.22 Efthymiou Hot-Spot Stresses In KT-joints

Eqn. No.Hot spot stress expressionLoad Type

Out-of-

plane

bending EIKT5

EIKT6



Chapter 3: FATJACK Analysis Methods


3.1. Overview

3.2. Environmental Information

3.3. Joint Selection

3.4. Joint Classification

3.5. Inspection Points

3.6. Design Information

3.7. Stress Concentration Factors

3.8. S-N Curves

3.9. Units

3.10. Element Cross Sections

3.11. Results presentation

3.1. Overview

Fatigue analyses can require large amounts of data due to the methods employed in determining the

hot spot stresses from the nominal brace loads. In addition, the mathematical model is often greatly

simplified especially at joints where brace centre-lines are assumed to pass through a common point

and where stub and/or can details have been omitted.

FATJACK includes an extensive command set which enables the user to automatically generate much

of the required data and provides methods for developing a more precise definition of the problem

than can be obtained from the analysis model.

3.2. Environmental Information

Fatigue analyses require information about the wave loading used to develop the analytical results that

are to be processed. FATJACK requires that wave height, period and direction are supplied for each

wave case that has been analyzed. For stress history analyses, it is also necessary for the program to

know how many wave positions have been used for each wave case (see Deterministic Methods (p. 4)).

Provided that the environmental wave loading has been generated using the ocean definition in

Mechanical APDL, FATJACK can automatically extract the wave information from the analysis database

files. It should be noted, however, that this facility is not available if the loading has been modified in

any way. In these cases the wave information must be supplied as part of the FATJACK input data.

3.3. Joint Selection

FATJACK allows selective processing of one or more individual joints in the model. This permits specific

areas of a model to be examined with local changes in design information.

The joints may either be listed explicitly or using the keyword ALL to request that every joint which

has valid elements connected is to be processed. Only BEAM and TUBE elements will be used by FATJACK,

all other element types will be ignored.



Joints are usually represented by a single node, to which the brace and chord elements are attached.

It is sometimes necessary to model the physical separation of work points in a joint by the use of 2 or

3 nodes.

This is achieved using a combination of CHORD and TYPE commands. In these cases one of the nodes

is designated as the joint node and this is used when referring to any properties regarding that joint.

3.4. Joint Classification

By default FATJACK utilizes the configuration of the brace members incident at a joint to determine

the joint classification used for computing stress concentration factors for the brace connections to the

joint.

Unless otherwise defined (by using the CHORD command) the chord at a given joint is selected based

upon the connecting members with the largest diameter. Where several members have the same dia-

meter, the elements with the largest thickness are adopted. In certain circumstances this process will

not produce a unique chord definition; for example, at X joints with similar members, in which case the

chord specification is compulsory. It should also be noted that where the chord elements are determined

by the program the chord length required for the stress concentration factor (SCF) calculations will be

computed as 2/3 times the combined lengths of the selected elements. This will produce erroneous

SCFs if the chord elements selected do not completely define the chord member; for example, where

intermediate nodes have been included. Either all the elements which constitute the chord should be

defined, or an explicit chord length should be given, using the CHORD command.

The remaining members at a joint, considered to be brace members, are then separated into groups

of elements that are in the same chord-brace plane. Within each plane a joint configuration is identified

for each brace end using the following classification table:

ClassificationNfarNnear

T/Y01

X11

T/Y21

T/Y31

Kany2

KTany3



Notes

1. Nnear is the number of braces on the same side of the chord as the brace under consideration (including

the brace under consideration).

2. Nfar is the number of braces on the far side of the chord with respect to the brace under consideration.

3. If the angle subtended with the chord is 90o±5

o then the reference brace is designated as a T, otherwise

the joint is classified as a Y.

If the user wishes to assign joint classifications other than that provided by the program this can be

achieved by using TYPE commands for the joint/brace combinations concerned. Note that TYPE com-

mands are ignored if using influence functions since this relies on a knowledge of all braces at a joint.

3.5. Inspection Points

Results from FATJACK are reported at one or more inspection points for braces connected to selected

joints. The location of the inspection points for braces are identified by an angle for tubular sections,

or a pair of ordinates for non-tubular braces. The reference point from which the angles or ordinates

are measured depends upon the type of joint being examined.

3.5.1. Tubular Joint Inspection Points

Where a joint consists of a chord together with associated braces the inspection point angle is measured

relative to a saddle location as shown below:

The member local reference x axis is defined as being along the member concerned and is always ori-

entated away from the joint. The local reference y axis is in the same direction as the member local

reference y axis. The local reference z axis forms a right handed set with the member axis and the local

reference y axis. Note that, for consistency, the results are reported in terms of brace in-plane (y local

axis) and out-of-plane (z local axis) bending.

3.5.2. Tubular Butt Joints

Where a joint has no identifiable chord the program adopts a reference system that relates to the

members connected to the joint. This is shown diagrammatically below:



Inspection Points

The member local reference x axis is defined as being along the member concerned and is always ori-

entated away from the joint. The local reference y axis is in the same direction as the member local

reference y axis. The local reference z axis forms a right handed set with the member axis and the local

reference y axis. Note that, for consistency, the results are reported in terms of brace in-plane (y local

axis) and out-of-plane (z local axis) bending.

3.5.3. Non-Tubular Braces

Non-tubular joints have no associated chord elements and are thus treated in a similar manner to tubular

butt joints. The inspection points are then defined by way of y and z ordinates (or in-plane bending

and out-of-plane bending ordinates to be strictly consistent).

The member local reference x axis is defined as being along the brace concerned and is always orientated

away from the joint. The in-plane axis is in the same direction as the brace local y axis. The out-of-plane

axis forms a right handed set with the brace axis and the in-plane axis.



3.6. Design Information

By default FATJACK utilizes the geometric and topology information that is stored in the ASAS fatigue

model backing files. This information is used for computing both stress values and stress concentration

factors (where requested).

There may be many instances when the data utilized for the structural analysis is inconsistent with that

required to undertake the fatigue study and FATJACK provides several mechanisms to override the

values that would be adopted by default.

3.6.1. Design Geometry

The geometry information (diameter, thickness, areas, etc) is used both for the SCF computations and

stress evaluation. The default information extracted from the analysis backing files may be overridden

(or augmented) by utilizing the DESIGN command which enables both the section type and properties

to be defined. For non-tubular sections this is essential if sections have not been utilized in the original

analysis in order that the appropriate SCF values may be utilized (see Stress Concentration Factors (p. 37)).

3.6.2. Secondary Elements

Since FATJACK is joint based, all valid elements connected to a joint will be processed. There may be

situations where certain elements are not required for fatigue processing and these may be selectively

deactivated by defining them as secondary elements. Note that the secondary elements are effectively

removed from the joint and thus will not be included in the joint classification and, hence, any automatic

SCF evaluation that may be requested. Similarly secondary members will not be included in any influence

function computations where this is operative (see Influence Functions (p. 38)).

3.7. Stress Concentration Factors

The damage calculations required for a fatigue analysis utilize the hot spot stresses at the inspection

points defined for a given brace. These hot spot stresses are normally determined from the brace

nominal loads (axial force and lateral bending) and associated stress concentration factors for the locations

concerned.

The stress concentration factors (SCFs) may be provided in one or two ways:

• Explicit SCF definitions

• Utilizing built-in empirical formulations to automatically generate the required SCF values.

An alternative approach to conventional SCF evaluation of hot spot stresses is the use of so-called in-

fluence functions which account for the load distribution at a joint. This method can be requested when

using the Efthymiou equations by including the INFL option.

3.7.1. Explicit SCF Definitions

Where SCF values are known explicitly these may be provided in a number of ways:

• For tubular sections use:

SCFJ if crown and saddle SCF values are known; for example, if generated by empirical formulae

by the user.

SCFA if SCF values are known at specific locations; for example, results of a detailed finite element

joint analysis, or from model tests.



Stress Concentration Factors

• For non-tubular sections use:

SCFB if the SCF values are constant across the section.

SCFP if the SCF values vary according to location.

For all section types a default value may be defined which is associated with a brace element in the

absence of any explicit definitions or computed SCF values. Note that default SCF values are associated

with a section profile (WF, BOX, etc) rather than an element type (BEAM, TUBE).

3.7.2. Empirical SCF Formulations

FATJACK incorporates automatic SCF generation facilities for tubular joints, based upon the following

empirical formulations:

• Wordsworth (Ref. 2)

• Kuang (Ref. 3)

• DS449 (Ref. 10)

• Efthymiou (Ref. 11)

These formulations provide SCF values which depend upon the joint classification, load condition, and

position around the brace/chord interface.

This facility enables brace elements at a joint to have SCF values computed at the crown and saddle

locations. To provide increased flexibility in the application of empirical formulae to SCF calculations,

FATJACK includes the ability to utilize different formulations for specific SCF values around a given

brace member. This is achieved by specifying an equation matrix, the constituents of which define the

formula to be adopted for each of the loading components and position. The user can thus utilize the

most appropriate formulations for a given joint type as required by many certification authorities.

Automatic generation of SCF values is requested using the SCF AUTO commands. To provide total

flexibility in the determination of the SCF values, parameter definitions and limits may be modified using

the PARAMETER and LIMIT commands.

The brace side SCF values obtained from the Kuang equations may be modified using the Marshall

Reduction factor if required using the REDUCTION command.

In addition, minimum SCF values may be specified, to provide a lower bound for any computed SCF,

using the SCFM command.

3.7.3. Influence Functions

Conventional SCF formulations assume a certain loading condition in determining the SCF values viz:

• Axial loads in K, KT and X joints are assumed balanced

• Out-of-plane bending in K and KT joints is assumed unbalanced

• Out-of-plane bending in X joints is assumed balanced

• In-plane bending in K joints is assumed balanced

For simple joints in a framed structure these assumptions are often reasonably valid and will provide

good estimates of the structural behavior. For more complex joints, however, the load paths become

much more ill-defined and it is not possible to easily determine their effects on the hot spot stresses.



The influence function approach automatically accounts for load dependency by not only computing

SCF values which are multiplied by the reference brace, but also generating influence terms which are

multiplied by loading in adjacent braces at the joint in question. The key principle involved in this

methodology is the superposition of linear elastic stress fields which enables a hot spot stress to be

computed from the sum of the contributions from all braces at a joint.

The influence functions derived by Efthymiou (Ref. 11) have been incorporated into FATJACK and are

utilized by including the INFL option in the preliminary data (without this option the conventional SCF

values are computed). At present only planar braces are considered in the influence function computa-

tions, the multiplanar effects considered as being small by comparison.

Note that the SCFM command has no effect on computed influence functions.

For any joints where the Efthymiou equations cannot be (or are not) applied, conventional SCF values

are computed (if requested). It is not currently possible to mix conventional SCFs (either explicitly

defined or computed) with influence functions for a given joint.

3.7.4. SCF Interpolation

Where SCF values are given for the crown and saddle locations, intermediate SCFs are developed by

interpolating the defined values. At present linear interpolation is used.

Note that this normally requires that a non-zero SCF term is given for the in-plane bending term at the

saddle, and the out-of-plane bending term at the crown. For automatically generated terms the following

convention is adopted:

SCFips = SCFipc

SCFopc = SCFops

where:

ips

in-plane bending saddle

ipc

in-plane bending crown

opc

out-of-plane bending crown

ops

out-of-plane bending saddle



Stress Concentration Factors

3.7.5. Annotated SCF File Generation

Since FATJACK is joint based, all valid elements connected to a joint will be processed. There may be

situations where certain elements are not required for fatigue processing and these may be selectively

deactivated by defining them as secondary elements. Note that the secondary elements are effectively

removed from the joint and thus will not be included in the joint classification and, hence, any automatic

SCF evaluation that may be requested. Similarly secondary members will not be included in any influence

function computations where this is operative (see Influence Functions (p. 38)).

Example 3.1 Example Generated SCF File

** JOINT 1420* CHORD 1001* CONNECTING BRACES 151 1101*SCFJ 1420 151 BRAC 7.23 7.23 3.78 3.78 10.47 10.47 * K JOINT E E E E E ESCFJ 1420 151 CHOR 9.15 9.15 4.44 4.44 13.04 13.04 * E E E E E ESCFJ 1420 1101 BRAC 2.40 2.40 2.89 2.89 5.58 5.58 * K JOINT E E E E E ESCFJ 1420 1101 CHOR 3.81 3.81 2.40 2.40 6.95 6.95 * E E E E E E** JOINT 1520* CHORD 1005* CONNECTING BRACES 141 152 122 121*SCFJ 1520 141 BRAC 2.15 15.82 4.05 4.05 12.33 12.33 * T JOINT E E E E E ESCFJ 1520 141 CHOR 5.65 24.07 5.41 5.41 17.33 17.33 * E E E E E ESCFJ 1520 152 BRAC 2.05 13.90 3.78 3.78 10.95 10.95 * Y JOINT E E E E E ESCFJ 1520 152 CHOR 4.51 18.56 4.44 4.44 13.64 13.64 * E E E E E ESCFJ 1520 122 BRAC 1.41 27.97 4.67 4.67 16.99 16.99 * X JOINT E= E+ E+ E+ E+ E+SCFJ 1520 122 CHOR 5.42 71.29 9.20 9.20 37.25 37.25 * E+ E+ E+ E+ E+ E+SCFJ 1520 121 BRAC 1.41 27.97 4.67 4.67 16.99 16.99 * X JOINT E= E+ E+ E+ E+ E+SCFJ 1520 121 CHOR 5.42 71.29 9.20 9.20 37.25 37.25 * E+ E+ E+ E+ E+ E+** JOINT 2330* CHORD 0* CONNECTING BRACES 906 905 225 226 205*SCFJ 2330 906 BRAC 1.00 1.00 1.00 1.00 1.00 1.00 * UN JOINTSCFJ 2330 906 CHOR 1.00 1.00 1.00 1.00 1.00 1.00 *SCFJ 2330 905 BRAC 1.00 1.00 1.00 1.00 1.00 1.00 * UN JOINTSCFJ 2330 905 CHOR 1.00 1.00 1.00 1.00 1.00 1.00 *SCFJ 2330 225 BRAC 1.00 1.00 1.00 1.00 1.00 1.00 * UN JOINTSCFJ 2330 225 CHOR 1.00 1.00 1.00 1.00 1.00 1.00 *SCFJ 2330 226 BRAC 1.00 1.00 1.00 1.00 1.00 1.00 * UN JOINTSCFJ 2330 226 CHOR 1.00 1.00 1.00 1.00 1.00 1.00 *SCFJ 2330 205 BRAC 1.00 1.00 1.00 1.00 1.00 1.00 * UNJOINTSCFJ 2330 205 CHOR 1.00 1.00 1.00 1.00 1.00 1.00 *

The annotation after each SCFJ command corresponds to the following convention:

equation (6)joint type*a

scf values (6)SCFJ joint brace BRAC

equation (6)*a

scf values (6)SCFJ joint brace CHOR

aequation (6)



where equation (i) is the requested empirical formulation identifier (W, K, D, E) for the printed scf value

(i).

The equation (i) is optionally followed by + or =. If + is printed this signifies that one or more parameters

were exceeded for the given location and the value corresponding to the computed parameters are

reported. If = is printed this signifies that one or more parameters were exceeded for the given location,

and the value corresponding to the limiting parameters are reported.

3.8. S-N Curves

S-N curves relate stress range information (S) to number of cycles to failure (N). Basic design curves

consist of linear or bi-linear relationships between log (S) and log (N). FATJACK enables S-N data to be

defined by reference to a library of S-N design curves from various recognized sources viz:

Department of Energy T curve

Department of Energy F2 curve

American Petroleum Institute X curve

American Petroleum Institute X’ curve

Danish Standard DS449 tubular joint curve

Other curves may be defined explicitly by providing an ordinate on the curve and associated slope.

Multi-linear curves are supported, as are curves with a cut-off stress below which no damage occurs.

Thickness correction may be applied to the S-N curves to account for varying plate thickness. This cor-

rection (requested using the THIC command) has the effect of shifting the S-N curves to reduce the fatigue

strength with increasing thickness. The correction makes

3.9. Units

FATJACK requires that UNITS are defined for any dimensional input data to FATJACK itself.

Note, however, that the geometric angular data unit defaults to degrees, and wave frequencies are always

defined in Hertz.

The user must ensure that they are consistent with the units adopted in the structural model.

If local modified input data units are required, this is achieved by specifying one or more UNITS com-

mands within the main body of the FATJACK data thus permitting a combination of unit systems

within the one data file (see UNITS command).

The results units cannot be modified since they are dimensionless or are in non-standard units.

3.10. Element Cross Sections

Any design data provided (using the DESI command) will overwrite the section information. Likewise,

for non-tubular sections, use of the INSP SYMM, INSP POSN or SCFPOINT commands will replace the

section data.

3.11. Results presentation

The type and format of the results to be presented is determined using the PRINT command. A number

of options exist that permit a wide variety of information to be reported with as much or as little detail

as required.



Results presentation


Chapter 4: FATJACK Command Reference

The data for FATJACK consists of a set of commands which indicate the type of calculation to be per-

formed and the content of the output. The basic data structure is as follows:

Except for stress and time history calculations, FATJACK expects each load condition to consist of a pair

of loadcases representing the real and imaginary parts of the applied cyclic loading. Mechanical APDL

automatically outputs pairs of loadcases if the harmonic option is selected. The term wave case is used

in the FATJACK data description to indicate which pair of cases is being referred to. For example, wave

case 2 refers to the 2nd wave analyzed using the harmonic option or the 3rd and 4th loadcase from a

static analysis.

For stress history analyses a wave case may generate any number of loadcases. For time history analyses,

a wave history case refers to the analysis results obtained for a specific wave condition. The details of

the commands required for each analysis type are given in the following sections.

4.1. FATJACK Free Format Syntax


4.1.1. General Description

4.1.2. Special Symbols

4.1.1. General Description

The input data for FATJACK are specified according to syntax diagrams similar to that shown below.

The conventions adopted are described in the following pages. Detailed descriptions of each of the

data items can be found in the remainder of this chapter.

Each data item consists as follows



Each horizontal branch represents a possible input instruction. Input instructions are composed of

keywords (shown in UPPER-CASE), numerical values or alphanumerics (shown in lower-case) and

special symbols. Each item in the list is separated from each other by a comma or one or more blank

spaces.

An input line must not be longer than 80 characters.

Numerical values have to be given in one of two forms:

i. If an integer is specified, a decimal point must not be supplied.

ii. If a real value is specified, the decimal point may be omitted if the value is a whole number.

Exponent formats may be utilized where real numbers are required. For example, the following are

equivalent:

• 0.004

• 4.0E-3

• 4.0D-3

Similarly, the following have the same value:

• 410.0

• 410

• 4.10E2

Alphanumerics are any non-numeric strings, which may include the letters A-Z, numbers 0-9, and the

characters +, -, / and :. The letters A-Z may be supplied in either uppercase or lowercase, but no distinc-

tion is made between the uppercase and lowercase form. Hence “A” is assumed identical with “a”, “B”

with “b” and so on. For example, the following are all permissible alphanumeric strings:

• CASE

• STR1 END

• 3mm

Similarly, the following are all identical strings:

• COMB

• Comb

• comb

Alphanumeric strings must not include any special symbols (See Special Symbols (p. 45)).

If certain lines are optional, these are shown by an arrow which bypasses the line(s):



In order to build up a block of data, a line or a series of lines may need to be repeated until the complete

set has been defined. This is shown by an arrow which loops back:

If certain data items within a command line are optional, these are shown by an arrow which bypasses

the appropriate item:

Some data lines require an integer or real list to be input whose length is variable. This is shown by a

horizontal arrow around the list variable(s):

Where one or more possible alternative items may appear in the list, these are shown by separate

branches for each:

4.1.2. Special Symbols

The following is a list of characters which have a special significance to the FATJACK input:

An asterisk is used to define the beginning of a comment, whatever follows on the line

will not be interpreted. It may appear anywhere on the line, any preceding data will be

processed as normal. For example:

*

* THIS IS A COMMENT FOR THE WHOLE LINE

CASE 4 2.7 * THIS IS A COMMENT FOR PART OF A LINE



FATJACK Free Format Syntax

Single quotes are used to enclose some text strings which could contain otherwise inad-

missible characters.The quotes are placed at each end of the string.They may also be

used to provide in-line comments between data items on a given line. For example:

STRUCTURE ’As used for design study’ STRU

'

A comma or one or more consecutive blanks will act as a delimiter between items in the

line.

For example, 5, 10, 15 is the same as 5 10 15

,

Note that two commas together signify that an item has been omitted. This may

be permissible for certain data blocks.

For example: 5,, 15 is the same as 5 0 15

Unless otherwise stated in the section describing the data block, omitted numer-

ical values are zero.

A colon at the start of the line signifies that the line is a continuation from the previous

line.

For example

:

5

: 10

: 15

is the same as 5 10 15

A command @filename may appear anywhere in a data file.When such a command is

encountered, the input of data switches to the file filename and data continues to be

@

read from that file until either the end-of-file is reached or an @ command is encountered

in the secondary file.

When the end of the secondary file is reached, that file is closed and input

switches back to the previous data file. If, however, an @ command is found in

the secondary file, input switches to yet another file. This process can continue

until a maximum of 5 secondary files are open simultaneously.

For example

@prelim.dat

@wave.dat

@design.dat

@scf.dat

@spectral.dat

design.dat might then contain the lines

@type.dat

@desi.dat

@gap.dat

@chord.dat

finally



type.dat contains the joint designation data

desi.dat contains the design geometry data

etc

4.2. FATJACK Priority of Data Assignments

There are a number of commands that allow element and element ‘step’ data to be assigned in terms

of element, group or property numbers. These appear in the command syntax diagrams in the following

format:

The priority of such assignments is defined below:

• Element data - use element data assigned to individual elements (ELEM)

– if none - use element data assigned to the group the element belongs to (GROU)

→ if none - use element data assigned to the property integer used by the element (PROP)

• if none - no element data assigned to element.

• Step data - use step data assigned to individual elements (ELEM)

– if none - use step data assigned to the group the element belongs to (GROU)

→ if none - use step data assigned to the property integer used by the element (PROP)

• if none - use element data assigned to individual elements (ELEM)

– if none - use element data assigned to the group the element belongs to (GROU)

→ if none - use element data assigned to the property integer used by the element (PROP)

• if none - no step data assigned to element.

Element and step data assignment is not order dependant. This is demonstrated by the following example:

COMMand .... data1 ELEM 1COMMand .... data2 GROU 5COMMand .... data3 ELEM 2COMMand .... data4 PROP 1

Assuming elements 1 and 2 are in group 5:

• Element 1 has data1 assigned

• Element 2 has data3 assigned

• All other elements in group 5 have data 2 assigned

• All elements with property integer 1, except elements 1 and 2 and elements in group 5, have data4

assigned.

It should be noted that when step data is explicitly being defined it overrides any element assignments

even if the step data is assigned to a group or property and the element data assigned to an individual

element. Thus in the following example:

COMMand .... data1 STEP 2 GROU 5COMMand .... data2 STEP 2 PROP 1



FATJACK Priority of Data Assignments

COMMand .... data3 ELEM 1COMMand .... data4 STEP 2 ELEM 2

Step 2 of element 1 has data1 assigned because the group assignment overrides the property assignment.

In this instance the step specific group assignment also overrides the element assignment which is not

step specific.

• Step 2 of element 2 has data4 assigned.

• Step 2 of all other elements in group 5 have data1 assigned.

• Step 2 of all elements with property integer 1, except those in group 5, have data2 assigned.

• All steps, except step 2, of element 1 have data3 assigned.

• No data is assigned to any steps, other than step 2, for any elements other than element 1.

Note also that if a command is assigned more than once to a given element, group or property, a

warning will be issued and the last defined value, or values, adopted.

4.3. Preliminary Data

The preliminary data is the first block of the FATJACK data. It defines the memory size to be used, the

project name, structure and component names, file names and options to be used. It also defines which

files are to be saved for further processing.



The preliminary data must contain at least a JOB, STRUCTURE and END command. Other commands

should be used as appropriate.

4.4. Fatigue Analysis method


4.4.1. ANALYSIS command

4.4.2. Deterministic Analysis

4.4.3. Spectral Analysis

4.4.4. Stress History Analysis

4.4.5.Time History Analysis

4.4.1. ANALYSIS command

The ANALYSIS command selects the method of analysis to be utilized. This command must immediately

follow the preliminary data.



Fatigue Analysis method

Parameters

ANALYSIS

Keyword

DETERMINISTIC

Keyword to select a deterministic analysis.

SPECTRAL

Keyword to select a spectral fatigue analysis.

STRESS HISTORY

Keyword to select a stress history analysis.

Notes

1. One of these analysis type keywords must appear as the first line after the preliminary data.

2. The analysis type determines the valid commands that may be utilized within the input data file. The

following sections Deterministic Analysis (p. 50) to Time History Analysis (p. 62) summarize the available

commands for each type of analysis.

Examples

ANALYSIS SPECTRALANALYSIS STRESS

4.4.2. Deterministic Analysis

This type of analysis requires two sets of data:

• Target fatigue life (YEAR). Computed lives below this figure will be reported as having failed.

• Wave occurrence data in the form of number of occurrences per year (DETE). This data may either ex-

plicitly reference waves that have been analyzed; that is, referred to in the WAVE data, or may consist

of wave height occurrences, in which case interpolation is carried out to obtain member forces for wave

heights that have not been analyzed. This second approach permits a limited number of waves to be

structurally analyzed whilst providing a much more detailed fatigue definition.

Deterministic Commands

NoteUsageDescriptionCommand

CSelects deterministic analysis methodANALYSIS DE-

TERMINISTIC

CSelects joints at which fatigue lives are calcu-

lated

JOINT

1CSpecifies wave information from analysisWAVE




2Chord elements at a jointCHORD

Modified section properties for elementsDESIGN

Gap dimensions for specific braces at a jointGAP

Default gap dimensionGAPDEFAULT

Inset distance for moment backoffINSET

Secondary elements to be ignored in checksSECONDARY

Joint definition and classificationTYPE

Inspection point selectionINSPECTION

SCF empirical equation limits modificationLIMITS

SCF empirical parameter modificationPARAMETER

3Requests Marshall ReductionREDUCTION

4CDefault SCF valueSCF TUB DE-

FAULT4CDefault SCF value

SCF RHS DE-

FAULT 4

4

C

C

Default SCF value

Default SCF valueSCF WF DE-

FAULT

SCF BOX DE-

FAULT

Default SCF equations to be used in genera-

tion

SCF AUTO

DEFAULT

SCF equations to be used at specific jointsSCF AUTO

JOINT

SCF values at specific inspection points on

tubular braces

SCFANGLE

User defined SCF values for non-tubular

braces

SCFBRACE

User defined saddle and crown SCFsSCFJOINT

Minimum SCF valuesSCFMINIMUM

SCF values at specific inspection points on

non-tubular braces

SCFPOINT

Requests S-N thickness correctionTHICKNESS

User defined S-N damage curve definitionCURVE

CWave occurrence dataDETE

CS-N curve assignmentS-N

CTarget fatigue lifeYEAR

5Report optionsPRINT

CTerminates data inputSTOP

Usage




C

Compulsory command, but see notes below where applicable.

Notes

1. This data can be generated by FATJACK using the WAVE AUTO command provided the wave loading

was generated using the Mechanical application.

2. Whilst not compulsory it is recommended that a default gap is specified. In the absence of such a

command, braces forming a K or KT configuration will have the gap computed unless specific GAP

data is supplied. This may result in incorrect SCF calculations at joints with simplified modelling.

3. The Marshall Reduction factor is only applicable to SCF values generated using the Kuang equations.

4. The SCF DEFAULT command must be supplied for each section type that is to be processed.

5. In the absence of a PRINT command a detailed report will be produced.

4.4.2.1. Deterministic Analysis Example

The data has the following characteristics:

• New structure defined

• Time history results retrieved from multiple structures

• Time history occurrence specified with probabilities

• Stress range intervals for cycle counting computed automatically

Example 4.1 Example of Deterministic Analysis Data File

SYSTEM DATA AREA 200000PROJECT FATDJOB POSTFILES JACDSTRUCTURE JACDTITLE FATJACK USER MANUAL EXAMPLEOPTIONS GOON NODL NOBL PRNOUNITS KN MENDANALYSIS DETERMINISTICSCF TUBE DEFA 1.0 1.0 1.0 1.0 1.0 1.0*USE GENERIC DEFINITION FOR SCF EQUATIONSSCF AUTO JOINT EFTHYMIOU: 1110 2210 1120 1210 1520 2130 1420 1130 1540 1140 1150 1440: 1310 1350 2330 1330 2520 2540 2110 2120 3130 3210 2420 2140 2150 2440 3250: 2310 2350 3350 3310 3420 3440 3110 3120 4130 3520 4210 3540 3140 3150 4250: 3330 4330 4110 4150 4310 4350 2250 1250WAVE AUTO*THE FOLLOWING JOINTS ARE CONNECTED TO AN ELEMENTJOIN 1110 2210 1120 1210 1520 2130 1420 1130 1540 1140 1150 1440 1250 2250: 1310 1350 2330 1330 2520 2540 2110 2120 3130 3210 2420 2140 2150 2440 3250: 2310 2350 3350 3310 3420 3440 3110 3120 4130 3520 4210 3540 3140 3150 4250: 3330 4330 4110 4150 4310 4350SECO ELEM 1505 1506 1509 504 1510 503 514 513 524 523 1401 825 1201 1203 827: 1402 1204 1501 1202 1502 1503 1504**EXPLICIT DEFINITION OF K JOINT AND ASSOCIATED CHORDCHORD 1330 105 106 LENGTH 20.0 FIX 0.7TYPE 1330 K 125 126GAP1330125 126 -0.03 THRU 125*USER DEFINED SN CURVE WITH THICKNESS CORRECTION, REQUIRES BASE THICKNESS*TO BE SPECIFIEDUNITS N MMCURV USR1 MULT 45.0 1.0E7 3.56: 45.0 1.0E7 4.56



: THICK 20.0S-N USR1 ELEM ALLTHICKUNITS KN MDETE HEIGHT 699458 1.0 0.0 DAF 1.6DETE HEIGHT 685279 1.0 45.0 DAF 1.6DETE HEIGHT 615024 1.0 90.0 DAF 1.6DETE HEIGHT 568370 1.0 135.0 DAF 1.6DETE HEIGHT 180369 2.0 0.0 DAF 1.5DETE HEIGHT 167805 2.0 45.0 DAF 1.5DETE HEIGHT 167650 2.0 90.0 DAF 1.5DETE HEIGHT 156061 2.0 135.0 DAF 1.5DETE HEIGHT 46512 3.0 0.0 DAF 1.45DETE HEIGHT 41091 3.0 45.0 DAF 1.45DETE HEIGHT 45700 3.0 90.0 DAF 1.45DETE HEIGHT 42851 3.0 135.0 DAF 1.45DETE HEIGHT 11994 4.0 0.0 DAF 1.38DETE HEIGHT 10062 4.0 45.0 DAF 1.38DETE HEIGHT 12458 4.0 90.0 DAF 1.38DETE HEIGHT 11766 4.0 135.0 DAF 1.38DETE HEIGHT 3093 5.0 0.0 DAF 1.32DETE HEIGHT 2464 5.0 45.0 DAF 1.32DETE HEIGHT 3396 5.0 90.0 DAF 1.32DETE HEIGHT 3231 5.0 135.0 DAF 1.32DETE HEIGHT 798 6.0 0.0 DAF 1.25DETE HEIGHT 603 6.0 45.0 DAF 1.25DETE HEIGHT 926 6.0 90.0 DAF 1.25DETE HEIGHT 887 6.0 135.0 DAF 1.25DETE HEIGHT 206 7.0 0.0 DAF 1.2DETE HEIGHT 148 7.0 45.0 DAF 1.2DETE HEIGHT 252 7.0 90.0 DAF 1.2DETE HEIGHT 244 7.0 135.0 DAF 1.2DETE HEIGHT 53 8.0 0.0 DAF 1.15DETE HEIGHT 36 8.0 45.0 DAF 1.15DETE HEIGHT 69 8.0 90.0 DAF 1.15DETE HEIGHT 67 8.0 135.0 DAF 1.15DETE HEIGHT 14 9.0 0.0 DAF 1.10DETE HEIGHT 9 9.0 45.0 DAF 1.10DETE HEIGHT 19 9.0 90.0 DAF 1.10DETE HEIGHT 18 9.0 135.0 DAF 1.10DETE HEIGHT 4 10.0 0.0 DAF 1.05DETE HEIGHT 2 10.0 45.0 DAF 1.05DETE HEIGHT 5 10.0 90.0 DAF 1.05DETE HEIGHT 5 10.0 135.0 DAF 1.05DETE HEIGHT 1 11.0 0.0 DAF 1.01DETE HEIGHT 1 11.0 45.0 DAF 1.01DETE HEIGHT 1 11.0 90.0 DAF 1.01DETE HEIGHT 1 11.0 135.0 DAF 1.01DETE HEIGHT 0 12.0 0.0DETE HEIGHT 0 12.0 45.0DETE HEIGHT 0 12.0 90.0DETE HEIGHT 0 12.0 135.0YEAR 50.0PRIN XCHE DETA USAG SUMM SCFESTOP

4.4.3. Spectral Analysis

This type of analysis requires three compulsory sets of data and two optional sets:

• Target fatigue life (YEAR). Computed lives below this figure will be reported as having failed. This is

compulsory.

• Transfer function definition. It is normal to assign all the analyzed waves for a given direction to a par-

ticular transfer function. This is achieved using the TRANSFER command which also permits dynamic

amplification factors to be applied. This is compulsory.

• Sea state spectra definition. For each transfer function a series of sea state spectra are defined using

the SPECTRUM command. A variety of spectra are available viz:




Scott-Weigel

JONSWAP

Pierson-Moskowitz

Ochi-Hubble

Each spectrum is associated with a probability of occurrence. This command is compulsory.

• Wave spreading effects may be included using the SPREAD command. Three spreading functions are

available including those associated with Mitsuyasu (Ref. 8) and Goda (Ref. 9). This command is optional.

• Additional frequencies may be defined at which the transfer function is to be computed. This permits

a limited number of waves to be structurally analyzed whilst providing a more detailed fatigue definition

and is particularly suitable for structures that respond linearly to increasing wave heights. This command

is optional.

Table 4.1 Spectral Commands


CSelects spectral analysis methodANALYSIS SPEC-

TRAL

CSelects joints at which fatigue lives are calculatedJOINT













4CDefault SCF valueSCF TUB DEFAULT

4CDefault SCF valueSCF RHS DEFAULT

4CDefault SCF valueSCF WF DEFAULT

4CDefault SCF valueSCF BOX DE-

FAULT

Default SCF equations to be used in generationSCF AUTO DE-

FAULT

SCF equations to be used at specific jointsSCF AUTO JOINT

SCF values at specific inspection points on tubular bracesSCFANGLE

User defined SCF values for non-tubular bracesSCFBRACE






SCF values at specific inspection points on non-tubular

braces

SCFPOINT


Gravitational acceleration termACCE

S-N damage curve definitionCURVE

Additional interpolated frequenciesFREQUENCY

5CUser defined S-N curve assignmentS-N

6CStress histogram informationSIGM

CWave spectrum probabilitiesSPECTRUM

Requests wave spreadingSPREADING

CTransfer function dataTRANSFER




Usage

C


Notes








5. S-N data does not have to be supplied if a stress histogram report has been requested using the PRINT

command.

6. Stress histogram information is only required if requested using the PRINT command.


4.4.3.1. Spectral Analysis Example


• Automatic wave information recovery

• Explicit SCF definitions using @ file facility

• Secondary elements

• Design data for leg members

• Utilizes built in S-N curve with thickness correction and user defined power

• Four sea-states




Example 4.2 Example of Spectral Analysis Data File

WAVE AUTO*THE FOLLOWING JOINTS ARE CONNECTED TO AN ELEMENTJOIN 1110 2210 1120 1210 1520 2130 1420 1130 1540 1140 1150 1440 1250 2250: 1310 1350 2330 1330 2520 2540 2110 2120 3130 3210 2420 2140 2150 2440 3250: 2310 2350 3350 3310 3420 3440 3110 3120 4130 3520 4210 3540 3140 3150 4250: 3330 4330 4110 4150 4310 4350*DEFINE DESIGN PROPERTIES FOR LEG MEMBERSDESIGN.PROPERTIES TUB 2.4 0.05 GROUP 8SECO ELEM 1505 1506 1509 504 1510 503 514 513 524 523 1401 825 1201 1203 827: 1402 1204 1501 1202 1502 1503 1504S-N APXD ELEM ALLTHICKNESS.CORRECTION 0.25 *POWER SET TO 0.25 INSTEAD OF DEFAULT 0.3TRAN 100 1 1.0030 2 1.0119 3 1.0215 4 1.0340 5 1.0496 6 1.0689TRAN 100 7 1.0919 8 1.1197 9 1.1850 10 1.2726 11 1.3607 12 1.4718SPEC 100 PMOS 0.25 2.5 0.1121SPEC 100 PMOS 0.25 3.5 1.4573SPEC 100 PMOS 0.25 4.5 2.6904SPEC 100 PMOS 0.25 5.5 1.6815SPEC 100 PMOS 0.25 6.5 0.5605SPEC 100 PMOS 0.25 7.5 0.1121SPEC 100 PMOS 0.75 2.5 0.3363SPEC 100 PMOS 0.75 3.5 8.5196SPEC 100 PMOS 0.75 4.5 11.7705SPEC 100 PMOS 0.75 5.5 7.6228SPEC 100 PMOS 0.75 6.5 3.363SPEC 100 PMOS 0.75 7.5 0.5605SPEC 100 PMOS 1.25 3.5 4.9324SPEC 100 PMOS 1.25 4.5 11.6584SPEC 100 PMOS 1.25 5.5 9.7527SPEC 100 PMOS 1.25 6.5 4.9324SPEC 100 PMOS 1.25 7.5 1.2331SPEC 100 PMOS 1.25 8.5 0.1121SPEC 100 PMOS 1.75 3.5 0.5605SPEC 100 PMOS 1.75 4.5 5.7171SPEC 100 PMOS 1.75 5.5 7.7349SPEC 100 PMOS 1.75 6.5 4.2598SPEC 100 PMOS 1.75 7.5 1.3452SPEC 100 PMOS 1.75 8.5 0.1121SPEC 100 PMOS 2.25 4.5 1.7936SPEC 100 PMOS 2.25 5.5 4.8203SPEC 100 PMOS 2.25 6.5 3.2509SPEC 100 PMOS 2.25 7.5 1.0089SPEC 100 PMOS 2.25 8.5 0.1121SPEC 100 PMOS 2.75 4.5 0.2242SPEC 100 PMOS 2.75 5.5 1.9057SPEC 100 PMOS 2.75 6.5 2.242SPEC 100 PMOS 2.75 7.5 0.7847SPEC 100 PMOS 2.75 8.5 0.1121SPEC 100 PMOS 3.25 5.5 0.5605SPEC 100 PMOS 3.25 6.5 1.2331SPEC 100 PMOS 3.25 7.5 0.5605SPEC 100 PMOS 3.25 8.5 0.1121SPEC 100 PMOS 3.75 5.5 0.1121SPEC 100 PMOS 3.75 6.5 0.4484SPEC 100 PMOS 3.75 7.5 0.3363SPEC 100 PMOS 3.75 8.5 0.1121SPEC 100 PMOS 4.25 6.5 0.1121SPEC 100 PMOS 4.25 7.5 0.2242SPEC 100 PMOS 4.25 8.5 0.1121SPEC 100 PMOS 4.75 7.5 0.1121SPEC 100 PMOS 4.75 8.5 0.1121SPEC 100 PMOS 5.25 8.5 0.1121TRAN 200 13 1.0030 14 1.0119 15 1.0215 16 1.0340 17 1.0496 18 1.0689TRAN 200 19 1.0919 20 1.1197 21 1.1850 22 1.2726 23 1.3607 24 1.4718SPEC 200 PMOS 0.25 2.5 0.1413SPEC 200 PMOS 0.25 3.5 1.8369SPEC 200 PMOS 0.25 4.5 3.3912SPEC 200 PMOS 0.25 5.5 2.1195SPEC 200 PMOS 0.25 6.5 0.7065SPEC 200 PMOS 0.25 7.5 0.1413



SPEC 200 PMOS 0.75 2.5 0.4239SPEC 200 PMOS 0.75 3.5 10.7388SPEC 200 PMOS 0.75 4.5 14.8365SPEC 200 PMOS 0.75 5.5 9.6084SPEC 200 PMOS 0.75 6.5 4.239SPEC 200 PMOS 0.75 7.5 0.7065SPEC 200 PMOS 1.25 3.5 6.2172SPEC 200 PMOS 1.25 4.5 14.6952SPEC 200 PMOS 1.25 5.5 12.2931SPEC 200 PMOS 1.25 6.5 6.2172SPEC 200 PMOS 1.25 7.5 1.5543SPEC 200 PMOS 1.25 8.5 0.1413SPEC 200 PMOS 1.75 3.5 0.7065SPEC 200 PMOS 1.75 4.5 7.2063SPEC 200 PMOS 1.75 5.5 9.7497SPEC 200 PMOS 1.75 6.5 5.3694SPEC 200 PMOS 1.75 7.5 1.6956SPEC 200 PMOS 1.75 8.5 0.1413SPEC 200 PMOS 2.25 4.5 2.2608SPEC 200 PMOS 2.25 5.5 6.0759SPEC 200 PMOS 2.25 6.5 4.0977SPEC 200 PMOS 2.25 7.5 1.2717SPEC 200 PMOS 2.25 8.5 0.1413SPEC 200 PMOS 2.75 4.5 0.2826SPEC 200 PMOS 2.75 5.5 2.4021SPEC 200 PMOS 2.75 6.5 2.826SPEC 200 PMOS 2.75 7.5 0.9891SPEC 200 PMOS 2.75 8.5 0.1413SPEC 200 PMOS 3.25 5.5 0.7065SPEC 200 PMOS 3.25 6.5 1.5543SPEC 200 PMOS 3.25 7.5 0.7065SPEC 200 PMOS 3.25 8.5 0.1413SPEC 200 PMOS 3.75 5.5 0.1413SPEC 200 PMOS 3.75 6.5 0.5652SPEC 200 PMOS 3.75 7.5 0.4239SPEC 200 PMOS 3.75 8.5 0.1413SPEC 200 PMOS 4.25 6.5 0.1413SPEC 200 PMOS 4.25 7.5 0.2826SPEC 200 PMOS 4.25 8.5 0.1413SPEC 200 PMOS 4.75 7.5 0.1413SPEC 200 PMOS 4.75 8.5 0.1413SPEC 200 PMOS 5.25 8.5 0.1413TRAN 300 25 1.0030 26 1.0119 27 1.0215 28 1.0340 29 1.0496 30 1.0689TRAN 300 31 1.0919 32 1.1197 33 1.1850 34 1.2726 35 1.3607 36 1.4718SPEC 300 PMOS 0.25 2.5 0.1973SPEC 300 PMOS 0.25 3.5 2.5649SPEC 300 PMOS 0.25 4.5 4.7352SPEC 300 PMOS 0.25 5.5 2.9595SPEC 300 PMOS 0.25 6.5 0.9865SPEC 300 PMOS 0.25 7.5 0.1973SPEC 300 PMOS 0.75 2.5 0.5919SPEC 300 PMOS 0.75 3.5 14.9948SPEC 300 PMOS 0.75 4.5 20.7165SPEC 300 PMOS 0.75 5.5 13.4164SPEC 300 PMOS 0.75 6.5 5.919SPEC 300 PMOS 0.75 7.5 0.9865SPEC 300 PMOS 1.25 3.5 8.6812SPEC 300 PMOS 1.25 4.5 20.5192SPEC 300 PMOS 1.25 5.5 17.1651SPEC 300 PMOS 1.25 6.5 8.6812SPEC 300 PMOS 1.25 7.5 2.1703SPEC 300 PMOS 1.25 8.5 0.1973SPEC 300 PMOS 1.75 3.5 0.9865SPEC 300 PMOS 1.75 4.5 10.0623SPEC 300 PMOS 1.75 5.5 13.6137SPEC 300 PMOS 1.75 6.5 7.4974SPEC 300 PMOS 1.75 7.5 2.3676SPEC 300 PMOS 1.75 8.5 0.1973SPEC 300 PMOS 2.25 4.5 3.1568SPEC 300 PMOS 2.25 5.5 8.4839SPEC 300 PMOS 2.25 6.5 5.7217SPEC 300 PMOS 2.25 7.5 1.7757




SPEC 300 PMOS 2.25 8.5 0.1973SPEC 300 PMOS 2.75 4.5 0.3946SPEC 300 PMOS 2.75 5.5 3.3541SPEC 300 PMOS 2.75 6.5 3.946SPEC 300 PMOS 2.75 7.5 1.3811SPEC 300 PMOS 2.75 8.5 0.1973SPEC 300 PMOS 3.25 5.5 0.9865SPEC 300 PMOS 3.25 6.5 2.1703SPEC 300 PMOS 3.25 7.5 0.9865SPEC 300 PMOS 3.25 8.5 0.1973SPEC 300 PMOS 3.75 5.5 0.1973SPEC 300 PMOS 3.75 6.5 0.7892SPEC 300 PMOS 3.75 7.5 0.5919SPEC 300 PMOS 3.75 8.5 0.1973SPEC 300 PMOS 4.25 6.5 0.1973SPEC 300 PMOS 4.25 7.5 0.3946SPEC 300 PMOS 4.25 8.5 0.1973SPEC 300 PMOS 4.75 7.5 0.1973SPEC 300 PMOS 4.75 8.5 0.1973SPEC 300 PMOS 5.25 8.5 0.1973TRAN 400 37 1.0030 38 1.0119 39 1.0215 40 1.0340 41 1.0496 42 1.0689TRAN 400 43 1.0919 44 1.1197 45 1.1850 46 1.2726 47 1.3607 48 1.4718SPEC 400 PMOS 0.25 2.5 0.1189SPEC 400 PMOS 0.25 3.5 1.5457SPEC 400 PMOS 0.25 4.5 2.8536SPEC 400 PMOS 0.25 5.5 1.7835SPEC 400 PMOS 0.25 6.5 0.5945SPEC 400 PMOS 0.25 7.5 0.1189SPEC 400 PMOS 0.75 2.5 0.3567SPEC 400 PMOS 0.75 3.5 9.0364SPEC 400 PMOS 0.75 4.5 12.4845SPEC 400 PMOS 0.75 5.5 8.0852SPEC 400 PMOS 0.75 6.5 3.567SPEC 400 PMOS 0.75 7.5 0.5945SPEC 400 PMOS 1.25 3.5 5.2316SPEC 400 PMOS 1.25 4.5 12.3656SPEC 400 PMOS 1.25 5.5 10.3443SPEC 400 PMOS 1.25 6.5 5.2316SPEC 400 PMOS 1.25 7.5 1.3079SPEC 400 PMOS 1.25 8.5 0.1189SPEC 400 PMOS 1.75 3.5 0.5945SPEC 400 PMOS 1.75 4.5 6.0639SPEC 400 PMOS 1.75 5.5 8.2041SPEC 400 PMOS 1.75 6.5 4.5182SPEC 400 PMOS 1.75 7.5 1.4268SPEC 400 PMOS 1.75 8.5 0.1189SPEC 400 PMOS 2.25 4.5 1.9024SPEC 400 PMOS 2.25 5.5 5.1127SPEC 400 PMOS 2.25 6.5 3.4481SPEC 400 PMOS 2.25 7.5 1.0701SPEC 400 PMOS 2.25 8.5 0.1189SPEC 400 PMOS 2.75 4.5 0.2378SPEC 400 PMOS 2.75 5.5 2.0213SPEC 400 PMOS 2.75 6.5 2.378SPEC 400 PMOS 2.75 7.5 0.8323SPEC 400 PMOS 2.75 8.5 0.1189SPEC 400 PMOS 3.25 5.5 0.5945SPEC 400 PMOS 3.25 6.5 1.3079SPEC 400 PMOS 3.25 7.5 0.5945SPEC 400 PMOS 3.25 8.5 0.1189SPEC 400 PMOS 3.75 5.5 0.1189SPEC 400 PMOS 3.75 6.5 0.4756SPEC 400 PMOS 3.75 7.5 0.3567SPEC 400 PMOS 3.75 8.5 0.1189SPEC 400 PMOS 4.25 6.5 0.1189SPEC 400 PMOS 4.25 7.5 0.2378SPEC 400 PMOS 4.25 8.5 0.1189SPEC 400 PMOS 4.75 7.5 0.1189SPEC 400 PMOS 4.75 8.5 0.1189SPEC 400 PMOS 5.25 8.5 0.1189YEAR 50.0



PRIN XCHE DETA USAG SUMM SCFESTOP

4.4.4. Stress History Analysis

This type of analysis requires two sets of data:


• Wave occurrence data in the form of number of occurrences per year (DETM). This data may either ex-

plicitly reference waves that have been analyzed; that is, referred to in the WAVE data, or may consist

of wave height occurrences, in which case interpolation is carried out to obtain member forces for wave

heights that have not been analyzed. This second approach permits a limited number of waves to be

structurally analyzed whilst providing a much more detailed fatigue definition.

Table 4.2 Stress History Commands


CSelects stress history analysis methodANALYSIS

STRESS HIS-

TORY















FAULT

4CDefault SCF valueSCF RHS DE-

FAULT

4CDefault SCF valueSCF WF DE-

FAULT


FAULT

Default SCF equations to be used in generationSCF AUTO DE-

FAULT


JOINT










braces

SCFPOINT


Allowable stressALLOWABLE

5CUser defined S-N damage curve definitionCURVE


6CS-N curve assignmentS-N




Usage

C


Notes








5. S-N data does not have to be supplied if a stress histogram report has been requested using the PRINT

command.

6. Stress histogram information is only required if requested using the PRINT command.


4.4.4.1. Stress History Analysis Example


• Explicit wave information defined

• Automatic generation of influence functions

• Secondary elements

• Utilizes built in S-N curve with thickness correction

• Analyses wave occurrence definition



Example 4.3 Example of Stress History Analysis Data File

SYSTEM DATA AREA 200000PROJECT FATIJOB POSTFILES JACFTITLE FATJACK USER MANUAL EXAMPLEOPTIONS NODL NOBL PRNO DATA GOON INFLUNITS KN MENDANALYSIS STRESS HISTORYSCF TUBE DEFAULT 1.0 1.0 1.0 1.0 1.0 1.0SCF AUTOMATIC DEFAULT GENERAL EFTHYMIOUSCF AUTOMATIC JOINT: 1110 2210 1120 1210 1520 2130 1420 1130 1540 1140 1150 1440: 1310 1350 2330 1330 2520 2540 2110 2120 3130 3210 2420 2140 2150 2440 3250: 2310 2350 3350 3310 3420 3440 3110 3120 4130 3520 4210 3540 3140 3150 4250: 3330 4330 4110 4150 4310 4350 2250 1250WAVE 1 1.0 5.0 0.0 NPOS 6WAVE 2 2.0 6.2 0.0 NPOS 6WAVE 3 3.0 7.1 0.0 NPOS 6WAVE 4 4.0 7.7 0.0 NPOS 6WAVE 5 5.0 8.2 0.0 NPOS 6WAVE 6 6.0 8.7 0.0 NPOS 6WAVE 7 7.0 9.1 0.0 NPOS 6WAVE 8 8.0 9.5 0.0 NPOS 6WAVE 9 9.0 9.8 0.0 NPOS 6WAVE 10 10.0 10.2 0.0 NPOS 6WAVE 11 11.0 10.6 0.0 NPOS 6WAVE 12 12.0 11.0 0.0 NPOS 6WAVE 13 1.0 5.0 90.0 NPOS 6WAVE 14 2.0 6.2 90.0 NPOS 6WAVE 15 3.0 7.1 90.0 NPOS 6WAVE 16 4.0 7.7 90.0 NPOS 6WAVE 17 5.0 8.2 90.0 NPOS 6WAVE 18 6.0 8.7 90.0 NPOS 6WAVE 19 7.0 9.1 90.0 NPOS 6WAVE 20 8.0 9.5 90.0 NPOS 6WAVE 21 9.0 9.8 90.0 NPOS 6WAVE 22 10.0 10.2 90.0 NPOS 6WAVE 23 11.0 10.6 90.0 NPOS 6WAVE 24 12.0 11.0 90.0 NPOS 6WAVE 25 1.0 5.0 45.0 NPOS 6WAVE 26 2.0 6.2 45.0 NPOS 6WAVE 27 3.0 7.1 45.0 NPOS 6WAVE 28 4.0 7.7 45.0 NPOS 6WAVE 29 5.0 8.2 45.0 NPOS 6WAVE 30 6.0 8.7 45.0 NPOS 6WAVE 31 7.0 9.1 45.0 NPOS 6WAVE 32 8.0 9.5 45.0 NPOS 6WAVE 33 9.0 9.8 45.0 NPOS 6WAVE 34 10.0 10.2 45.0 NPOS 6WAVE 35 11.0 10.6 45.0 NPOS 6WAVE 36 12.0 11.0 45.0 NPOS 6WAVE 37 1.0 5.0 135.0 NPOS 6WAVE 38 2.0 6.2 135.0 NPOS 6WAVE 39 3.0 7.1 135.0 NPOS 6WAVE 40 4.0 7.7 135.0 NPOS 6WAVE 41 5.0 8.2 135.0 NPOS 6WAVE 42 6.0 8.7 135.0 NPOS 6WAVE 43 7.0 9.1 135.0 NPOS 6WAVE 44 8.0 9.5 135.0 NPOS 6WAVE 45 9.0 9.8 135.0 NPOS 6WAVE 46 10.0 10.2 135.0 NPOS 6WAVE 47 11.0 10.6 135.0 NPOS 6WAVE 48 12.0 11.0 135.0 NPOS 6*THE FOLLOWING JOINTS ARE CONNECTED TO AN ELEMENTJOINT 1110 2210 1120 1210 1520 2130 1420 1130 1540 1140 1150 1440 1250 2250: 1310 1350 2330 1330 2520 2540 2110 2120 3130 3210 2420 2140 2150 2440 3250: 2310 2350 3350 3310 3420 3440 3110 3120 4130 3520 4210 3540 3140 3150 4250: 3330 4330 4110 4150 4310 4350SECONDARY ELEMENTS 1505 1506 1509 504 1510 503 514




: 513 524 523 1401 825 1201 1203 827: 1402 1204 1501 1202 1502 1503 1504S-N DET ELEM ALLTHICKNESS.CORRECTIONDETERMINISTIC.DATA 1 699458DETERMINISTIC.DATA 2 180369DETERMINISTIC.DATA 3 46512DETERMINISTIC.DATA 4 11994DETERMINISTIC.DATA 5 3093DETERMINISTIC.DATA 6 798DETERMINISTIC.DATA 7 206DETERMINISTIC.DATA 8 53DETERMINISTIC.DATA 9 14DETERMINISTIC.DATA 10 4DETERMINISTIC.DATA 11 1DETERMINISTIC.DATA 12 0DETERMINISTIC.DATA 13 615024DETERMINISTIC.DATA 14 167650DETERMINISTIC.DATA 15 45700DETERMINISTIC.DATA 16 12457DETERMINISTIC.DATA 17 3396DETERMINISTIC.DATA 18 926DETERMINISTIC.DATA 19 252DETERMINISTIC.DATA 20 69DETERMINISTIC.DATA 21 19DETERMINISTIC.DATA 22 5DETERMINISTIC.DATA 23 1DETERMINISTIC.DATA 24 0DETERMINISTIC.DATA 25 685279DETERMINISTIC.DATA 26 167805DETERMINISTIC.DATA 27 41091DETERMINISTIC.DATA 28 10062DETERMINISTIC.DATA 29 2464DETERMINISTIC.DATA 30 603DETERMINISTIC.DATA 31 148DETERMINISTIC.DATA 32 36DETERMINISTIC.DATA 33 9DETERMINISTIC.DATA 34 2DETERMINISTIC.DATA 35 1DETERMINISTIC.DATA 36 0DETERMINISTIC.DATA 37 568370DETERMINISTIC.DATA 38 156061DETERMINISTIC.DATA 39 42851DETERMINISTIC.DATA 40 11766DETERMINISTIC.DATA 41 3231DETERMINISTIC.DATA 42 887DETERMINISTIC.DATA 43 244DETERMINISTIC.DATA 44 67DETERMINISTIC.DATA 45 18DETERMINISTIC.DATA 46 5DETERMINISTIC.DATA 47 1DETERMINISTIC.DATA 48 0YEAR 50.0PRIN XCHE DETA USAG SUMM SCFESTOP

4.4.5. Time History Analysis

This type of analysis requires three sets of data:


• Occurrence data of the time histories defined in the HIST data in the form of occurrences per year

(DETE).



• Rainflow counting data (CYCLE)

Table 4.3 Time History Commands


CSelects time history analysis methodANALYSIS

TIME HIS-

TORY


CSpecifies time history information from analysisHIST




Default gap dimensionGAPDE-

FAULT









FAULT

3CDefault SCF valueSCF RHS DE-

FAULT

3CDefault SCF valueSCF WF DE-

FAULT


FAULT

Default SCF equations to be used in generationSCF AUTO

DEFAULT


JOINT




Minimum SCF valuesSCFMINIM-

UM


braces

SCFPOINT


User defined S-N damage curve definitionCURVE

CRainflow counting dataCYCLE






CS-N curve assignmentS-N




Usage

C


Notes







4.4.5.1. Time History Analysis Example


• New structure defined

• Time history results retrieved from multiple structures

• Time history occurrence specified with probabilities

• Stress range intervals for cycle counting computed automatically

Example 4.4 Example of Time History Analysis Data File

JOB POSTPROJECT T206STRUCTURE A206NEWSTRUCTURE N206TITLE FATJACK USER MANUAL EXAMPLEOPTIONS GOON ENDUNITS KN MENDANALYSIS TIME HISTORYHIST 1 A206 80 880HIST 2 B206 80 880HIST 3 C206 80 880HIST 11 D206 80 880HIST 12 E206 80 880HIST 13 F206 80 880HIST 21 G206 80 880HIST 22 H206 80 880HIST 23 I206 80 880JOIN 2 5 7INSP 8 ELEM ALLSCF TUBE DEFA 3.0SCF AUTO DEFA K K K K W K K K WSCF AUTO DEFA KT K K K W K K K WSCF AUTO JOIN 2 5 7



CURV USER SINGLE 35.0E3 1.0E7 3.0S-N USER ELEM ALLGAPD WORD 0.05GAPD KUAN 0.05YEAR 30.0DETE 21 PROB 200DETE 22 PROB 100.0DETE 23 PROB 100DETE 11 PROB 200DETE 12 PROB 60.0DETE 13 PROB 40.0DETE 1 PROB 50DETE 2 PROB 30.0DETE 3 PROB 20.0CYCLE 20PRINT FULL DETAILED SCFP SCFE USAGE XCHESTOP

4.5. ACCE

The ACCE command defines the value for gravitational acceleration required for spectral fatigue analysis.

Parameters

ACCE

Keyword

gravity

Gravitational acceleration (Real).

Notes

1. This command is optional for a SPECTRAL analysis. If not defined the program will adopt a value of

9.81 metres/sec2 (converted into the appropriate analysis units). If required the default value may be

overwritten using the ACCE command.

2. If used, the command should be defined only once.

Examples

ACCE 32.2

4.6. ALLOWABLE

The ALLOWABLE command is used to request that the computed stress value from a Stress History

Analysis is compared with a target (limit) value when PRINT PEAK or PRINT RNGE is also requested. If

the command is used FATJACK will report a utilization factor rather than a direct stress.

Parameters

ALLOWABLE: Keyword.



ALLOWABLE

value: Allowable stress to the actual stress (PEAK or RNGE) is compared. (Real).

Notes

1. This command is optional for a STRESS HISTORY analysis.

4.7. ANSYS

The ANSYS command defines the name of the Mechanical APDL job(s) from which the analysis results

will be obtained.

The ANSYS command is a preliminary command, and should only appear at the head of the

FATJACK data set.

Parameters

ANSYS

Keyword

FNAME

Keyword to denote that the job names are specified in a job name list file (Optional).

Jobname

• without FNAME – job name of the Mechanical APDL model to be processed. This is the name asso-

ciated with the .RST file generated by Mechanical APDL (Alphanumeric, up to 32 characters).

• with FNAME – name of file containing paths and names of Mechanical APDL jobs to be included in

the analysis together.

youngs

Young's Modulus (Optional, Real).

density

Material density (Optional, Real).

Usage

The command is mandatory if FATJACK is to be performed following a Mechanical APDL analysis and

must be omitted otherwise.

Notes

1. FATJACK will only process certain Mechanical APDL beam element types in a Mechanical APDL model.

Valid element names are:

BEAM44, BEAM188, BEAM189, PIPE16, PIPE59, PIPE288, PIPE289

Examples

1. The Mechanical APDL analysis is a single job called ANSYSJOB. All the load cases in this job will be

analyzed in FATJACK.

ANSYS ANSYSJOB



2. The Mechanical APDL analysis information is contained in a job name file called Ansysfile.txt,

which references three Mechanical APDL jobs called Ansysjob1, Ansysjob2 and Ansysjob3 located in

different directories.

ANSYS FNAME Ansysfile.txt

The contents of file Ansysfile.txt are:

C:\AnsysAnalysis\Job1\Ansysjob1



4.8. CHORD

The CHORD command allows specific elements to be defined as chord members at a particular joint.

Optional chord lengths and end fixity may also be defined if required.

Parameters

CHORD

Keyword

joint

Joint number at which the chord is being defined (Integer).

member

User element number defining a segment of the chord associated with the specified joint. If computed

chord lengths are required then all the members defining the chord must be supplied (Integer).

LENGTH

Keyword to indicate that the chord length is to follow.

length

Length of the chord to be used in SCF computations. (Real).

FIXITY

Keyword to indicate that the chord end fixity parameter is to follow.

para

Chord end fixity parameter used in the computation of SCF values using Efthymiou equations. (Real).

Usage

This command is compulsory if joints modelled with two or three nodes points are required.

Notes

1. For joints modelled with a single node, this command is optional and the criteria for selecting chord

elements are described below. In cases where the chord member is segmented, however, it is suggested

that a chord command is supplied in order that the correct chord length is utilized in any automated

SCF computations.



CHORD

i. Select all tubes at the current node with largest diameter.

ii. From those selected in (i), select all tubes with largest thickness.

iii. If the list selected in (ii), contains only one element then this becomes the chord.

iv. If the list selected in (ii), contains more than one element then the list is checked for a pair of co-

linear elements forming a through member. If only one pair is found then these elements for the

chord.

v. If no unique chord element(s) can be found then automatic SCF calculation is not possible. In

these circumstances, the chord element(s) must be defined manually.

vi. The chord length is computed as 2/3 of the combined lengths of the chosen chords. The chord

end fixity parameter is set to 0.7.

2. If K or KT joints are to be modelled with more than one node, a chord command must be supplied to

provide the connectivity information between the nodes at the joint. For KT joints modelled with three

nodes, the joint number must be the central node and the chord elements must connect the three

braces together (See the TYPE command).

3. If not defined, the chord length is computed as 2/3 of the combined lengths of the selected chord

elements.

4. If not defined, the chord end fixity parameter is set to 0.7.

A value of 0.5 represents fixed end conditions.

A value of 1.0 represents pin end conditions.

Examples

CHOR 2000 2010 2020 2030 2040CHOR 10 110 120 LENG 20.0CHOR 105 1150 1250 FIX 0.8CHOR 20 120 LENG 18.5 FIX 0.7

4.9. COMPONENT

The COMPONENT command is used to define the component to be processed from a substructure

analysis.

The COMP command is a preliminary command, and should only appear at the head of the FATJACK

data set.

Parameters

COMPONENT

Keyword

sname

Structure name identifying which existing structure is to be accessed from the current project, see the

PROJ command (Alphanumeric, 4 characters, the first character must be alphabetic).

tree

This is the path down the component tree from the given structure in sname to the component which

is being used for the FATJACK processing.



Usage

Valid only, and compulsory, for recovered components.

Notes

1. If the user is processing the global structure run in a substructure analysis, use only the STRU command.

Examples

To process the second level component CMP2, part of assembled component CMP1, which in turn is

part of structure STRU:

COMP STRU CMP1 CMP2

4.10. CURVE

The CURVE command defines the relationship between stress range and number of cycles to failure

used in computing the damage contribution of the applied wave loading.

Standard curves available within FATJACK do not need to be defined unless non-standard base

thicknesses are required for thickness correction.

4.10.1. CURVE Command (User defined S-N curves)

Parameters

CURVE

Keyword

name

Alphanumeric identifier to be associated with this curve (up to 4 characters).

SINGLE

Alphanumeric identifier to be associated with this curve (up to 4 characters).

MULTI

Keyword to denote a multi-linear curve is being defined.

LIMIT

Keyword to denote a single slope curve with a cut-off stress is being defined.

stress, cycle

Point lying on a given section of the S-N curve. For multi-linear curves the point must correspond to the

intersect within the adjacent section. For limiting curves the point must correspond to the cut-off position

(Real).

slope

Slope of a given section of the S-N curve (Real).

THICK

Keyword to indicate that a base thickness is to be provided.



CURVE

base

Base thickness to be used if thickness correction requested (Real).

Notes

1. The built in design curves equate to the following S-N definitions.

Base ThicknessSlopeCycleStress

(N/mm2)

TYPECurve

32mm3.05.01.0D71.0D752.6340452.63404MULTIDET

22mm3.05.01.0D71.0D735.0536635.05366MULTIDEF2

25mm4.382.0D834.94451LIMITAPX

16mm3.742.0D823.06045LIMITAPXD

N/A (must be user defined)4.12.0D833.81812MULTIDET

Although the above curves are given in N and mm, any user entries are in data input units.

2. The requirement for the ordinates of user defined multi-linear S-N curves to be at the intersection of

adjacent sections is that two pairs of ordinates will be the same, but with differing slopes. This can be

seen in the internal representations above of DET and DEF2 design curves (which are both bi-linear).

3. The base thickness is used when thickness correction of the S-N curve is requested (using the THICK-

NESS command). For user defined curves a base thickness must be provided if the correction is to be

applied.

Examples

CURV DOC LIMIT 32.0 2.0D8 3.56CURV DSC MULTI 73.0 1.0D7 3.56: 73.0 1.0D7 4.56

4.10.2. CURVE Command (Base thickness definition for standard curves)

Parameters

CURVE

Keyword

curve

Predefined S-N curve name. Only required when base thickness is to be modified from the default value.

The following curves are currently available:

Department of Energy T and F2 curvesDET, DEF2

API RP2A X and X’ curvesAPX, APXD

Danish Offshore Regulations DS412 tubular curveDOT

THICK

Keyword to indicate that a base thickness is to be provided.



base

Base thickness to be used if thickness correction requested (Real).

Note

1. The base thickness is used when thickness correction of the S-N curve is requested (using the THICK-

NESS command). For the predefined curves (with the exception of the DOT curve) a default base

thickness is adopted unless otherwise overridden by the user. For the DOT curve, no default base

thickness is available and a user defined value must be provided if thickness correction is required.

Example

CURV DET THICK 30.0

4.11. CYCLE

The CYCLE command defines the number and sizes of the stress range intervals for rainflow counting.

Parameters

CYCLE

Keyword

nint

Number of intervals to sample stress range (Integer, >0).

sigmax

Peak stress range required. If zero or not specified, the peak is determined automatically from the stress

time history (Real, >=0.0).

sig1

Stress range limit for the first interval (Real, >=0.0).

Usage

Mandatory for time history analysis.

Notes

1. If sigmax and sig1 are both specified, sigmax must be larger than sig1.

2. If sig1 is not specified, the nint intervals will be set equally between zero and sigmax or the program

determined peak value if this is not defined.

3. If sig1 is specified, the first stress range interval will be taken as between zero and sig1. The rest

(nint-1) intervals will be set equally between sig1 and sigmax or the program determined peak value

if this is not defined.

Examples

CYCLE 50CYCLE 50 10.0E6 1.0E6

If you had a number of stress ranges counted, say: 1.1, 1.9, 3.1, 4.4, 9



CYCLE

If you use CYCLE 3 10.5, then you would get counting results with the following:

: 30 – 3.5

: 13.5 - 7.0

: 17.0 - 10.5

If you use CYCLE 3 then you would get counting results with the following:

: 20 – 3

: 23 - 6

: 16 - 9

If you use CYCLE 3 10 2, then you would get counting results with the following:

: 20 – 2

: 22 - 6

: 16 - 10

4.12. DESIGN

The DESI command enables geometric properties from the structural analysis to be overridden to account

for design requirements. The design properties are used for computing member stresses and SCF values.

In the absence of any design data the geometric information from the analysis will be adopted.

Parameters

DESIGN

Keyword

type

Section type (Alphanumeric). Valid profiles are:

TUB

Tube

WF

Doubly symmetric Rolled I-section (for example, UB, UC, Joist,WFC, WF)

RHS

Rectangular Hollow Section (RHS)

BOX

Fabricated Box Section

values

Values defining the section dimensions appropriate to the section type. See Section Profile Informa-

tion (p. 115) for details (Real).



STEP

Keyword to indicate the step number is to follow.

istep

Step number for non-prismatic elements. Values should either be 1 or the last step number for the ele-

ment. Alternatively the keywords END1 or END2 may replace STEP istep.

ELEMENT

Keyword to denote selection by element numbers.

GROUP

Keyword to denote selection by element group numbers.

PROPERTY

Keyword to denote selection by geometric property integer.

list

List of user element, group or geometric property numbers for which this data is to be assigned. The

list may include the keyword TO but not ALL.

Notes

1. Non-tubular sections must not be applied to TUBE elements.

2. If a step reference is given only that step for the elements specified within the element, group or

property list will be assigned the new section data.

3. See FATJACK Priority of Data Assignments (p. 47) for order of priority for ELEMENT/GROUP/PROPERTY

lists.

4. If insets are defined for the end of a brace, any design properties defined for the same end will be

applied at the inset position.

Examples

DESI TUB 2.0 0.04 ELEM 100 TO 110DESI TUB 1.5 0.032 END1 ELEM 1010DESI BOX 2.0 1.5 0.04 0.032

4.13. DETE

The DETE command defines the wave occurrence data required for deterministic and stress history

analyses. Facilities exist to include additional wave definitions that were not included in the wave ana-

lysis. This command is also required in time history analysis to define the occurrence of each time history

case.

Parameters

DETE

Keyword

case

Wave case number to which this occurrence data relates (Integer).



DETE

ncycle

Number of cycles per year for this wave case (Integer).

HEIGHT

Keyword to denote that the occurrence data is to be given in terms of a reference height for a given

direction.

height

Reference wave height (Real).

direction

Reference wave direction (Real, degrees).

DAF

Keyword to denote that the occurrence data is to be given as probability.

daf

Dynamic amplification factor.

PROB

Keyword to denote that the occurrence data is to be given as probability.

pval

Occurrence probability of the wave history case (Real, >+0.0).

Notes

1. For wave cases generated using the WAVE AUTO command, these are numbered sequentially from

1.

2. If the dynamic amplification factor keyword and value are not supplied, unity is assumed. The dynamic

amplification factor data is always ignored in the time history analyses.

3. The use of occurrence data relating to reference wave height provides a flexible means to develop

the occurrence data without use of wave case numbers and permitting additional wave height data

to be defined that were not previously analyzed.

For a given wave direction each height defined on a DETE command is related to the associated

analyzed wave cases for the same wave direction.

Stress values for the reference wave height are obtained by linear interpolation between adjacent

wave heights. Stresses for reference wave heights which are below the lower limit of the analyzed

wave cases will be obtained by factoring the limit value.

Stresses for reference wave heights which are above the upper limit of the analyzed wave cases

will be obtained by linear extrapolation of the last two cases. This is shown diagrammatically below.



Using this facility, all wave occurrence data may be defined by reference to the wave height, thus

obviating the need to refer to an analyzed wave case number.

4. The reference height option is not applicable to time history analyses.

5. Keyword PROB is only allowed in time history analyses. However if it is specified, then it must be used

for all DETE commands. The units in which the probability is input are immaterial providing that they

are consistent throughout. The program computes a true probability for each history by dividing each

input probability by the sum of all the probabilities.

Examples

DETE 1 150000DETE 2 124500 DAF 1.05

DETE HEIG 150000 3.5 0.0DETE HEIG 124500 6.0 0.0 DAF 1.10

DETE 1 PROB 1000.0DETE 2 PROB 500.0

4.14. END

The END command is used to terminate a command data block.

The END command is a preliminary command, and should only appear at the head of the FATJACK

data set.

Parameters

END

Keyword

Usage

Compulsory to terminate all command data blocks.

4.15. FILES

The FILES command is used to define the prefix name for the backing files created in this run.

The FILES command is a preliminary command, and should only appear at the head of the FATJACK

data set.

Parameters

FILES

Keyword



FILES

fname

Prefix name for any backing files created by this run. (Alphanumeric, 4 characters, first character must

be alphabetic).

Usage

Optional, if omitted file name defaults to project name.

Notes

1. fname is used as a prefix for all files created during the current run. The four characters are appended

with two digits in the range 12 to 35 to create each individual file.

Examples

FILES BILL

4.16. FREQUENCY

The FREQUENCY command permits the definition of additional frequencies at which the stress transfer

function is to be evaluated in spectral analyses.

Parameters

FREQUENCY

Keyword

trans

Transfer function number to which these additional frequencies are to be added (Integer).

freq-list

List of frequency values. (Real, Hertz).

Notes

1. The frequencies defined MUST lie between the maximum and minimum frequencies associated with

the analyzed wave load cases forming the transfer function.

2. Stresses associated with the additional frequencies will be obtained by linear interpolation of stresses

obtained from adjacent (by frequency) factored analyzed wave loadcases which form the transfer

function.

3. The frequency values must be given in Hertz, this cannot be changed by the use of UNITS command(s).

Examples

FREQ 10 0.142 0.150 0.175: 0.210 0.225

4.17. GAP

The GAP command allows specific gap information to be defined between pairs of braces forming K

and KT joints. For overlapping joints the through member is also defined.



Parameters

GAP

Keyword

joint

Joint number at which the gap is being defined (Integer).

brace

User element number specifying a brace forming part of a K or KT configuration about which the gap

is to be defined (Integer).

brace2

Second user element number corresponding to the second brace (Integer).

gap

User defined gap between braces brace and brace2. For overlapping gaps this dimension should be

negative (Real).

THRU

Keyword to indicate that through brace information is to follow for overlapping braces. Only permissible

if gap is negative.

braced

Brace element number representing the through member. Must be either brace or brace2 defined in

this command (Integer).

Notes

1. If GAP is not specified for a given K or KT joint, the gap adopts the value specified in the GAPDEFAULT

command. If the default gap dimension has not been defined the gap is computed based upon

model geometry. Where gap dimensions are computed these may be reset during the SCF computations

to prevent the use of gap values which would cause the SCF formulations becoming insoluble.

2. The Efthymiou SCF equations permit overlapping K and KT joints. This may be specified by defining a

negative gap value representing the length of the overlap. Under these circumstances, a through brace

must be defined since the equations differ for the through and overlapping member.

Examples

GAP 1100 1100 1110 50.0GAP 1200 1200 1210 -35.0 THRU 1200

4.18. GAPDEFAULT

The GAPDEFAULT command is used to specify a default gap dimension to be used between pairs of

braces forming K and KT joints where specific gaps have not been defined.



GAPDEFAULT

Parameters

GAPDEFAULT

Keyword

equation

Equation type to which this default gap applies. Valid options are:

W

Wordsworth

K

Kuang

D

DS449

E

Efthymiou

gap

Default gap dimension (Real).

Notes

1. If GAPDEFAULT is not specified and a specific gap value is not defined for a given pair of braces

forming a K or KT joint, the gap dimension is computed based upon model geometry. Since joint

geometry is often simplified computed gaps may lead to erroneous values of generated stress concen-

tration factors.

2. If gap dimensions are computed these may be reset during the SCF computations to prevent the use

of gap values which would cause the SCF formulations becoming insoluble.

Examples

GAPDEFAULT WORDSWORTH 50.0

4.19. HIST

The HIST command defines details of the analysis time histories to be included in a time history fatigue

analysis.

Parameters

HIST

Keyword

case

Wave history case number (Integer, > 0).

stru

• For ASAS – name of structure from which data is going to be obtained, structure must be in the

same project as that specified in preliminary data. If omitted, defaults to structure name given in

the preliminary STRUCTURE command (Alphanumeric, 4 characters), or



• For ANSYS – job identification name for the ANSYS job. If omitted, defaults to be first job referenced

(Alphanumeric, up to 8 characters).

start

First system loadcase (load step) to use from this analysis for rainflow counting. If omitted or 0, defaults

to 1 (Integer, >= 0).

end

Last loadcase (load step) to use from this analysis for rainflow counting. If omitted or 0, defaults to the

last loadcase analyzed. (Integer, >= 0).

interval

Interval between loadcases to use. If omitted or 0, defaults to 1. (Integer, >= 0).

Notes

1. If an optional value is specified, all preceding optional values must also be specified.

2. The ANSYS job identification name is formed by packing the structure name given in the preliminary

STRUCTURE command with the position of the job in the job name list file specified in the ANSYS

command. For example, ABCD18 means that the structure name is ABCD and the relevant job is the

18th one in the list of jobs that appear in the job name list file.

Examples

HIST 1 aaaa 1 1001 1HIST 2 bbbbHIST 3

4.20. INSET

The INSET command defines the position along a brace at which the fatigue calculations are to be

computed. This is intended to account for moment back-off to the chord/brace interface.

Parameters

INSET

Keyword

joint

Joint number at which the brace is connected (Integer).

brace

User element number to which the inset is to apply (Integer).

value

Inset value, positive values corresponding to moving along the brace away from the joint. The value

should not be greater than the element length (Real).

Notes

1. The value of the inset is added to any offsets modelled in the analysis for this brace.

2. The value of the bending moment used in the fatigue calculation is normally that occurring at the

offset end of the brace element connected to the joint. This value can sometimes be reduced by



INSET

computing an adjusted bending moment at the chord/brace interface; that is, at a distance of D/2

from the brace element end, where D is the chord diameter.

3. The value of the bending moment will be computed by assuming that the member is subjected to a

uniformly distributed load, the magnitude of which is calculated from a difference in the end shears.

4. Use of this command to generate results well away from the nodal positions may provide misleading

fatigue lives due to the loading assumptions described in Note 3 above.

5. If design properties are given for the end of a brace at which an inset is defined, the properties will

apply to the inset location.

Examples

INSET 1000 1101 0.8

4.21. INSPECTION


4.21.1. INSPECTION Command (Tubular sections)

4.21.2. INSPECTION Command (Non-tubular sections)

4.21.1. INSPECTION Command (Tubular sections)

This INSPECTION command defines the inspection points on tubular sections at which fatigue calculations

are to be undertaken. Inspection points can either be generated or defined explicitly.

Parameters

INSPECTION

Keyword

ninsp

Number of inspection points to be generated (Integer).

ELEMENT

Keyword to indicate that a brace element list is to follow.

list

List of user brace element numbers to be assigned the inspection points (Integer).

ANGLE

Keyword to indicate that explicit inspection angles are to be defined.

joint

Joint number at which the brace being defined is connected (Integer).

brace

User element number to be assigned the inspection points (Integer).

theta

List of angles, measured in degrees from the saddle location (see below) (Real).

Notes



1. This command is optional. If omitted, or for elements not specified on INSPECTION commands, a default

of four inspection points will be generated corresponding to angles of 0, 90, 180 and 270 from the

primary saddle location (see Note 5 below).

2. If the ELEMENT keyword and associated list is omitted then the inspection points defined will apply

to all elements (unless overridden by explicit definitions for specific elements).

3. If inspection points are generated then they will be equi-spaced with the first point at 0 degrees

(primary saddle) and subsequent points with angles increasing by 360/ninsp. Thus if ninsp is 8 then

the following angles will be generated:

0 45 90 135 180 225 270 315

4. The ANGLE option allows any number of inspection points to be defined.

5. Generated and explicit angles are measured relative to a saddle location. The location of the saddle

and the relationship of other inspection points to this are shown below:

For details of how the axis system is determined see Tubular Joint Inspection Points (p. 35).

Examples

INSP 8INSPECTION 12 ELEMENT 5 TO 10INSPECTION ANGLE 200 2010 0.0 51.0 96.0 132.0

4.21.2. INSPECTION Command (Non-tubular sections)

This INSPECTION command defines the inspection points on non-tubular sections at which fatigue cal-

culations are to be undertaken. Inspection points can either be generated or defined explicitly.

Parameters

INSPECTION

Keyword

SYMM

Keyword to indicate that 4 symmetric inspection points are to be defined.



INSPECTION

POSN

Keyword to indicate that specific inspection points are to be defined.

y, z

Pair of ordinates defining a point on the beam section in local y and z directions (Real).

ELEMENT

Keyword to indicate that a brace element list is to follow.

list

List of user brace element numbers to be assigned the inspection points (Integer).

joint

Joint number at which the brace being defined is connected (Integer).

brace

User element number to be assigned the inspection points (Integer).

Notes

1. If sections have been utilized in the analysis the program will default to four inspection points as

shown in Section Profile Information (p. 115). The use of the INSPECTION command may be used to

overwrite this default.

2. The SYMM option generates 4 points as follows:

3. The POSN option allows any number of inspection points to be defined.

4. No checks are carried out to ensure that the inspection point ordinates lie within the section (if defined).

Examples

INSPECTION SYMM 0.4 0.3INSPECTION SYMM 425.0 250.0 ELEMENT 5 TO 10INSPECTION POSN 200 2010 0.5 0.3 -0.5 0.3

4.22. JOB

The JOB command is used to define the type of analysis for the current run.

The JOB command is a preliminary command, and should only appear at the head of the FATJACK

data set.

Parameters



JOB

Keyword

POST

Keyword indicating post-processing of an analysis.

Usage

Compulsory.

Examples

JOB POST

4.23. JOINT

The JOINT command is used to select the joints at which the fatigue lives are to be computed. FATJACK

will generate a list of valid brace elements that are connected to the selected joints.

Parameters

JOINT

Keyword

nodelist

User list of node numbers which equate to the required joints. Keywords ALL and TO may be utilized

if required (Integer).

Usage

Compulsory.

Notes

1. This command is compulsory and may be repeated as often as required to define the problem.

2. Braces connected to the joint which are not required in the fatigue calculation may be ignored using

the SECONDARY command.

3. Joints of K and KT configurations which have been modelled using two or three nodes require a refer-

ence node to define the joint. Only the reference node should be defined on the JOINT command.

For further details see Joint Selection (p. 33).

Examples

JOINT ALLJOINT 56 TO 66JOINT 104 107 116 235

4.24. LIMIT

The SCF generators utilize parametric equations which have been derived for a limited range of values

for the parameters involved. The limiting values defined below are built into FATJACK, but these may

be overwritten, at the user’s discretion, using one or more LIMIT commands.



LIMIT

Parameters

LIMIT

Keyword

calc

Alphanumeric defining the equation type to which this limit applies. Permitted values are:

• KUANG

• WORDSWORTH

• DS449

• EFTHYMIOU

limval

Keyword indicating parameter for which default applicability limit is to be overwritten (Alphanumeric).

Permitted values are:

• ALPHA

• BETA

• GAMMA

• TAU

• THETA

minval

Lower applicability limit for parameter limval (Real).

maxval

Upper applicability limit for parameter limval (Real).

Notes

1. Default applicability limits are as follows (using the standard parameter definitions):



2. For any joint for which one or more parameters lie outside the limit values the SCF values will be cal-

culated with the actual values of the parameters and then recalculated with the appropriate parameters

reset to the limit values. The highest SCF value thus obtained will be taken.

If influence functions are being employed, coefficients at both the actual parameter and limiting

value are computed and stored. The critical hot spot stress is then computed as the maximum

utilizing either the actual or limiting parameter coefficients.

Examples

LIMIT KUAN ALPHA 10.0 35.0LIMIT WORDSWORTH BETA 0.2 1.0

4.25. NEWSTRUCTURE

The NEWSTRUCTURE command is used to define a new structure name to be associated with the results

created by the current run.

The NEWSTRUCTURE command is a preliminary command, and should only appear at the head

of the FATJACK data set.

Parameters

NEWSTRUCTURE

Keyword

nsname

Structure name to be associated with the results being created by the current run in order to identify

these results from others in the project. nsname must be unique for this project (Alphanumeric, 4

characters).

Usage



NEWSTRUCTURE

Optional.

Notes

1. If the NEWSTRUCTURE command is omitted then nsname defaults to the name ASNN. However, since

the structure name must be unique within a project, the default must not be assumed more than once

if the project contains a series of restarts.

2. A STRUCTURE command is normally required in conjunction with NEWSTRUCTURE to define the

name of the existing structure.

4.26. OPTIONS

The OPTIONS command is used to define the control options for this run.

The OPTIONS command is a preliminary command, and should only appear at the head of the

FATJACK data set.

Parameters

OPTIONS

Keyword

option

Four character option name, or list of option names. The following options are available:

• INFL - Requests that SCF calculations employing the Efthymiou empirical formulations are to use

the load influence methodology (See Joint Selection (p. 33)).

• NOTR - Do not write results to the User Results Storage Database.

• REFL - If wave spreading has been requested (using the SPREAD command), this option will select

wave cases in the opposite quadrant to couple with the requested direction (that is, reflecting the

wave by 1800).

• SCFG - requests that a formatted SCF file is generated from any automatic SCF computations. No

fatigue life calculations will be undertaken. The SCFs will be written to filegs, where file is the 4

character file name associated with this run (see FILES).

• GOON - Proceed even after printed WARNINGS. This option allows the run to continue beyond the

data checks despite questionable data. It should only be used after a run in which the WARNINGS

have been noted and rejected as unimportant.

Usage

Optional.

Examples

OPTIONS INFL



4.27. PARAMETER

Program calculated values of most parameters for specific braces at a previously defined joint may be

overwritten using the PARAMETER command. This enables the user to calculate SCF values using

geometry.

Parameters

PARAMETER

Keyword

joint

Joint number to which the brace is connected (Integer).

param

Keyword indicating the parameter for which the calculated value is to be overwritten for SCF calculation.

Permitted values:

• ALPHA

• BETA

• GAMMA

• TAU

• THETA

pval

Value of parameter param to be used in SCF calculation (Real).

brace

Brace number for which parameter param is to be updated. This element must be connected to the

previously defined joint (Integer).

Examples

PARAMETER 1100 BETA 0.6 110010

4.28. PRINT

The PRINT command is used to select the type of results to be reported and the format of the report.

If omitted the default report is provided.

Parameters

PRINT

Keyword

report-item

Keyword identifying what information is to be reported. Valid names are:



PRINT

XCHECK

Requests printing of cross checking information of input data.

SCFE

Requests a separate table of SCF information.

BRIEF

Brief fatigue report consisting of one line per joint/brace pair.

DETAILED

Standard fatigue report. Results are grouped by joint and provides lives at the worst inspection point

for a given brace.

FULL

Expands the BRIEF or DETAILED reports to include results for all inspection points.

SCFP

Adds SCF information to the BRIEF or DETAILED reports.

USAGE

Adds usage factor information to the BRIEF or DETAILED reports.

SUMMARY

Creates a summary report of braces which fail the fatigue target life.

DAMW

Requests damage per wave or sea-state. This is in addition to any other fatigue reports requested.

OCUR

Selects printing of stress ranges versus occurrences for spectral and time history analysis.

OCRT

As OCUR but produces results from for each transfer function for spectral analysis.

OCRW

As OCRT but produces results for each wave spectrum for spectral analysis.

PEAK

Requests that the stress peak value (+ve or -ve) is reported in a stress history analysis.

RNGE

Requests that the stress range is reported in a stress history analysis.

Notes

1. BRIEF and DETAILED options cannot be requested together.

2. FULL, SCFP and USAGE must be used in combination with BRIEF or DETAILED.

3. For spectral analyses with OCUR/OCRT/OCRW a SIGM command must be provided to define the

sampling points for the table. All other options (except XCHE and SCFE) are ignored.

4. PEAK/RNGE are only valid for stress history analyses and are mutually exclusive.

5. DAMW and OCRT/OCRW may produce large amounts of information and should be used only for

selective fatigue runs.

6. PRINT commands are cumulative so required reports may be requested individually or on one or more

lines.

Examples

PRINT BRIEF FULL SCFP SUMMARYPRINT XCHECK DETAILED DAMW



4.29. PROJECT

The PROJECT command is used to define the project name for the current run.

The PROJECT command is a preliminary command, and should only appear at the head of the

FATJACK data set.

Parameters

PROJECT

Keyword

pname

Project name for current run (Alphanumeric, 4 characters, first character must be alphabetic).

Usage

Optional, if omitted project name defaults to ASAS.

Notes

1. All runs with the same project name access the same database. A project database consists of one

project file (with a file name consisting of the 4 characters of pname with the number 10 appended),

which acts as an index to other files created under this project, together with those other files.

Examples

PROJECT HIJK

4.30. REDUCTION

The REDUCTION command requests the use of the Marshall Reduction factor for brace side SCF values

computed using the Kuang equations.

Parameters

REDUCTION

Keyword

factor

Optional factor to be applied (Real).

Usage

Optional, and may be defined only once.

Notes



REDUCTION

1. If this command is omitted completely no brace side reduction will take place.

2. If the factor is omitted, a default value of 0.63 will be utilized (as suggested by API).

3. The resulting brace side SCF values will be given by:

SCFbrace = factor * SCFchord

Examples

REDUCTIONREDU 0.7

4.31. RESU

The RESU command is used to specify saving of results to the results database.

The RESU command is a preliminary command, and should only appear at the head of the FATJACK

data set.

Parameters

RESU: Keyword.

Notes

1. For the results database to be used in any post-processing run with the ASAS solvers a RESU command

must be included in the initial ASAS run to initialise the database.

Examples

RESU

4.32. SCF Definition

Stress concentration factors (SCFs) relate hot spot stresses to the nominal stresses in a member computed

from the axial forces and in-plane and out-of-plane bending moments. FATJACK provides facilities for

both defining explicit SCF values and for automatically generating the SCF values using one or more

established empirical formulations.

Explicit and generated SCF values may be mixed as necessary to achieve the desired result.

A summary of available commands is shown below with detailed descriptions given in the following

sections.



Note that if influence functions are used to compute the hot spot stresses for braces at a given joint,

it is not currently possible to override the computed influence terms with conventional SCFs. Any user

specified values will be ignored.

Table 4.4 Commands available for explicit SCF specification

DescriptionCommand

Specifies default SCF values for a given section typeSCF TUB DEFAULT

SCF WF DEFAULT

SCF RHS DEFAULT

SCF BOX DEFAULT

Specifies crown and saddle SCF values at specified joints for tubular bracesSCFJOINT

Specifies SCF values at specific angular inspection points for tubular bracesSCFANGLE

Specifies SCF values at all inspection points for non-tubular bracesSCFBRACE

Specifies SCF values at specific inspection points for non-tubular bracesSCFPOINT

Table 4.5 Commands available for automatic SCF specification

DescriptionCommand

Specifies default empirical equation(s) to be utilized for the SCF generationSCF AUTO DE-

FAULT

Specifies joints at which automatic computation of SCF values to be undertakenSCF AUTO JOINT

Specifies minimum values for the SCF components calculated in automatic

generation

SCFMINIMUM

Permits user defined applicability limits for the parameters utilized in automatic

SCF generation

LIMIT

Permits explicit definition of the parameters utilized in automatic SCF generation

for specific braces

PARAMETER

4.32.1. SCFANGLE Command

The SCFANGLE command defines stress concentration factors to be applied at specific inspection points

around a tubular brace. This is useful where a detailed joint analysis has been undertaken and explicit

SCF values are known.

Parameters

SCFANGLE

Keyword

joint




SCF Definition

brace

Brace user element number for which the SCF values are to be specified (Integer).

angle

Angle (in degrees) from inspection point 1 (Real).

bscfa

Brace side SCF for axial force (Real).

bscfip

Brace side SCF for in-plane bending (Real).

bscfop

Brace side SCF for out-of-plane bending (Real).

cscfa

Chord side SCF for axial force (Real).

cscfip

Chord side SCF for in-plane bending (Real).

cscfop

Chord side SCF for out-of-plane bending (Real).

Notes

1. If only bscfa is specified, this value will be adopted for all six SCF values.

2. If SCFANGLE is used for a brace, results will only be computed at those inspection points explicitly

defined by the angles provided in the SCFANGLE commands. Any INSPECTION commands referring

to this brace end will be ignored. This implies that the SCF values at ALL inspection points need to be

provided. Where crown and saddle SCF values are known, use should be made of the SCFJOINT

command.

3. For any given brace, SCFANGLE and SCFJOINT are mutually exclusive and cannot be used together

in the same run of FATJACK.

Examples

SCFA 1100 110010 45.0 3.5 5.0 5.0 3.5 5.0 5.0SCFANGLE 85 1185 90.0 4.5

4.32.2. SCF AUTO DEFAULT Command

The SCF AUTO DEFAULT command defines the default generic empirical formulations to be used when

calculating the SCFs to be applied. The equations may be specified for given locations and stress com-

ponents thus permitting the use of the most appropriate formulation. Joints at which automatic SCF

computations are to be undertaken should be specified using the SCF AUTO JOINT command.

Parameters

SCF

Keyword

AUTO

Keyword



DEFAULT

Keyword

GENERAL

Keyword to denote that the equation matrix is applied to all joint types (unless overwritten).

type

Joint type to which this default matrix is to be applied (Alphanumeric). Valid joint types are:

• T

• Y

• K

• X

• KT

matrix

Defines the empirical formulations to be adopted for the following stress components and locations:

• Brace side axial crown

• Brace side axial saddle

• Brace side in-plane bending

• Brace side out-of-plane bending

• Chord side axial crown

• Chord side axial saddle

• Chord side in-plane bending

• Chord out-of-plane bending

The matrix consists of a series of characters representing the equation type to be used for each of

the stress components and locations above. Valid options are:

W

Wordsworth

K

Kuang

D

DS449

E

Efthymiou

Notes

1. Specific joint type definitions override those given by GENERAL commands.

2. If only one value is provided then this will be used for all stress components and locations. Either one

or eight equation identifiers must be defined.

3. If influence functions are employed then only Efthymiou equations may be requested. Other equation

types will produce an error.

Examples

SCF AUTO DEFA GENE K K W W K K W WSCF AUTO DEFAULT KT E



SCF Definition

4.32.3. SCF AUTO JOINT Command

The SCF AUTO JOINT command is used to request the joints at which automatic computation of SCF

values is to be undertaken. The equations to be used may be specified if they differ from those given

in the default definitions.

Parameters

SCF

Keyword

AUTO

Keyword

JOINT

Keyword

matrix

Defines the empirical formulations to be adopted for the following stress components and locations for

the braces connected to the specified jointlist:

• Brace side axial crown

• Brace side axial saddle

• Brace side in-plane bending

• Brace side out-of-plane bending

• Chord side axial crown

• Chord side axial saddle

• Chord side in-plane bending

• Chord out-of-plane bending

The matrix consists of a series of characters representing the equation type to be used for each of

the stress components and locations above. Valid options are:

W

Wordsworth

K

Kuang

D

DS449

E

Efthymiou

jointlist

List of joints at which automatic SCF generation is to be undertaken. Keywords ALL and TO may be

generate lists of joints (Integer).

Notes



1. If the matrix is omitted the default matrices for the brace configurations occurring at the specified

joint will be adopted.

2. If the matrix is specified it will be used for all braces connected to the specified joints irrespective of

the brace configurations.

3. If only one value is provided for the matrix then this will be used for all stress components and locations.

If any locations are different then all eight equation identifiers must be defined.

4. If influence functions are employed then only Efthymiou equations may be requested. Other equation

types will produce an error.

Examples

SCF AUTO JOINT ALLSCFANGLE 85 1185 90.0 4.5SCF AUTO JOIN E 10 TO 25SCF AUTO JOIN K K W W K K W W 100 200 300

4.32.4. SCFBRACE Command

The SCFBRACE command defines stress concentration factors to be applied at all inspection points for

non-tubular braces.

Parameters

SCFBRACE

Keyword

joint


brace


bscfa


bscfip


bscfop


cscfa


cscfip


cscfop


Notes




SCF Definition

2. SCF values defined will be applied at each of the inspection points defined using the INSPECTION

command. If different values are required at each inspection point the SCFPOINT command should

be used.

Examples

SCFB 100 1010 3.5SCFB 200 20200 4.0 4.5 4.5 4.0 4.5 4.5

4.32.5. SCF DEFAULT Command

The SCF DEFAULT command defines the default stress concentration factors to be applied to elements

of a given section type.

Parameters

SCF

Keyword

TUB, WF, RHS, BOX

Alphanumeric keyword defining type of section to which the default is to be applied.

DEFAULT

Keyword

bscfa

Default brace side SCF for axial force (Real).

bscfip

Default brace side SCF for in-plane bending (Real).

bscfop

Default brace side SCF for out-of-plane bending (Real).

cscfa

Default chord side SCF for axial force (Real).

cscfip

Default chord side SCF for in-plane bending (Real).

cscfop

Default chord side SCF for out-of-plane bending (Real).

Notes

1. This command is compulsory and must be defined only once for each section type that is to be pro-

cessed. The SCF value(s) specified will be adopted for any braces at joints which have not had specific

SCF values defined, or where automatic SCF calculation has not been requested.

2. If only bscfa is specified then this value will be adopted for all six SCF values.

Examples

SCF TUB DEFAULT 3.5SCF TUB DEFA 3.0 3.5 3.5 3.0 3.5 3.5



4.32.6. SCFJOINT Command

The SCFJOINT command is used to specify user defined crown and saddle SCF values for tubular braces

at specified joints. Selected locations may optionally adopt values computed from empirical SCF formu-

lations.

Parameters

SCFJOINT

Keyword

joint


brace


CHORD

Keyword to denote chord side SCF values are to be defined.

BRACE

Keyword to denote brace side SCF values are to be defined.

AUTO

Keyword to request that a computed value using the empirical formulations selected on an SCF AUTO

DEFAULT or SCF AUTO JOINT command is to be adopted.

axc

SCF for axial load, crown position (Real).

axs

SCF for axial load, saddle position (Real).

ipc

SCF for in-plane bending, crown position (Real).

ips

SCF for in-plane bending, saddle position (Real).

opc

SCF for out-of-plane bending, crown position (Real).

ops

SCF for out-of-plane bending, saddle position (Real).

Notes

1. If the AUTO keyword is used for any locations then a complementary SCF AUTO DEFAULT or SCF

AUTO JOINT command should be provided to define the method which is to be utilized for generating

the undefined values. This is also true if the chord or brace side definitions are completely omitted.

2. The ips and opc terms are strictly not required since the associated bending stress terms at these

locations are zero. They are used, however, if inspection points are selected at positions between the

saddle and crown locations. It is recommended, therefore, that the values are set the same for the

crown and saddle locations; that is ips set to ipc and opc set to ops. See SCF Interpolation (p. 39) for

details about the interpolation of SCF values at intermediate locations.



SCF Definition

3. For the SCF values to be correctly applied a chord must be identified for the joint concerned. This can

either be computed by the program, or may be specified using the CHORD command.

Examples

SCFJ 100 1010 CHORD 3.5 3.0 4.0 4.0 3.8 3.8SCFJ 100 1010 BRACE AUTO AUTO 4.2 4.2 4.15 4.15

4.32.7. SCFMINIMUM Command

The SCFMINIMUM command may be used to specify minimum values for the SCF components calculated

in the automatic SCF generation.

Parameters

SCFMINIMUM

Keyword

scfnam

Optional alphanumeric name indicating the SCF component for which the minimum SCF value is to be

specified. Permitted names are:

BAXS

Brace side axial saddle

BAXC

Brace side axial crown

BIPC

Brace side in-plane bending crown

BOPS

Brace side out-of-plane bending saddle

CAXS

Chord side axial saddle

CAXC

Chord side axial crown

CIPC

Chord side in-plane bending crown

COPS

Chord side out-of-plane bending saddle

scfmin

Minimum SCF (Real).

Notes

1. If scfmin is omitted then the SCF value defined will be adopted as a minimum for all SCF components

defined above.

2. The value(s) defined will only be applied to the SCF computations if they are appropriate to the

methodology adopted.



Examples

SCFM COPS 2.5SCFM 2.0

4.32.8. SCFPOINT Command

The SCFPOINT command defines stress concentration factors to be applied at specific inspection points

on non-tubular sections.

Parameters

SCFPOINT

Keyword

joint


brace


y, z

Pair of ordinates defining a point on the beam section in local y and z directions (Real).

bscfa


bscfip


bscfop


cscfa


cscfip


cscfop


Notes


2. If SCFPOINT is used for a brace, results will only be computed at those inspection points explicitly

defined by the ordinates provided in the SCFPOINT commands. Any INSPECTION commands referring

to this brace end will be ignored. This implies that the SCF values at ALL inspection points need to be

provided. Where SCF values are constant around the section, use should be made of the SCFBRACE

command.

3. For any given brace, SCFPOINT and SCFBRACE are mutually exclusive and cannot be used together

in the same run of FATJACK.

Examples



SCF Definition

SCFP 1100 110010 0.0 0.85 3.5 5.0 5.0 3.5 5.0 5.0SCFPOINT 85 1185 0.65 0.50 4.5

4.33. SECONDARY

The SECONDARY command is used to specify that certain elements are to be classified as secondary

members and omitted from the fatigue computations.

Parameters

SECONDARY

Keyword

ELEMENT

Keyword to denote selection by element number.

GROUP

Keyword to denote selection by element group number.

PROPERTY

Keyword to denote selection by geometric property number.

list

List of user element, group or geometric property numbers to which this data is to be assigned (Integer).

The list may include the keyword TO but not ALL.

Notes

1. Elements defined as secondary will not have fatigue calculations undertaken. Their effect will also be

ignored in joint classification for the purposes of SCF calculations and will not be included in influence

coefficient calculations.

Examples

SECO ELEM 100 TO 110SECO GROUP 999

4.34. SIGM

The SIGM command is required when stress range versus occurrence information has been requested

(using PRINT OCUR/OCRT/OCRW commands) and provides the additional information necessary to

generate the required table.

Parameters

SIGM

Keyword

peak

Peak stress range required (Real).



nint

Number of intervals to sample stress range (Integer).

Notes

1. This command is compulsory if PRINT OCUR/OCRT/OCRW has been requested.

2. Use of the PRINT OCUR/OCRT/OCRW commands requires that intervals of stress range are defined

over which the spectral information may be integrated to produce occurrence data for that range. The

interval of stress range is computed by dividing the peak value by the number of sampling intervals.

The mid value for each interval is then used as a reference value for that interval.

Examples

A data line of:

SIGM 1.0E6 5

will produce sampling points of:

1.0E5 3.0E5 5.0E5 7.0E5 9.0E5

Or graphically:

4.35. S-N

The S-N command assigns S-N curves (user or predefined) to brace elements to be analyzed.

Parameters

S-N

Keyword

name

Name of S-N curve to be assigned (Alphanumeric). This may either reference a standard S-N design curve

or a user defined curve (using the CURVE command).

END1, END2

Optional keywords to denote that the S-N curve is to be assigned to only one end of the element(s).



S-N

ELEMENT

Keyword to denote selection by element number.

GROUP

Keyword to denote selection by element group number.

list

List of elements or groups to which the S-N data is to be associated. (Integer.) Keywords ALL and TO

may be used to generate the list.

Notes

1. The following built in design curves are currently available:

Department of Energy T and F2 (in Air) curvesDET, DEF2

API RP2A X and X’ curvesAPX, APXD

Danish Offshore Regulations DS412 tubular curveDOT

2. If END1/END2 is omitted the curve is assigned to both ends of the brace element(s).

Examples

S-N APX ELEM 1000 TO 5000

4.36. SPECTRUM

The SPECTRUM command defines the wave spectrum probability information. The wave spectra are

assigned to a transfer function number which relates analyzed waves to a spectra by way of the

TRANSFER command. The sea state spectra may be supplied using predefined spectra or as user defined

ordinates on the wave energy spectrum diagram.

Parameters

SPECTRUM

Keyword.

itrans

Transfer function number (Integer).

SCTW

Keyword indicating Scott-Wiegel spectrum.

JONS

Keyword indicating JONSWAP spectrum (See Ref. 6).

PMOS

Keyword indicating Pierson-Moskowitz spectrum (See Ref. 5).



OCHI

Keyword indicating Ochi-Hubble spectrum (See Ref. 7).

UDEF

Keyword indicating user defined spectrum.

height

Significant wave height (Real).

period

Zero crossing period (Real).

prob

Probability (Real).

c1, c2

Constants used in defining Scott-Wiegel spectrum (Real).

hs1

Swell component significant wave height for Ochi-Hubble spectrum.

tp1

Swell component wave peak period for Ochi-Hubble spectrum.

peak1

Peakedness for swell component for Ochi-Hubble spectrum.

hs2

Wave component significant wave height for Ochi-Hubble spectrum.

tp2

Wave component wave peak period for Ochi-Hubble spectrum.

peak2

Peakedness for wave component for Ochi-Hubble spectrum.

strord

Stress direct spectral ordinate (input in the same order as the waves in the transfer function) (Real).

Notes

1. The units in which the probability is input (for example, occurrences per year, percentages, etc.) is

immaterial providing it is consistent for all the spectral data defined. The program computes a true

probability for each sea-state by dividing each input probability by the sum of all the probabilities.

2. Only one of SCTW, JONS, PMOS, OCHI or UDEF may be used in any one transfer function.

3. The Ochi-Hubble wave spectrum is bimodall; that is, it includes a swell and wave component.

4. For user defined spectra the frequency abscissae are extracted from the wave data defined for the

transfer function. The order of the stress ordinate data should be in increasing frequency of the wave

data assigned to this transfer function, including any additional frequencies defined.

Examples

Example of JONSWAP spectrum using three base wave cases:

TRANS 100 4 1.0 5 1.0 6 1.0SPEC 100 JONS 2.0 4.0 1.0SPEC 100 JONS 5.0 5.0 10.0SPEC 100 JONS 20.0 9.0 50.0

Example of user-defined spectrum using three base wave cases:



SPECTRUM

TRANS 10 10 1.1 11 1.12 12 1.09SPEC 10 UDEF 1.0 1.93 1.786 0.926SPEC 10 UDEF 10.0 12.79 7.23 2.86SPEC 10 UDEF 50.0 35.42 14.71 4.91

Example of Ochi-Hubble spectrum:

TRANS 5 10 1.0 11 1.0SPEC 5 OCHI 1.8 14.5 6.0 0.0 0.0 0.75 1.8SPEC 5 OCHI 0.9 12.5 6.0 0.3 5.5 0.75 2.1SPEC 5 OCHI 0.9 12.5 6.0 0.3 5.5 0.75 2.1

4.37. SPREADING

The SPREADING command requests that wave spreading should be applied.

Parameters

SPREADING

Keyword

power

Power of wave spreading function. If omitted, see notes for default values.

MITS

Requests Mitsuyasu spreading method. See Note 3(a).

MMIT

Requests modified Mitsuyasu spreading method. See Note 3(b).

GODA

Requests Goda spreading method. See Note 3(c).

Notes

1. The command is only valid for spectral analysis. If the command is omitted, no wave spreading calcu-

lations will be carried out.

2. Wave spreading is NOT permissible with the Ochi-Hubble wave spectrum.

3. Wave spreading calculations may be undertaken by any one of the three methods described below.

If SPREADING is supplied but no method is selected, MITS is used by default. Note that in all cases

the calculations are carried out on the stress transfer function squared.



(a) Mitsuyasu spreading method (See Ref. 8).

If MITS is requested then the Mitsuyasu wave spreading function is utilized, defined by:

(b) Modified Mitsuyasu spreading method (See Ref. 8).

If MMIT is requested then wave spreading calculations will be carried out using the modified Mitsuyasu

formula (based upon the complete wave environment) which is defined by:

(c) Goda spreading method (See Ref. 9).

If GODA is requested then wave spreading calculations will be carried out using the Goda formula

which is defined by:



SPREADING

For all three methods α is computed by the program by computing the angle between adjacent ana-

lysis waves. For example, for an analysis with wave directions in 45° increments, α will be 0.79 radians

and, for the default spreading, nw will be 5(-π/2 <= θ <= π/2). For Goda and Mitsuyasu nw will be 8(-π

<= θ <= π).

4.38. STOP

The STOP command is needed to signify the end of the data.

Parameters



STOP: Keyword.

4.39. STRUCTURE

The STRUCTURE command is used to define the name of an existing structure within the current project

which is to be processed in this run.

The STRUCTURE command is a preliminary command, and should only appear at the head of the

FATJACK data set.

Parameters

STRUCTURE

Keyword

sname

Structure name identifying which existing structure is to be accessed from the current project, see

PROJECT command (Alphanumeric, 4 characters, the first character must be alphabetic).

Usage

Compulsory.

Notes

1. See COMPONENT command.

Examples

STRUCTURE JACK

4.40. SYSTEM

The SYSTEM command is used to define the amount of memory used for data by this run.

The SYST command is a preliminary command, and should only appear at the head of the FATJACK

data set.

Parameters

SYSTEM

Keyword

DATA AREA

Keywords

memory

Amount of memory (in 4 byte words) to be used by this run. Typical values are between 30000 and

1000000. If the SYSTEM command is omitted, a default value of 1000000 is used. (Integer)



SYSTEM

Usage

Optional.

Examples

SYSTEM DATA AREA 80000

4.41. TEXT

The TEXT command is used to define a line of text to be printed once only at the beginning of the

output. Several TEXT lines may be defined to give a fuller description of the current analysis on the

printed output.

The TEXT command is a preliminary command, and should only appear at the head of the FATJACK

data set.

Parameters

TEXT

Keyword

text

This line of text will be printed once, at the beginning of the output (Alphanumeric, up to 75 characters).

Usage Optional.

Examples

TEXT THIS EXAMPLE OF THETEXT TEXT COMMAND IS SPREADTEXT OVER THREE LINES

4.42. THICKNESS

The THICKNESS command is used to request modification of the S-N curves to account for varying

plate thickness. S-N curves are generally specified for material thicknesses up to a given base value,

above this value the fatigue strength decreases with increasing thickness for a given level of stress

range. For built in S-N curves the base thickness is normally predefined (see below). For user defined

curves the base value must be supplied on the CURVE command.

Parameters

THICKNESS

Keyword



power

Power to be used in the thickness correction. If not defined the value defaults to 0.3 (in accordance with

the current Health and Safety Executive Guidance Notes).

Notes

1. This command may be defined only once. If omitted then no thickness correction will be undertaken.

2. The following base thicknesses are used for the built in S-N curves:

tbCurve

32 mmDET

22 mmDEF2

25 mmAPX

16 mmAPXD

N/ADOT

If the DOT S-N curve is being used, a base thickness must be supplied as part of the S-N data.

3. The correction has the effect of multiplying the stress range at an inspection point by the factor:

For all curve types except DET, t is set to be at least tb; that is, no reduction can occur. For the T

curve, t is set to be at least 22 mm; that is, a beneficial reduction is achieved for thicknesses

between 22 and 32 mm.

Examples

THICKTHICK 0.25

4.43. TITLE

The TITLE command is used to define a title for this run.

The TITLE command is a preliminary command, and should only appear at the head of the FATJACK

data set.

Parameters

TITLE

Keyword

title

This line of text will be printed out at the top of each page of FATJACK output (Alphanumeric, up to 74

characters).

Usage

Recommended.

Examples



TITLE

TITLE THIS IS AN EXAMPLE OF A TITLE LINE

4.44. TRANSFER

The TRANSFER command defines the constituent base wave cases for a given transfer function.

Parameters

TRANSFER

Keyword

itrans

Transfer function number (Integer).

case

Base wave case number for this transfer function. (Integer).

factor

Multiplying factor (dynamic amplification factor) to be applied to this base case (Real).

Notes

1. If additional frequencies are defined (using the FREQUENCY command) then these are automatically

included in the associated transfer function.

2. The command may be repeated as many times as is required to fully define the transfer function.

Examples

TRAN 5 10 1.09 11 1.12

4.45. TYPE

The TYPE command is used to predefine specific joint configurations for a given brace member (or

members) at a joint. This command is compulsory if joints are modelled with two or three nodes. The

configurations are used for the automatic computation of stress concentration factors.

Parameters

TYPE

Keyword

joint

Joint number at which the joint type is being defined (Integer).

type

Joint type (Alphanumeric). Valid joint types are:

• T



• Y

• K

• X

• KT

brace

User element number specifying a brace which is to be assigned this configuration. For KT joints this

must also be the central brace member (Integer).

brace2

Second user element number corresponding to the second brace in a K, X or KT joint (Integer).

brace3

Third user element number corresponding to the third brace of a KT joint (Integer).

Notes

1. For simple joints, modelled with a single node, this command is optional and if omitted the joint

configuration is automatically computed as T, Y, K, X or KT depending upon the chord brace geometry.

See Joint Classification (p. 34) for details.

2. If influence functions are used any additional braces connected to the joint will be included unless

declared as secondary.

Examples

TYPE 100 T 1000TYPE 250 KT 1100 1110 1120

4.46. UNITS

The UNITS command is used to define the UNITS which have been used in the previous analysis.

Parameters

UNITS

Keyword

unitnm

Name of unit to be utilized (see Notes).

Usage

The default units adopted for the input data will be those utilized in the original analysis and if this is

satisfactory no additional information is required in the FATJACK run.

If it is required to input any of the FATJACK data in a different system of units, this can achieved by

specifying one or more UNITS commands within the main body of the FATJACK data thus permitting

a combination of unit systems within the one data file.

Notes



UNITS

1. By default, the analysis units used in the previous analysis will be used.

2. If analysis units were not defined for the previous analysis, the units used MUST be specified here. If

analysis units were defined for the previous analysis, they can be reconfirmed here but cannot be

changed.

3. The UNITS command may be repeated throughout the data block thus permitting the greatest flexib-

ility in data input.

4. Force, length and angular unit may be specified. Only those terms which are required to be modified

need to be specified, undefined terms will default to those of the analysis global units unless previously

overwritten by another UNITS command. The default angular unit is degrees for all data types.

5. Analysis units must be defined if it is intended to use the UNITS command in the main FATJACK data.

Valid unit names are as follows:

MMETRE(S)Length

CMCENTIMETRE(S)

MMMILLIMETRE(S)

MICMMICROMETRE(S)

NANMNANOMETRE(S)

FTFOOT, FEET

ININCH, INCHES

NNEWTON(S)Force

KNKILONEWTON(S)

MNMEGANEWTON(S)

TNEFTONNEFORCE(S)

PDLPOUNDAL(S)

LBFPOUNDFORCE

KIPKIP(S)

TONFTONFORCE(S)

KGFKGFORCE(S)

Examples

To define or reconfirm the analysis units:

UNIT N M

To switch the length unit of the input data to millimetre:

UNIT MM

4.47. WAVE

The WAVE command defines the association between the analyzed load cases and the wave information

used to generate the loads. If the wave loading was generated by WAVE, the association may be extracted

automatically.



Parameters

WAVE

Keyword.

AUTO

Keyword to denote that wave information is to be extracted from the analysis files.

case

Wave case number associated with this wave data (Integer).

height

Wave height (Real).

period

Wave Period (Real).

direction

Wave direction (Real).

NPOS

Keyword to denote that the number of wave positions associated with this wave case is to be defined.

This is required for stress history analysis only.

npos

Number of wave positions associated with this wave case (Integer).

Notes

1. For wave loading generated or modified outside WAVE then the WAVE data must be supplied explicitly:

a. The WAVE commands must be specified in the order corresponding to the order of the analyzed

wave load cases.

b. The wave case numbers are independent of the load case numbers used in the analysis.

c. All wave cases analyzed must be defined.

2. For WAVE AUTO:

a. This command may only be used if the wave loading was generated using the WAVE program,

and no additional loading information was added prior to the analysis.

b. Loadcases will be generated sequentially from 1. For deterministic and spectral analyses there

will be one wave case for each analyzed load case pair. For stress history analysis due account

will be taken of the number of wave steps used in analysing each wave case.

Examples

WAVE 10 12.0 10.0 180.0WAVE 6 13.5 9.8 90.0 NPOS 8WAVE AUTO



WAVE

4.48. YEAR

The YEAR command defines the target fatigue life of the structure. Braces with fatigue lives less than

this value will be flagged as having failed.

Parameters

YEAR

Keyword

target

Target life in years (Real).

Examples

YEAR 50.0



Chapter 5: FATJACK Appendices


5.1. Running FATJACK

5.2. Section Profile Information

5.3. FATJACK References

5.1. Running FATJACK


5.1.1. ASAS Files Required by FATJACK

5.1.2. Files saved by FATJACK

5.1.1. ASAS Files Required by FATJACK

FATJACK operates on the RST files produced by a preceding Mechanical APDL analysis.

5.1.2. Files saved by FATJACK

If the RESU command is specified in the FATJACK data, then the results can be extracted (for example,

via AXL) or viewed graphically.

5.2. Section Profile Information

The following are the dimensional information required for each of the section types that may be specified

using a DESIGN command. For each section defined below, the four locations at which fatigue calculations

are undertaken are marked.

5.2.1. BOX - Symmetric Fabricated Box Section

Dimensional Properties: dbtf tw

where:



d

is the beam depth

b

is the beam width

tf

is the thickness of the ‘top’ and ‘bottom’ plates

tw

is the thickness of the ‘side’ plates

5.2.2. RHS - Rolled Hollow Section

Dimensional Properties: dbt

where:

d

is the beam depth

b

is the beam width

t

is the thickness

5.2.3. TUB - Tubes of Circular Section

Dimensional Properties: Dt



where:

D

is the outer diameter

t

is the wall thickness

5.2.4. WF - Wide Flanged Rolled I-Section

Dimensional Properties: dbtftw

where:

d

is the beam depth

b

is the flange width

tf

is the flange thickness

tw

is the web thickness

5.3. FATJACK References

Barltrop, N.D.P. & Adams, A.J., 1991, ‘Dynamics of Fixed Marine Structures’,

Third Edition.

Ref.

1

Wordsworth, A.C. & Smedley, G.P., 1978, ‘Stress concentrations at unstiffened

tubular joints’, European offshore steels research seminar.

Ref.

2

Kuang, J.G., Potvin, A.B., Leick, R.D., and Kahlich, J.L., 1977, ‘Stress concentration

in tubular joints’, Society of Petroleum Engineers Journal.

Ref.

3

Department of Energy, 1990, ‘Offshore Installations: guidance on design,

construction and certification’, 4th edition, HMSO.

Ref.

4

Pierson, W.J., and Moskowitz, L., 1964, ‘A proposed spectral form of fully de-

veloped wind seas based on the similarity theory of S.A. Kitaigorodskii’,

Journal of Geophysical Research, Volume69.

Ref.

5

Hasselmann, D.W., Dunckel, M. and Ewing, J.A., 1989, ‘Directional Wave Spectra

observed during JONSWAP in 1973’, Journal Physical Oceanography 10.

Ref.

6



FATJACK References

Ochi, M.K., 1976, ‘Proceedings of the 15th Coastal Engineering Conference’,

ASCE.

Ref.

7

Mitsuyasu, H. et al, 1975 ‘Observations of the directional spectrum of ocean

waves using a cloverleaf buoy’, Journal Physical Oceanography, Vol. 5.

Ref.

8

Goda, Y. and Suzuki, Y., 1975, ‘Computation of refraction and diffraction of

sea waves with Mitsuyasu’s directional spectrum’, Tech. Note of Port and

Harbour Research Institute No 230.

Ref.

9

DS449 Dansk Ingeniørforening 1984, ‘Pile-Supported Offshore Steel Structures’,

Part 2, AnnexE.

Ref.

10

Efthymiou, M. 1988, ‘Development of SCF formulae and generalised influence

functions for use in fatigue analysis’. OTJ’88.

Ref.

11



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