Transcript
Page 1: Mechanical FATJACK Users Manual

Mechanical FATJACK User's Manual

Release 16.0ANSYS, Inc.January 2015Southpointe

2600 ANSYS DriveCanonsburg, PA 15317 ANSYS, Inc. is

certified to ISO9001:2008.

[email protected]://www.ansys.com(T) 724-746-3304(F) 724-514-9494

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Copyright and Trademark Information

© 2014-2015 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, AIMand any and all ANSYS, Inc. brand, product, service and feature names, logos and slogans are registered trademarksor trademarks of ANSYS, Inc. or its subsidiaries in the United States or other countries. ICEM CFD is a trademarkused 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 productsand documentation are furnished by ANSYS, Inc., its subsidiaries, or affiliates under a software license agreementthat contains provisions concerning non-disclosure, copying, length and nature of use, compliance with exportinglaws, warranties, disclaimers, limitations of liability, and remedies, and other provisions. The software productsand documentation may be used, disclosed, transferred, or copied only in accordance with the terms and conditionsof 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 softwareand third-party software. If you are unable to access the Legal Notice, please contact ANSYS, Inc.

Published in the U.S.A.

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Table of Contents

1. FATJACK Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12. FATJACK Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.1. Fatigue Assessment .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32.2. S-N Curves .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32.3. Miner's Rule .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32.4. Deterministic Methods .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.5. Spectral Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52.6. Time History Methods .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.7. Strategies for Wave Fatigue Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.8. Parametric SCF Equations .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3. FATJACK Analysis Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353.1. Overview .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353.2. Environmental Information .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353.3. Joint Selection .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353.4. Joint Classification .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363.5. Inspection Points ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

3.5.1. Tubular Joint Inspection Points ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373.5.2. Tubular Butt Joints ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373.5.3. Non-Tubular Braces .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

3.6. Design Information .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393.6.1. Design Geometry .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393.6.2. Secondary Elements .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

3.7. Stress Concentration Factors ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393.7.1. Explicit SCF Definitions .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393.7.2. Empirical SCF Formulations .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403.7.3. Influence Functions .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403.7.4. SCF Interpolation .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413.7.5. Annotated SCF File Generation .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

3.8. S-N Curves .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433.9. Units ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433.10. Element Cross Sections .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433.11. Results presentation .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

3.11.1. Obtaining Results ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443.11.2. FATJACK Results ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

3.11.2.1. Fatigue Usage Factor Results ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443.11.2.2. Damage per Wave Results ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 453.11.2.3. Stress Range Results ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 453.11.2.4. Stress Histogram Results ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

4. FATJACK Command Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494.1. FATJACK Free Format Syntax .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

4.1.1. General Description .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 494.1.2. Special Symbols ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

4.2. FATJACK Priority of Data Assignments .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 534.3. Preliminary Data .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 544.4. Fatigue Analysis method .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

4.4.1. ANALYSIS command .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554.4.2. Deterministic Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

4.4.2.1. Deterministic Analysis Example .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 584.4.3. Spectral Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

4.4.3.1. Spectral Analysis Example .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

iiiRelease 16.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information

of ANSYS, Inc. and its subsidiaries and affiliates.

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4.4.4. Stress History Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 654.4.4.1. Stress History Analysis Example .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

4.4.5. Time History Analysis ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 694.4.5.1. Time History Analysis Example .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

4.5. ACCE .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 714.6. ALLOWABLE .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 724.7. ANSYS .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 724.8. CHORD ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 734.9. COMPONENT .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 754.10. CURVE .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

4.10.1. CURVE Command (User defined S-N curves) ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 764.10.2. CURVE Command (Base thickness definition for standard curves) ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

4.11. CYCLE .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 784.12. DESIGN .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 794.13. DETE .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 804.14. END .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 824.15. FILES .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 824.16. FREQUENCY .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 834.17. GAP .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 844.18. GAPDEFAULT .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 854.19. HIST .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 854.20. INSET .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 864.21. INSPECTION ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

4.21.1. INSPECTION Command (Tubular sections) ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 874.21.2. INSPECTION Command (Non-tubular sections) ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

4.22. JOB .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 904.23. JOINT .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 904.24. LIMIT .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 914.25. NEWSTRUCTURE .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 934.26. OPTIONS .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 934.27. PARAMETER .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 944.28. PRINT .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 954.29. PROJECT .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 964.30. REDUCTION ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 974.31. RESU .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 974.32. SCF Definition .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

4.32.1. SCFANGLE Command .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 994.32.2. SCF AUTO DEFAULT Command .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1004.32.3. SCF AUTO JOINT Command .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1024.32.4. SCFBRACE Command .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1034.32.5. SCF DEFAULT Command .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1044.32.6. SCFJOINT Command .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1054.32.7. SCFMINIMUM Command .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1064.32.8. SCFPOINT Command .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

4.33. SECONDARY .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1084.34. SIGM ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1094.35. S-N .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1104.36. SPECTRUM ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1114.37. SPREADING .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1134.38. STOP .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1154.39. STRUCTURE .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1164.40. SYSTEM ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

Release 16.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential informationof ANSYS, Inc. and its subsidiaries and affiliates.iv

FATJACK User's Manual

Page 5: Mechanical FATJACK Users Manual

4.41. TEXT .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1174.42. THICKNESS .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1174.43. TITLE .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1184.44. TRANSFER .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1194.45. TYPE .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1194.46. UNITS .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1204.47. WAVE .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1224.48. YEAR .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

5. FATJACK Appendices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1255.1. Running FATJACK .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

5.1.1. ASAS Files Required by FATJACK .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1255.1.2. Files saved by FATJACK .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

5.2. Section Profile Information .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1255.2.1. BOX - Symmetric Fabricated Box Section .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1255.2.2. RHS - Rolled Hollow Section .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1265.2.3.TUB - Tubes of Circular Section .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1265.2.4. WF - Wide Flanged Rolled I-Section .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

5.3. FATJACK References .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

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Chapter 1: FATJACK Introduction

FATJACK (FATigue calculations for offshore JACKets) is the fatigue calculation module. FATJACK is usedfor the estimation of fatigue life for tubular and beam joints, employing deterministic or spectralmethods.

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 withthe 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 secondarymembers

• 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 for-mulations

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

• 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-offvalue

• 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 Assessment2.2. S-N Curves2.3. Miner's Rule2.4. Deterministic Methods2.5. Spectral Analysis2.6.Time History Methods2.7. Strategies for Wave Fatigue Analysis2.8. Parametric SCF Equations

2.1. Fatigue Assessment

Steel members subjected to a sufficiently large fluctuating tensile stress will develop small crack-likedefects which may eventually lead to failure of the member, the crack becomes sufficiently large tocause 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, preventingthe inception of the initial defect. Offshore structures, however, are exposed to a mixture of large andsmall stress ranges making this approach impractical. It thus becomes necessary to design the structurefor a desired service life. The method used within FATJACK to carry out the fatigue assessment is basedupon the use of S-N curves.

2.2. S-N Curves

Tests of steel specimens subject to fluctuating loading demonstrate a relationship between the numberof 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 constantamplitude 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 ofthe 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 rangeof typical joints. Many codes of practice provide one or more standard S-N curves, some of which havebeen 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 whichpermits the fatigue assessment to be undertaken. Miner’s Rule is based upon the concept of fatiguedamage. For a given wave of constant amplitude the damage is given by:

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

Fatjack also calculates a usage figure, for easy comparison of results. This factor is based upon:

Usage = (DT)(1/S)

where:

D is the total damage

T is the target fatigue life

S is the slope of the S-N curve

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 ofloading cycles (or occurrences) in a year. The wave loading is generated (normally using MechanicalAPDL) to produce a series of loadcases which represent the waves for the required number of waveheights, periods and directions. The structure is then analyzed to determine the stress S for each of theloadcases and, hence, the fatigue life using Miner’s Rule.

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

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Under normal circumstances, where the structure responds sinusoidally to the load, the wave loadinggenerates a loadcase pair for each wave case analyzed. This pair of loadcases represents the real andimaginary parts of a solution which retains both magnitude and phase information. This is achieved byundertaking a harmonic wave analysis within Mechanical APDL. This approach is an efficient and effectiveway of determining the stress response of the structure to steady state harmonic loading. FATJACK usesthis 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), asinusoidal 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 todetermine explicitly the stress range. In this case Mechanical APDL is used to generate one or moreloadcases 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 stressrange is computed as twice the amplitude. For any other number of loadcases the stress range iscomputed as the difference between the maximum and minimum stress occurring within each of theconstituent 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 canbe obtained from the spectral method. The damage is accumulated at each inspection point throughoutthe frequency range, using the stress response spectrum at that point together with the appropriatematerial S-N characteristics.

For the purpose of sea state identification, wave direction is usually classified into eight sectors of 45°incidence angle bands (Figure 2.1: Sea states are applied by direction sector scatter diagrams (p. 6)).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 (Figure 2.2: A

scatter diagram summarizing the relative occurrence rate of individual sea state conditions for onedirection (p. 6)). The ratio of this number of occurrences to the total for all eight sector scatter diagramsgives the weighting to be applied later in determining the amount of fatigue damage due to each seastate.

In a particular random sea state, the instantaneous water surface elevation is considered to be causedby the combined effect of an infinite number of steady state components of wave frequency havingrandom 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 relationshipssuch 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 componentsthroughout the frequency range producing sea state spectra, Sηη (See diagram (a) in Figure 2.3: Random

Sea States (p. 6)).

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Figure 2.1: Sea states are applied by direction sector scatter diagrams

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

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stresses being normalized by the associated wave heights (See diagram (b) in Figure 2.3: Random SeaStates (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 Figure 2.3: Ran-dom Sea States (p. 6)).

Thus

Sσσ = Sηη*σ2

f

The fatigue damage incurred from one sea state at one stress inspection point is evaluated usingparameters from its stress response spectrum, the material fatigue data, Miner’s Rule and the relativerate of occurrence of that sea state, including the assumption that the peak stress levels are distributedaccording to a Rayleigh probability distribution (See diagram (d) in Figure 2.3: 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 annualdamage 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 solutionwhich provides an efficient method for carrying out the integration expression. For multi-linear S-Ncurves 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 numberof occurrences in a year. The structural response in the time domain is computed for each required seastate (normally by a transient analysis) to produce a series of stress time histories. FATJACK reads in theanalysis stress results to create a hot spot stress time history at each inspection location and utilizesthe rainflow counting method to produce a stress range histogram; that is, a table of number of cyclesvs. 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 followingdefines the required data and approach for various types of fatigue analysis:

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Strategies for Wave Fatigue Analysis

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NotesFATJACKAnalysis

Loadingrequirements

MechanicalAnalysis

Type

Rainflow counting for anumber of oceanenvironments

Time HistoryMultiple StressTime Histories

TransientStructural

Time HistoryDynamic

Use multiple load sets to geta stress range

StressHistory

Individual StressScenarios

Static StructuralTime HistoryDeterministicStatic

Use multiple load steps toget a stress range

StressHistory

Stress Time HistoryTransientStructural

Time HistoryDeterministicStatic

Ocean loading can begenerated using theHROCEAN, STATIC option

DeterministicReal & ImaginaryStresses

HarmonicResponse

HarmonicDeterministicStatic

Ocean loading can begenerated using theHROCEAN, STATIC option

SpectralReal & ImaginaryStresses

HarmonicResponse

Harmonic SpectralStatic

Ocean loading can begenerated using theHROCEAN, DYNAMIC option

SpectralReal & ImaginaryStresses

HarmonicResponse

Harmonic SpectralDynamic

The processes involved for various types of fatigue study when using the ANSYS Asas solver are sum-marized in Figure 2.4: Strategies for wave fatigue analysis using ANSYS Asas (p. 9).

Figure 2.5: Example of a time stress history fatigue analysis using ANSYS Asas (p. 10), Figure 2.6: Exampleof a harmonic deterministic fatigue analysis (static) using ANSYS Asas (p. 11), and Figure 2.7: Exampleof steady state dynamic spectral fatigue analysis using ANSYS Asas (p. 12) provide an overview of thecontrol data required to undertake the different fatigue analyses that are available in FATJACK. Fig-ure 2.8: Example of a time history fatigue analysis using ANSYS Asas (p. 13) shows the control data re-quired to undertake a time history fatigue analysis following a series of transient dynamic analyses.

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Figure 2.4: Strategies for wave fatigue analysis using ANSYS Asas

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

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

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

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Figure 2.8: Example of a time history fatigue analysis using ANSYS Asas

2.8. Parametric SCF Equations

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Parametric SCF Equations

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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 jointparameters within the following limits:

0.13 <= β <= 1.0

12 <= γ <= 32

0.25 <= τ <= 1.0

30° <= θ <= 90°

8 <= α <= 40

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Eqn. No.SCF EquationLoad Type

WT1Axial load

WT2

WT3 In-planebending

WT4 Out-of-planebending

Brace sideSCFs

Table 2.2: Wordsworth Equations For SCFs In X-joints

Eqn. No.SCF EquationLoad Type

WX1Axial load

WX2

WX3 In-planebending

WX4 Out-of-planebending(balanced)

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Eqn. No.SCF EquationLoad Type

Brace sideSCFs

Table 2.3: Wordsworth Equations For SCFs In K-joints

Eqn. No.SCF EquationLoad Type

Balancedaxial load

WK1

WK2

WK3

WK4

In-planebending

Out-of-planebending(unbalanced)

WK5

Brace sideSCF's

Table 2.4: Wordsworth Equations For SCFs In KT-joints

Eqn. No.SCF EquationLoad Type

Outer two braces only loaded.Balancedaxial load

Equations identical to those given for K joints may be used except thatg is the distance between the toes of the outer braces (gac).

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Eqn. No.SCF EquationLoad Type

WKT1 In-planebending

Unbalancedout-of-planebending

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. Cautionshould therefore be used when applying the equations to nodes wherethere is a large variation in brace dimensions.

Brace loadSCFs

Table 2.5: Kuang Equations In T/Y-joints

Validity Range

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

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Eqn. No.SCF EquationLoad Type

KT1Axial load

KT2

KT3In-planebending

KT4

KT5KT6

Out-of-planebending

KT7KT8

Table 2.6: Kuang Equations In K-joints

Eqn. No.SCF EquationLoad Type

KK1Axialload

KK2

KK3In-planebending

KK4

KK5Out-of-planebending

KK6

KK7KK8

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Table 2.7: Kuang Equations In KT-joints

Eqn. No.SCF EquationLoad Type

Axialload

KKT1

KKT2KKT3

KKT4

In-planebending

KKT5

KKT6

Out-of-planebending

KKT7 KKT8

KKT9KKT10

Table 2.8: Kuang Equations In T-joints

Eqn. No.SCF EquationLoad Type

Axial load

DT1

DT2

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Eqn. No.SCF EquationLoad Type

In-planebending

DT3

DT4

Out-of-planebending

DT5

DT6

Table 2.9: Danish Equations In Y-joints

Validity Range

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

Eqn. No.SCF EquationLoad Type

The following equations provide the basic SCF formulas for Yjoints. The code permits a reduction to be applied which isautomatically carried out by the program. The actual SCF valuecomputed is given by:

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Eqn. No.SCF EquationLoad Type

Axial load

DY1

DY2

In-planebending

DY3

DY4

DY5Out-of-planebending

DY6

DY7DY8

Table 2.10: Danish Equations In K and KT-joints

Eqn. No.SCF EquationLoad Type

The following equations provide the basic SCF formulas for K and KTjoints. The code permits a reduction to be applied which isautomatically carried out by the program. The actual SCF valuecomputed is given by:

Axial loadK-joints

DK1

DK2

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Eqn. No.SCF EquationLoad Type

Axial loadKT-joints

DKT1

DKT2

DKT3

In-planebending

DK3

DK4

Out-of-planebending

Table 2.11: Danish Equations In X-joints

Validity Range

The following Danish equations for X joints are generally validfor 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

Eqn. No.SCF EquationLoad Type

Axial load

DX1

DX2

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Eqn. No.SCF EquationLoad Type

In-planebending

DX3

DX4

Out-of-planebending

DX5

DX6

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

Validity Range

The following Efthymiou equations for T/Y joints are generallyvalid 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

ShortChordCorrection

Eqn.No.

SCF EquationLoad Type

If C < 0.8ET5Axial load -generalfixityconditions

F1 else F2

None

If C < 0.8F1 else F2

None

ET6

ET3

ET7

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ShortChordCorrection

Eqn.No.

SCF EquationLoad Type

NoneET8In-planebending

None ET9

F3ET10Out-of-planebending

F3 ET11

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

Table 2.13: Efthymiou Equations For SCFs In X-joints

Short ChordCorrection

Eqn.No.

SCF EquationLoad Type

If C < 0.8EX1Axial load

F1 else F2

None

If C < 0.8F1 else F2

None

EX2

EX3

EX4

NoneIn-planebending

None

F3EX5Out-of-planebending

F3EX6

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

Short ChordCorrection

Eqn.No.

SCF EquationLoad Type

Balanced axialload

None

None

EK1

EK2

Unbalancedin-planebending

EK3

Unbalancedout-of-planebending F4

F4

EK4

EK5

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

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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 ChordCorrection

Eqn.No.

SCF EquationLoad Type

Balanced axialload

In-planebending

Out-of-planebending

F4

F4

EKT1

EKT2

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

Short ChordCorrection

Eqn.No.

SCF EquationLoad Type

If C < 0.8EX7Axial load onreferencebrace only F1 else F2

If C < 0.8F1 else F2

EX8

F3Out-of-planebending onreferencebrace 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-planebending

EIX5

EIX6

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Note that in the above expressions subscript A refers to the reference brace, subscript B to the interactingbrace under consideration.

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

Short ChordCorrection

Eqn.No.

SCF EquationLoad Type

If C < 0.8 F1 else F2Axial load onone braceonly

None

If C < 0.8 F1 else F2

None

If no braces are present on the opposite side of the chord,βm = 0

NoneIn-planebending onone braceonly

None

Out-of-planebending onone braceonly

F3

F3

EK6

EK7

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Note that in the above expressions subscript A refers to the reference brace, subscript B to the interactingbrace under consideration.

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-planebending

EIK5

EIK6

Eqn. No.Influence function for brace ALoad Type

Axial load

EIK1

EIK2

EIK3

EIK4

Out-of-planebending

EIK5

EIK6

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Note that in the above expressions subscript A refers to the reference brace, subscript B to the interactingbrace under consideration.

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

Eqn. No.SCF EquationLoad Type

Axial load onreferencebrace only

Out-of-planebending onreferencebrace only

EKT3

EKT4

Eqn. No.SCF EquationLoad Type

Axial loadon referencebrace only

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Eqn. No.SCF EquationLoad Type

Out-of-planebending onreferencebrace only

EKT3

EKT4

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Table 2.21: Efthymiou Influence Functions For KT-joints

Eqn. No.Influence function for brace ALoadType

Axial

EIKT1

EIKT2

EIKT3

EIKT4

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Table 2.22: Efthymiou Hot-Spot Stresses In KT-joints

Eqn. No.Hot spot stress expressionLoad Type

Out-of-planebending

EIKT5

EIKT6

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Chapter 3: FATJACK Analysis Methods

This section discusses the following topics:3.1. Overview3.2. Environmental Information3.3. Joint Selection3.4. Joint Classification3.5. Inspection Points3.6. Design Information3.7. Stress Concentration Factors3.8. S-N Curves3.9. Units3.10. Element Cross Sections3.11. Results presentation

3.1. Overview

Fatigue analyses can require large amounts of data due to the methods employed in determining thehot spot stresses from the nominal brace loads. In addition, the mathematical model is often greatlysimplified especially at joints where brace center-lines are assumed to pass through a common pointand where stub and/or can details have been omitted.

FATJACK includes an extensive command set which enables the user to automatically generate muchof the required data and provides methods for developing a more precise definition of the problemthan 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 thatare to be processed. FATJACK requires that wave height, period and direction are supplied for eachwave case that has been analyzed. For stress history analyses, it is also necessary for the program toknow 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 inMechanical APDL, FATJACK can automatically extract the wave information from the analysis databasefiles. It should be noted, however, that this facility is not available if the loading has been modified inany 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 specificareas 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 whichhas valid elements connected is to be processed. Only BEAM and TUBE elements will be used by FATJACK,all other element types will be ignored.

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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 or3 nodes.

This is achieved using a combination of CHORD and TYPE commands. In these cases one of the nodesis 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 determinethe joint classification used for computing stress concentration factors for the brace connections to thejoint.

Unless otherwise defined (by using the CHORD command) the chord at a given joint is selected basedupon 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 willnot produce a unique chord definition; for example, at X joints with similar members, in which case thechord specification is compulsory. It should also be noted that where the chord elements are determinedby the program the chord length required for the stress concentration factor (SCF) calculations will becomputed as 2/3 times the combined lengths of the selected elements. This will produce erroneousSCFs if the chord elements selected do not completely define the chord member; for example, whereintermediate nodes have been included. Either all the elements which constitute the chord should bedefined, 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 groupsof elements that are in the same chord-brace plane. Within each plane a joint configuration is identifiedfor each brace end using the following classification table:

ClassificationNfarNnear

T/Y01

X11

T/Y21

T/Y31

Kany2

KTany3

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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±5o then the reference brace is designated as a T, otherwisethe joint is classified as a Y.

If the user wishes to assign joint classifications other than that provided by the program this can beachieved 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 selectedjoints. 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 ordinatesare 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 measuredrelative 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 localreference y axis. The local reference z axis forms a right handed set with the member axis and the localreference y axis. Note that, for consistency, the results are reported in terms of brace in-plane (y localaxis) 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 themembers connected to the joint. This is shown diagrammatically below:

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Inspection Points

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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 localreference y axis. The local reference z axis forms a right handed set with the member axis and the localreference y axis. Note that, for consistency, the results are reported in terms of brace in-plane (y localaxis) 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 tubularbutt joints. The inspection points are then defined by way of y and z ordinates (or in-plane bendingand 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 orientatedaway from the joint. The in-plane axis is in the same direction as the brace local y axis. The out-of-planeaxis forms a right handed set with the brace axis and the in-plane axis.

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3.6. Design Information

By default FATJACK utilizes the geometric and topology information that is stored in the ASAS fatiguemodel backing files. This information is used for computing both stress values and stress concentrationfactors (where requested).

There may be many instances when the data utilized for the structural analysis is inconsistent with thatrequired to undertake the fatigue study and FATJACK provides several mechanisms to override thevalues 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 andstress 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 propertiesto be defined. For non-tubular sections this is essential if sections have not been utilized in the originalanalysis in order that the appropriate SCF values may be utilized (see Stress Concentration Factors (p. 39)).

3.6.2. Secondary Elements

Since FATJACK is joint based, all valid elements connected to a joint will be processed. There may besituations where certain elements are not required for fatigue processing and these may be selectivelydeactivated by defining them as secondary elements. Note that the secondary elements are effectivelyremoved from the joint and thus will not be included in the joint classification and, hence, any automaticSCF evaluation that may be requested. Similarly secondary members will not be included in any influencefunction computations where this is operative (see Influence Functions (p. 40)).

3.7. Stress Concentration Factors

The damage calculations required for a fatigue analysis utilize the hot spot stresses at the inspectionpoints defined for a given brace. These hot spot stresses are normally determined from the bracenominal loads (axial force and lateral bending) and associated stress concentration factors for the locationsconcerned.

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 whenusing 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 formulaeby the user.

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SCFA if SCF values are known at specific locations; for example, results of a detailed finite elementjoint analysis, or from model tests.

• 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 theabsence of any explicit definitions or computed SCF values. Note that default SCF values are associatedwith 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 followingempirical 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, andposition around the brace/chord interface.

This facility enables brace elements at a joint to have SCF values computed at the crown and saddlelocations. 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 givenbrace member. This is achieved by specifying an equation matrix, the constituents of which define theformula to be adopted for each of the loading components and position. The user can thus utilize themost 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 totalflexibility in the determination of the SCF values, parameter definitions and limits may be modified usingthe PARAMETER and LIMIT commands.

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

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• In-plane bending in K joints is assumed balanced

For simple joints in a framed structure these assumptions are often reasonably valid and will providegood estimates of the structural behavior. For more complex joints, however, the load paths becomemuch 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 computingSCF values which are multiplied by the reference brace, but also generating influence terms which aremultiplied by loading in adjacent braces at the joint in question. The key principle involved in thismethodology is the superposition of linear elastic stress fields which enables a hot spot stress to becomputed 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 areutilized by including the INFL option in the preliminary data (without this option the conventional SCFvalues 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 valuesare computed (if requested). It is not currently possible to mix conventional SCFs (either explicitlydefined 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 byinterpolating 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 thesaddle, and the out-of-plane bending term at the crown. For automatically generated terms the followingconvention is adopted:

SCFips = SCFipc

SCFopc = SCFops

where:

ipsin-plane bending saddle

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ipcin-plane bending crown

opcout-of-plane bending crown

opsout-of-plane bending saddle

3.7.5. Annotated SCF File Generation

Since FATJACK is joint based, all valid elements connected to a joint will be processed. There may besituations where certain elements are not required for fatigue processing and these may be selectivelydeactivated by defining them as secondary elements. Note that the secondary elements are effectivelyremoved from the joint and thus will not be included in the joint classification and, hence, any automaticSCF evaluation that may be requested. Similarly secondary members will not be included in any influencefunction computations where this is operative (see Influence Functions (p. 40)).

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 *

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

equation (6)joint type*ascf values (6)SCFJ joint brace BRAC

equation (6)*ascf values (6)SCFJ joint brace CHORaequation (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 parameterswere exceeded for the given location and the value corresponding to the computed parameters arereported. 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 curvesconsist of linear or bi-linear relationships between log (S) and log (N). FATJACK enables S-N data to bedefined by reference to a library of S-N design curves from various recognized sources viz:

Department of Energy T curveDepartment of Energy F2 curveAmerican Petroleum Institute X curveAmerican Petroleum Institute X’ curveDanish 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 fatiguestrength 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 alwaysdefined 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 systemswithin 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 thesection data.

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3.11. Results presentation

Results can be viewed within the Mechanical application if using a Design Assessment system with theFATJACK Assessment Type. By default the results will also be output to a text file of the same name asthe input file, having the .out extension. The type and format of the results to be presented in thisfile is determined using the PRINT command. A number of options exist that permit a wide variety ofinformation to be reported with as much or as little detail as required. These are set based upon inputdata if using FATJACK through a Design Assessment system.

Results can also be obtained dynamically as described in the following sections:3.11.1. Obtaining Results3.11.2. FATJACK Results

3.11.1. Obtaining Results

FATJACK results can be brought into Excel using a custom plugin or can be accessed through Pythonfunctions. See Accessing Results using Excel in the Mechanical BEAMST User's Manual and AccessingResults using Python in the Mechanical BEAMST User's Manual for more information.

3.11.2. FATJACK Results

The results saved by FATJACK are dependent on the type of fatigue analysis carried out and the optionsselected for the run. This section discusses the following types of results:

3.11.2.1. Fatigue Usage Factor Results3.11.2.2. Damage per Wave Results3.11.2.3. Stress Range Results3.11.2.4. Stress Histogram Results

3.11.2.1. Fatigue Usage Factor Results

Fatigue usage factor results are stored under results type FATJACK USAGE. The results are stored on anumber of surfaces, with each surface representing an inspection point. The results are stored as elementresults on result set 1 and subset 0. Results components are as tabulated below. Components marked* are stored as character strings:

DESCRIPTIONRESULTSCOMPONENT

No of inspection pointsNO.INSPP

Inspection point numberINSP.PNT

First chord numberCHORD1

Second chord numberCHORD2

Joint type *JT.TYPE

Chord/brace *CHD/BRC

S-N table name *S-N

Failure flag *FAIL

Chord diameterCHOR.DIA

Chord thicknessCHOR.THK

Chord lengthCHOR.LEN

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DESCRIPTIONRESULTSCOMPONENT

Chord fixityCHOR.FIX

Brace diameterBRAC.DIA

Brace thicknessBRAC.THK

Inset (TUBE)INSET

Inspection point angle (TUBE)ANGLE

Y coordinate of point on section (non-TUBE)Y-COOR

Z coordinate of point on section (non-TUBE)Z-COOR

Brace axial SCFSCF.AXBR

Brace in-plane SCFSCF.IPBR

Brace out-of-plane SCFSCF.OPBR

usChord axial SCFSCF.AXCH

Chord in-plane SCFSCF.IPCH

Chord out-of-plane SCFSCF.OPCH

Usage factorUSAGE

Fatigue lifeLIFE

3.11.2.2. Damage per Wave Results

If print option DAMW was selected in the FATJACK run then the following additional information isstored under results type DAMAGE PER WAVE. The results are stored as element results on result setLC and sub-set 0. For spectral analysis, LC = IWVSPC, where IWVSPC is the spectrum number (1 ≤ IWVSPC≤ NSPEC) and NSPEC is the number of spectra. For all other analysis types, LC =ICASE, where ICASE isthe user wave case number.

DESCRIPTIONRESULTSCOMPONENT

Joint numberJOINT

Brace numberBRACE

Wave numberWAVE

Chord/brace *CHD/BRC

Inspection point angle (TUBE elements)ANGLE

Damage per waveDAMAGE

Inspection point Y coord (BEAM elements)Y-COOR

Inspection point Z coord (BEAM elements)Z-COOR

3.11.2.3. Stress Range Results

These results are saved if options PEAK or RNGE are specified in the FATJACK data. If utilization factorshave been requested then stress utilization factors will be saved.

Results will be stored under one of the following results types as appropriate:

• SIGNED PEAK STRESS

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• PEAK STRESS UTILS

• STRESS RANGE

• STRESS RANGE UTILS

The results are stored as element results on result set 1 and sub-set IDETM, where IDETM is the systemdeterministic case number (1 ≤ IDETM ≤ NDETM) and NDETM is the number of deterministic cases.

The results are stored as element results on results set LC and sub set 0, where LC is the user wave casenumber.

Results components are as tabulated below. Components marked * are stored as character strings:

DESCRIPTIONRESULTSCOMPONENT

Joint numberJOINT

Brace numberBRACE

Wave numberWAVE

Chord/brace *CHD/BRC

Inspection point angle (TUBE elements)ANGLE

Inspection point Y coord (BEAM elements)Y-COOR

Inspection point Z coord (BEAM elements)Z-COOR

Signed peak stress or stress rangeSTRESS

Utilization factorUTILS

3.11.2.4. Stress Histogram Results

If option OCRW is specified in a spectral fatigue job, the following element results are saved underresult type OCCUR EACH WAVE. The results are stored on result set IWVSPC and sub-set ISUB, whereIWVSPC is the spectrum number (1 ≤ IWVSPC ≤ NSPEC) and NSPEC is the number of spectra, ISUB = 1for brace side results, and ISUB = 2 for chord side results (if they are also stored).

Components marked + are stored on a per interval basis and require an interval to be entered as theresult position when obtaining the values via the function axlgetelementex.

DESCRIPTIONRESULTSCOMPONENT

Number of spectraNO.WAVE

Spectrum numberWAVE

Number of transfer functionsNO.TRFUN

Transfer function numberTR.FUNC

Number of intervalsNO.INTVL

Inspection point angleANGLE

Occurrence for stress range interval 1OCURENCE+

If option OCRT is specified in a spectral fatigue job, the following element results are saved under resultstype OCCUR EACH TRANSFER. The results are stored on result set ITRANS and sub-set ISUB, where ITRANS

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is the user transfer function number, ISUB=1 for brace side results, and ISUB = 2 for chord side results(if they are also stored).

Components marked + are stored on a per interval basis and require an interval to be entered as theresult position when obtaining the values via the function axlgetelementex.

DESCRIPTIONRESULTSCOMPONENT

Number of transfer functionsNO.TRFUN

Transfer function numberTR.FUNC

Number of intervalsNO.INTVL

Inspection point angleANGLE

Occurrence for stress range interval 1OCURENCE+

If option OCRT is specified in a spectral fatigue job, the following element results are saved under resulttype RANGE HISTOGRAM. The results are stored on result set 1 and sub-set ISUB. For brace side results,ISUB=1. For chord side results (if they are also stored), ISUB=2.

Components marked + are stored on a per interval basis and require an interval to be entered as theresult position when obtaining the values via the function axlgetelementex.

DESCRIPTIONRESULTSCOMPONENT

Number of spectraNO.WAVE

Number of transfer functionsNO.TRFUN

Number of intervalsNO.INTVL

Inspection point angleANGLE

Total occurrenceTOTAL

Stress range for interval 1STRESS+

Occurrence for stress range interval 1OCURENCE+

If option OCUR is specified in a time history fatigue job, the following element results are saved underresult type RANGE HISTOGRAM. The results are stored on result set LC and sub-set ISUB, where LC isthe user time history case number, ISUB=1 for brace side results, and ISUB = 2 for chord side results (ifthey are also stored).

Components marked + are stored on a per interval basis and require an interval to be entered as theresult position when obtaining the values via the function axlgetelementex.

DESCRIPTIONRESULTSCOMPONENT

Number of time historiesNO.WAVE

Time history numberWAVE

Number of intervalsNO.INTVL

Inspection point angle (TUBE elements)ANGLE

Inspection point Y coord (BEAM elements)Y-COOR

Inspection point Z coord (BEAM elements)Z-COOR

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DESCRIPTIONRESULTSCOMPONENT

Stress range for interval 1STRESS+

Occurrence for stress range interval 1OCURENCE+

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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 pairof loadcases representing the real and imaginary parts of the applied cyclic loading. Mechanical APDLautomatically outputs pairs of loadcases if the harmonic option is selected. The term wave case is usedin the FATJACK data description to indicate which pair of cases is being referred to. For example, wavecase 2 refers to the 2nd wave analyzed using the harmonic option or the 3rd and 4th loadcase from astatic 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 ofthe commands required for each analysis type are given in the following sections.

4.1. FATJACK Free Format Syntax

This section discusses the following topics:4.1.1. General Description4.1.2. 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 thedata items can be found in the remainder of this chapter.

Each data item consists as follows

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Each horizontal branch represents a possible input instruction. Input instructions are composed ofkeywords (shown in UPPER-CASE), numerical values or alphanumerics (shown in lower-case) andspecial symbols. Each item in the list is separated from each other by a comma or one or more blankspaces.

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 areequivalent:

• 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 thecharacters +, -, / 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. 51)).

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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 completeset 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 bypassesthe appropriate item:

Some data lines require an integer or real list to be input whose length is variable. This is shown by ahorizontal arrow around the list variable(s):

Where one or more possible alternative items may appear in the list, these are shown by separatebranches 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 theline will not be interpreted. It may appear anywhere on the line, any preceding datawill be processed as normal. For example:

*

* THIS IS A COMMENT FOR THE WHOLE LINECASE 4 2.7 * THIS IS A COMMENT FOR PART OF A LINE

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Single quotes are used to enclose some text strings which could contain otherwiseinadmissible 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. Forexample:

STRUCTURE ’As used for design study’ STRU

A comma or one or more consecutive blanks will act as a delimiter between itemsin 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 maybe 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, omittednumerical values are zero.

A colon at the start of the line signifies that the line is a continuation from theprevious 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 commandis 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 isencountered in the secondary file.

When the end of the secondary file is reached, that file is closed and inputswitches back to the previous data file. If, however, an @ command is found inthe secondary file, input switches to yet another file. This process can continueuntil a maximum of 5 secondary files are open simultaneously.

For example

@[email protected]@[email protected]@spectral.dat

design.dat might then contain the lines

@[email protected]@[email protected]

finally

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type.dat contains the joint designation datadesi.dat contains the design geometry dataetc

4.2. FATJACK Priority of Data Assignments

There are a number of commands that allow element and element ‘step’ data to be assigned in termsof element, group or property numbers. These appear in the command syntax diagrams in the followingformat:

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.

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It should be noted that when step data is explicitly being defined it overrides any element assignmentseven if the step data is assigned to a group or property and the element data assigned to an individualelement. Thus in the following example:

COMMand .... data1 STEP 2 GROU 5COMMand .... data2 STEP 2 PROP 1COMMand .... 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 notstep 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, awarning 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, theproject name, structure and component names, file names and options to be used. It also defines whichfiles are to be saved for further processing.

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The preliminary data must contain at least a JOB, STRUCTURE and END command. Other commandsshould be used as appropriate.

4.4. Fatigue Analysis method

This section discusses the following topics:4.4.1. ANALYSIS command4.4.2. Deterministic Analysis4.4.3. Spectral Analysis4.4.4. Stress History Analysis4.4.5.Time History Analysis

4.4.1. ANALYSIS command

The ANALYSIS command selects the method of analysis to be utilized. This command must immediatelyfollow the preliminary data.

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Parameters

ANALYSISKeyword

DETERMINISTICKeyword to select a deterministic analysis.

SPECTRALKeyword to select a spectral fatigue analysis.

STRESS HISTORYKeyword 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 fol-lowing sections Deterministic Analysis (p. 56) to Time History Analysis (p. 69) summarize the availablecommands 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 explicitlyreference waves that have been analyzed; that is, referred to in the WAVE data, or may consist of wave heightoccurrences, in which case interpolation is carried out to obtain member forces for wave heights that havenot been analyzed. This second approach permits a limited number of waves to be structurally analyzedwhilst providing a much more detailed fatigue definition.

Deterministic Commands

NoteUsageDescriptionCommand

CSelects deterministic analysis methodANALYSISDETERMINISTIC

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NoteUsageDescriptionCommand

CSelects joints at which fatigue lives arecalculated

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 TUBDEFAULT

4CDefault SCF valueSCF RHSDEFAULT 4

4

C

C

Default SCF value

Default SCF valueSCF WFDEFAULT

SCF BOXDEFAULT

Default SCF equations to be used ingeneration

SCF AUTODEFAULT

SCF equations to be used at specific jointsSCF AUTOJOINT

SCF values at specific inspection points ontubular braces

SCFANGLE

User defined SCF values for non-tubularbraces

SCFBRACE

User defined saddle and crown SCFsSCFJOINT

Minimum SCF valuesSCFMINIMUM

SCF values at specific inspection points onnon-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

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NoteUsageDescriptionCommand

CTerminates data inputSTOP

Usage

CCompulsory 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 wasgenerated 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

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: 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:

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

• Transfer function definition. It is normal to assign all the analyzed waves for a given direction to a particulartransfer function. This is achieved using the TRANSFER command which also permits dynamic amplificationfactors to be applied. This is compulsory.

• Sea state spectra definition. For each transfer function a series of sea state spectra are defined using theSPECTRUM command. A variety of spectra are available viz:

Scott-WeigelJONSWAPPierson-MoskowitzOchi-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 availableincluding 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 alimited number of waves to be structurally analyzed whilst providing a more detailed fatigue definition andis particularly suitable for structures that respond linearly to increasing wave heights. This command is op-tional.

Table 4.1: Spectral Commands

NoteUsageDescriptionCommand

CSelects spectral analysis methodANALYSISSPECTRAL

CSelects joints at which fatigue lives are calculatedJOINT

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 DEFAULT

4CDefault SCF valueSCF RHS DEFAULT

4CDefault SCF valueSCF WF DEFAULT

4CDefault SCF valueSCF BOXDEFAULT

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NoteUsageDescriptionCommand

Default SCF equations to be used in generationSCF AUTODEFAULT

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

User defined saddle and crown SCFsSCFJOINT

Minimum SCF valuesSCFMINIMUM

SCF values at specific inspection points on non-tubularbraces

SCFPOINT

Requests S-N thickness correctionTHICKNESS

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

CTarget fatigue lifeYEAR

7Report optionsPRINT

CTerminates data inputSTOP

Usage

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

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

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

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4.4.3.1. Spectral Analysis Example

The data has the following characteristics:

• 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 1.2331

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SPEC 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 0.1413SPEC 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 14.9948

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SPEC 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 1.7757SPEC 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 0.2378

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SPEC 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 50.0PRIN XCHE DETA USAG SUMM SCFESTOP

4.4.4. Stress History 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 (DETM). This data may either explicitlyreference waves that have been analyzed; that is, referred to in the WAVE data, or may consist of wave heightoccurrences, in which case interpolation is carried out to obtain member forces for wave heights that havenot been analyzed. This second approach permits a limited number of waves to be structurally analyzedwhilst providing a much more detailed fatigue definition.

Table 4.2: Stress History Commands

NoteUsageDescriptionCommand

CSelects stress history analysis methodANALYSISSTRESSHISTORY

CSelects joints at which fatigue lives are calculatedJOINT

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

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NoteUsageDescriptionCommand

4CDefault SCF valueSCF TUBDEFAULT

4CDefault SCF valueSCF RHSDEFAULT

4CDefault SCF valueSCF WFDEFAULT

4CDefault SCF valueSCF BOXDEFAULT

Default SCF equations to be used in generationSCF AUTODEFAULT

SCF equations to be used at specific jointsSCF AUTOJOINT

SCF values at specific inspection points on tubular bracesSCFANGLE

User defined SCF values for non-tubular bracesSCFBRACE

User defined saddle and crown SCFsSCFJOINT

Minimum SCF valuesSCFMINIMUM

SCF values at specific inspection points on non-tubularbraces

SCFPOINT

Requests S-N thickness correctionTHICKNESS

Allowable stressALLOWABLE

5CUser defined S-N damage curve definitionCURVE

CWave occurrence dataDETE

6CS-N curve assignmentS-N

CTarget fatigue lifeYEAR

7Report optionsPRINT

CTerminates data inputSTOP

Usage

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

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

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

4.4.4.1. Stress History Analysis Example

The data has the following characteristics:

• 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 6

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WAVE 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 18

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DETERMINISTIC.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:

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

• 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

NoteUsageDescriptionCommand

CSelects time history analysis methodANALYSISTIMEHISTORY

CSelects joints at which fatigue lives are calculatedJOINT

CSpecifies time history information from analysisHIST

1Chord 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

2Requests Marshall ReductionREDUCTION

3CDefault SCF valueSCF TUBDEFAULT

3CDefault SCF valueSCF RHSDEFAULT

3CDefault SCF valueSCF WFDEFAULT

3CDefault SCF valueSCF BOXDEFAULT

Default SCF equations to be used in generationSCF AUTODEFAULT

SCF equations to be used at specific jointsSCF AUTOJOINT

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NoteUsageDescriptionCommand

SCF values at specific inspection points on tubular bracesSCFANGLE

User defined SCF values for non-tubular bracesSCFBRACE

User defined saddle and crown SCFsSCFJOINT

Minimum SCF valuesSCFMINIMUM

SCF values at specific inspection points on non-tubularbraces

SCFPOINT

Requests S-N thickness correctionTHICKNESS

User defined S-N damage curve definitionCURVE

CRainflow counting dataCYCLE

CWave occurrence dataDETE

CS-N curve assignmentS-N

CTarget fatigue lifeYEAR

4Report optionsPRINT

CTerminates data inputSTOP

Usage

CCompulsory command, but see notes below where applicable.

Notes

1. 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.

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

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

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

4.4.5.1. Time History 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 4.4: Example of Time History Analysis Data File

JOB POSTPROJECT T206STRUCTURE A206NEWSTRUCTURE N206TITLE FATJACK USER MANUAL EXAMPLE

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OPTIONS 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 7CURV 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

ACCEKeyword

gravityGravitational 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 overwrittenusing the ACCE command.

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

Examples

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ACCE

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ACCE 32.2

4.6. ALLOWABLE

The ALLOWABLE command is used to request that the computed stress value from a Stress HistoryAnalysis is compared with a target (limit) value when PRINT PEAK or PRINT RNGE is also requested. Ifthe command is used FATJACK will report a utilization factor rather than a direct stress.

Parameters

ALLOWABLE: Keyword.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 resultswill be obtained.

The ANSYS command is a preliminary command, and should only appear at the head of theFATJACK data set.

Parameters

ANSYSKeyword

FNAMEKeyword 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 associatedwith 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 theanalysis together.

youngsYoung's Modulus (Optional, Real).

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densityMaterial density (Optional, Real).

Usage

The command is mandatory if FATJACK is to be performed following a Mechanical APDL analysis andmust 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 analyzedin FATJACK.

ANSYS ANSYSJOB

2. The Mechanical APDL analysis information is contained in a job name file called Ansysfile.txt, whichreferences three Mechanical APDL jobs called Ansysjob1, Ansysjob2 and Ansysjob3 located in differentdirectories.

ANSYS FNAME Ansysfile.txt

The contents of file Ansysfile.txt are:

C:\AnsysAnalysis\Job1\Ansysjob1

C:\AnsysAnalysis\Job2\Ansysjob2

C:\AnsysAnalysis\Job3\Ansysjob3

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

CHORDKeyword

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

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CHORD

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memberUser element number defining a segment of the chord associated with the specified joint. If computedchord lengths are required then all the members defining the chord must be supplied (Integer).

LENGTHKeyword to indicate that the chord length is to follow.

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

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

paraChord 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 elementsare described below. In cases where the chord member is segmented, however, it is suggested that a chordcommand is supplied in order that the correct chord length is utilized in any automated SCF computations.

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-linearelements 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 thesecircumstances, 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 endfixity 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 toprovide the connectivity information between the nodes at the joint. For KT joints modelled with threenodes, the joint number must be the central node and the chord elements must connect the three bracestogether (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

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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 substructureanalysis.

The COMP command is a preliminary command, and should only appear at the head of the FATJACKdata set.

Parameters

COMPONENTKeyword

snameStructure name identifying which existing structure is to be accessed from the current project, see thePROJ command (Alphanumeric, 4 characters, the first character must be alphabetic).

treeThis is the path down the component tree from the given structure in sname to the component which isbeing 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 ispart of structure STRU:

COMP STRU CMP1 CMP2

4.10. CURVE

The CURVE command defines the relationship between stress range and number of cycles to failureused in computing the damage contribution of the applied wave loading.

Standard curves available within FATJACK do not need to be defined unless non-standard basethicknesses are required for thickness correction.

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

Parameters

CURVEKeyword

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

SINGLEKeyword to denote a single slope curve is being defined.

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

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

stress, cyclePoint lying on a given section of the S-N curve. For multi-linear curves the point must correspond to theintersect within the adjacent section. For limiting curves the point must correspond to the cut-off position(Real).

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

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

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

Notes

1. The requirement for the ordinates of user defined multi-linear S-N curves to be at the intersection of adjacentsections is that two pairs of ordinates will be the same, but with differing slopes. This can be seen in theinternal representations of DET and DEF2 design curves (which are both bi-linear).

2. The base thickness is used when thickness correction of the S-N curve is requested (using the THICKNESScommand). 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

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

Parameters

CURVEKeyword

curvePredefined 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 tubularcurve

DOT

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

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

Note

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

Default Base ThicknessSlopeCycleStress

(N/mm2)

TYPECurve

32mm3.01.0D752.63404MULTIDET

5.01.0D752.63404

22mm3.01.0D735.05366MULTIDEF2

5.01.0D735.05366

25mm4.382.0D834.94451LIMITAPX

16mm3.742.0D823.06045LIMITAPXD

N/A (see note 2)4.12.0D833.81812LIMITDOT

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

2. The base thickness is used when thickness correction of the S-N curve is requested (using the THICKNESScommand). For the predefined curves (with the exception of the DOT curve) a default base thickness isadopted unless otherwise overridden by the user. For the DOT curve, no default base thickness is availableand a user defined value must be provided if thickness correction is required.

Example

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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

CYCLEKeyword

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

sigmaxPeak stress range required. If zero or not specified, the peak is determined automatically from the stresstime history (Real, >=0.0).

sig1Stress 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 de-termined 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 notdefined.

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

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:

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: 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 accountfor 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

DESIGNKeyword

typeSection type (Alphanumeric). Valid profiles are:

TUBTube

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

RHSRectangular Hollow Section (RHS)

BOXFabricated Box Section

valuesValues defining the section dimensions appropriate to the section type. See Section Profile Informa-tion (p. 125) for details (Real).

STEPKeyword to indicate the step number is to follow.

istepStep number for non-prismatic elements. Values should either be 1 or the last step number for the element.Alternatively the keywords END1 or END2 may replace STEP istep.

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ELEMENTKeyword to denote selection by element numbers.

GROUPKeyword to denote selection by element group numbers.

PROPERTYKeyword to denote selection by geometric property integer.

listList of user element, group or geometric property numbers for which this data is to be assigned. The listmay 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 propertylist will be assigned the new section data.

3. See FATJACK Priority of Data Assignments (p. 53) for order of priority for ELEMENT/GROUP/PROPERTYlists.

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

Parameters

DETEKeyword

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

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

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HEIGHTKeyword to denote that the occurrence data is to be given in terms of a reference height for a given direc-tion.

heightReference wave height (Real).

directionReference wave direction (Real, degrees).

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

dafDynamic amplification factor.

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

pvalOccurrence 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 dynamicamplification 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 theoccurrence data without use of wave case numbers and permitting additional wave height data to bedefined that were not previously analyzed.

For a given wave direction each height defined on a DETE command is related to the associatedanalyzed wave cases for the same wave direction.

Stress values for the reference wave height are obtained by linear interpolation between adjacentwave heights. Stresses for reference wave heights which are below the lower limit of the analyzedwave 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 willbe obtained by linear extrapolation of the last two cases. This is shown diagrammatically below.

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Using this facility, all wave occurrence data may be defined by reference to the wave height, thusobviating 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 forall DETE commands. The units in which the probability is input are immaterial providing that they areconsistent throughout. The program computes a true probability for each history by dividing each inputprobability 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 FATJACKdata set.

Parameters

ENDKeyword

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 FATJACKdata set.

Parameters

FILESKeyword

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

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 withtwo 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 transferfunction is to be evaluated in spectral analyses.

Parameters

FREQUENCYKeyword

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

freq-listList of frequency values. (Real, Hertz).

Notes

1. The frequencies defined MUST lie between the maximum and minimum frequencies associated with theanalyzed wave load cases forming the transfer function.

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

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4.17. GAP

The GAP command allows specific gap information to be defined between pairs of braces forming Kand KT joints. For overlapping joints the through member is also defined.

Parameters

GAPKeyword

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

braceUser element number specifying a brace forming part of a K or KT configuration about which the gap isto be defined (Integer).

brace2Second user element number corresponding to the second brace (Integer).

gapUser defined gap between braces brace and brace2. For overlapping gaps this dimension should benegative (Real).

THRUKeyword to indicate that through brace information is to follow for overlapping braces. Only permissibleif gap is negative.

bracedBrace element number representing the through member. Must be either brace or brace2 defined in thiscommand (Integer).

Notes

1. If GAP is not specified for a given K or KT joint, the gap adopts the value specified in the GAPDEFAULTcommand. If the default gap dimension has not been defined the gap is computed based upon modelgeometry. Where gap dimensions are computed these may be reset during the SCF computations to preventthe 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 anegative gap value representing the length of the overlap. Under these circumstances, a through bracemust 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

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4.18. GAPDEFAULT

The GAPDEFAULT command is used to specify a default gap dimension to be used between pairs ofbraces forming K and KT joints where specific gaps have not been defined.

Parameters

GAPDEFAULTKeyword

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

WWordsworth

KKuang

DDS449

EEfthymiou

gapDefault gap dimension (Real).

Notes

1. If GAPDEFAULT is not specified and a specific gap value is not defined for a given pair of braces forminga K or KT joint, the gap dimension is computed based upon model geometry. Since joint geometry is oftensimplified computed gaps may lead to erroneous values of generated stress concentration factors.

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

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Parameters

HISTKeyword

caseWave history case number (Integer, > 0).

stru

• For ASAS – name of structure from which data is going to be obtained, structure must be in the sameproject as that specified in preliminary data. If omitted, defaults to structure name given in the prelim-inary 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).

startFirst system loadcase (load step) to use from this analysis for rainflow counting. If omitted or 0, defaultsto 1 (Integer, >= 0).

endLast loadcase (load step) to use from this analysis for rainflow counting. If omitted or 0, defaults to the lastloadcase analyzed. (Integer, >= 0).

intervalInterval 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 preliminarySTRUCTURE 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 thelist 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 becomputed. This is intended to account for moment back-off to the chord/brace interface.

Parameters

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INSETKeyword

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

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

valueInset value, positive values corresponding to moving along the brace away from the joint. The value shouldnot 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 offsetend of the brace element connected to the joint. This value can sometimes be reduced by computing anadjusted bending moment at the chord/brace interface; that is, at a distance of D/2 from the brace elementend, 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 uni-formly 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 fatiguelives 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 applyto the inset location.

Examples

INSET 1000 1101 0.8

4.21. INSPECTION

This section discusses the following topics: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 calculationsare to be undertaken. Inspection points can either be generated or defined explicitly.

Parameters

INSPECTIONKeyword

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ninspNumber of inspection points to be generated (Integer).

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

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

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

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

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

thetaList 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 defaultof four inspection points will be generated corresponding to angles of 0, 90, 180 and 270 from the primarysaddle location (see Note 5 below).

2. If the ELEMENT keyword and associated list is omitted then the inspection points defined will apply to allelements (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 (primarysaddle) and subsequent points with angles increasing by 360/ninsp. Thus if ninsp is 8 then the followingangles 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 andthe relationship of other inspection points to this are shown below:

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For details of how the axis system is determined see Tubular Joint Inspection Points (p. 37).

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

INSPECTIONKeyword

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

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

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

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

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

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

braceUser 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 shownin Section Profile Information (p. 125). The use of the INSPECTION command may be used to overwrite thisdefault.

2. The SYMM option generates 4 points as follows:

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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 FATJACKdata set.

Parameters

JOBKeyword

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

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Parameters

JOINTKeyword

nodelistUser list of node numbers which equate to the required joints. Keywords ALL and TO may be utilized ifrequired (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 theSECONDARY command.

3. Joints of K and KT configurations which have been modelled using two or three nodes require a referencenode to define the joint. Only the reference node should be defined on the JOINT command. For furtherdetails see Joint Selection (p. 35).

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 valuesfor the parameters involved. The limiting values defined below are built into FATJACK, but these maybe overwritten, at the user’s discretion, using one or more LIMIT commands.

Parameters

LIMITKeyword

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

• KUANG

• WORDSWORTH

• DS449

• EFTHYMIOU

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limvalKeyword indicating parameter for which default applicability limit is to be overwritten (Alphanumeric).Permitted values are:

• ALPHA

• BETA

• GAMMA

• TAU

• THETA

minvalLower applicability limit for parameter limval (Real).

maxvalUpper 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 calculatedwith the actual values of the parameters and then recalculated with the appropriate parameters reset tothe limit values. The highest SCF value thus obtained will be taken.

If influence functions are being employed, coefficients at both the actual parameter and limitingvalue are computed and stored. The critical hot spot stress is then computed as the maximum util-izing either the actual or limiting parameter coefficients.

Examples

LIMIT KUAN ALPHA 10.0 35.0LIMIT WORDSWORTH BETA 0.2 1.0

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4.25. NEWSTRUCTURE

The NEWSTRUCTURE command is used to define a new structure name to be associated with the resultscreated by the current run.

The NEWSTRUCTURE command is a preliminary command, and should only appear at the headof the FATJACK data set.

Parameters

NEWSTRUCTUREKeyword

nsnameStructure name to be associated with the results being created by the current run in order to identify theseresults from others in the project. nsname must be unique for this project (Alphanumeric, 4 characters).

Usage

Optional.

Notes

1. If the NEWSTRUCTURE command is omitted then nsname defaults to the name ASNN. However, since thestructure name must be unique within a project, the default must not be assumed more than once if theproject contains a series of restarts.

2. A STRUCTURE command is normally required in conjunction with NEWSTRUCTURE to define the nameof 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 theFATJACK data set.

Parameters

OPTIONSKeyword

optionFour 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 theload influence methodology (See Joint Selection (p. 35)).

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• 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 wavecases 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 fatiguelife calculations will be undertaken. The SCFs will be written to filegs, where file is the 4 character filename associated with this run (see FILES).

• GOON - Proceed even after printed WARNINGS. This option allows the run to continue beyond the datachecks despite questionable data. It should only be used after a run in which the WARNINGS have beennoted 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 beoverwritten using the PARAMETER command. This enables the user to calculate SCF values usinggeometry.

Parameters

PARAMETERKeyword

jointJoint number to which the brace is connected (Integer).

paramKeyword indicating the parameter for which the calculated value is to be overwritten for SCF calculation.Permitted values:

• ALPHA

• BETA

• GAMMA

• TAU

• THETA

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pvalValue of parameter param to be used in SCF calculation (Real).

braceBrace number for which parameter param is to be updated. This element must be connected to the pre-viously 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

PRINTKeyword

report-itemKeyword identifying what information is to be reported. Valid names are:

XCHECKRequests printing of cross checking information of input data.

SCFERequests a separate table of SCF information.

BRIEFBrief fatigue report consisting of one line per joint/brace pair.

DETAILEDStandard fatigue report. Results are grouped by joint and provides lives at the worst inspection pointfor a given brace.

FULLExpands the BRIEF or DETAILED reports to include results for all inspection points.

SCFPAdds SCF information to the BRIEF or DETAILED reports.

USAGEAdds usage factor information to the BRIEF or DETAILED reports.

SUMMARYCreates a summary report of braces which fail the fatigue target life.

DAMWRequests damage per wave or sea-state. This is in addition to any other fatigue reports requested.

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OCURSelects printing of stress ranges versus occurrences for spectral and time history analysis.

OCRTAs OCUR but produces results from for each transfer function for spectral analysis.

OCRWAs OCRT but produces results for each wave spectrum for spectral analysis.

PEAKRequests that the stress peak value (+ve or -ve) is reported in a stress history analysis.

RNGERequests 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 samplingpoints 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 selectivefatigue runs.

6. PRINT commands are cumulative so required reports may be requested individually or on one or morelines.

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 theFATJACK data set.

Parameters

PROJECTKeyword

pnameProject name for current run (Alphanumeric, 4 characters, first character must be alphabetic).

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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 projectfile (with a file name consisting of the 4 characters of pname with the number 10 appended), which actsas 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 valuescomputed using the Kuang equations.

Parameters

REDUCTIONKeyword

factorOptional factor to be applied (Real).

Usage

Optional, and may be defined only once.

Notes

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.

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The RESU command is a preliminary command, and should only appear at the head of the FATJACKdata set.

Parameters

RESU: Keyword.

Notes

1. For the results database to be used in any post-processing run with the ASAS solvers a RESU commandmust be included in the initial ASAS run to initialize the database.

Examples

RESU

4.32. SCF Definition

Stress concentration factors (SCFs) relate hot spot stresses to the nominal stresses in a member computedfrom the axial forces and in-plane and out-of-plane bending moments. FATJACK provides facilities forboth defining explicit SCF values and for automatically generating the SCF values using one or moreestablished 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 followingsections.

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 userspecified 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

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DescriptionCommand

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 AUTODEFAULT

Specifies joints at which automatic computation of SCF values to be undertakenSCF AUTO JOINT

Specifies minimum values for the SCF components calculated in automaticgeneration

SCFMINIMUM

Permits user defined applicability limits for the parameters utilized in automaticSCF generation

LIMIT

Permits explicit definition of the parameters utilized in automatic SCF generationfor specific braces

PARAMETER

4.32.1. SCFANGLE Command

The SCFANGLE command defines stress concentration factors to be applied at specific inspection pointsaround a tubular brace. This is useful where a detailed joint analysis has been undertaken and explicitSCF values are known.

Parameters

SCFANGLEKeyword

jointJoint number to which the brace is connected (Integer).

braceBrace user element number for which the SCF values are to be specified (Integer).

angleAngle (in degrees) from inspection point 1 (Real).

bscfaBrace side SCF for axial force (Real).

bscfipBrace side SCF for in-plane bending (Real).

bscfopBrace side SCF for out-of-plane bending (Real).

cscfaChord side SCF for axial force (Real).

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cscfipChord side SCF for in-plane bending (Real).

cscfopChord 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 definedby the angles provided in the SCFANGLE commands. Any INSPECTION commands referring to this braceend will be ignored. This implies that the SCF values at ALL inspection points need to be provided. Wherecrown 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 thesame 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 whencalculating 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 SCFcomputations are to be undertaken should be specified using the SCF AUTO JOINT command.

Parameters

SCFKeyword

AUTOKeyword

DEFAULTKeyword

GENERALKeyword to denote that the equation matrix is applied to all joint types (unless overwritten).

typeJoint type to which this default matrix is to be applied (Alphanumeric). Valid joint types are:

• T

• Y

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• K

• X

• KT

matrixDefines 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 ofthe stress components and locations above. Valid options are:

WWordsworth

KKuang

DDS449

EEfthymiou

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 oreight equation identifiers must be defined.

3. If influence functions are employed then only Efthymiou equations may be requested. Other equationtypes will produce an error.

Examples

SCF AUTO DEFA GENE K K W W K K W WSCF AUTO DEFAULT KT E

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4.32.3. SCF AUTO JOINT Command

The SCF AUTO JOINT command is used to request the joints at which automatic computation of SCFvalues is to be undertaken. The equations to be used may be specified if they differ from those givenin the default definitions.

Parameters

SCFKeyword

AUTOKeyword

JOINTKeyword

matrixDefines the empirical formulations to be adopted for the following stress components and locations forthe 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 ofthe stress components and locations above. Valid options are:

WWordsworth

KKuang

DDS449

EEfthymiou

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jointlistList of joints at which automatic SCF generation is to be undertaken. Keywords ALL and TO may be gen-erate lists of joints (Integer).

Notes

1. If the matrix is omitted the default matrices for the brace configurations occurring at the specified jointwill be adopted.

2. If the matrix is specified it will be used for all braces connected to the specified joints irrespective of thebrace 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 equationtypes 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 fornon-tubular braces.

Parameters

SCFBRACEKeyword

jointJoint number to which the brace is connected (Integer).

braceBrace user element number for which the SCF values are to be specified (Integer).

bscfaBrace side SCF for axial force (Real).

bscfipBrace side SCF for in-plane bending (Real).

bscfopBrace side SCF for out-of-plane bending (Real).

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cscfaChord side SCF for axial force (Real).

cscfipChord side SCF for in-plane bending (Real).

cscfopChord 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. 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 elementsof a given section type.

Parameters

SCFKeyword

TUB, WF, RHS, BOXAlphanumeric keyword defining type of section to which the default is to be applied.

DEFAULTKeyword

bscfaDefault brace side SCF for axial force (Real).

bscfipDefault brace side SCF for in-plane bending (Real).

bscfopDefault brace side SCF for out-of-plane bending (Real).

cscfaDefault chord side SCF for axial force (Real).

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cscfipDefault chord side SCF for in-plane bending (Real).

cscfopDefault 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 processed.The SCF value(s) specified will be adopted for any braces at joints which have not had specific SCF valuesdefined, 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 bracesat specified joints. Selected locations may optionally adopt values computed from empirical SCF formu-lations.

Parameters

SCFJOINTKeyword

jointJoint number to which the brace is connected (Integer).

braceBrace user element number for which the SCF values are to be specified (Integer).

CHORDKeyword to denote chord side SCF values are to be defined.

BRACEKeyword to denote brace side SCF values are to be defined.

AUTOKeyword to request that a computed value using the empirical formulations selected on an SCF AUTODEFAULT or SCF AUTO JOINT command is to be adopted.

axcSCF for axial load, crown position (Real).

axsSCF for axial load, saddle position (Real).

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ipcSCF for in-plane bending, crown position (Real).

ipsSCF for in-plane bending, saddle position (Real).

opcSCF for out-of-plane bending, crown position (Real).

opsSCF 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 AUTOJOINT command should be provided to define the method which is to be utilized for generating the un-defined 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 locationsare zero. They are used, however, if inspection points are selected at positions between the saddle andcrown locations. It is recommended, therefore, that the values are set the same for the crown and saddlelocations; that is ips set to ipc and opc set to ops. See SCF Interpolation (p. 41) for details about the inter-polation of SCF values at intermediate locations.

3. For the SCF values to be correctly applied a chord must be identified for the joint concerned. This can eitherbe 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 calculatedin the automatic SCF generation.

Parameters

SCFMINIMUMKeyword

scfnamOptional alphanumeric name indicating the SCF component for which the minimum SCF value is to bespecified. Permitted names are:

BAXSBrace side axial saddle

BAXCBrace side axial crown

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BIPCBrace side in-plane bending crown

BOPSBrace side out-of-plane bending saddle

CAXSChord side axial saddle

CAXCChord side axial crown

CIPCChord side in-plane bending crown

COPSChord side out-of-plane bending saddle

scfminMinimum SCF (Real).

Notes

1. If scfmin is omitted then the SCF value defined will be adopted as a minimum for all SCF componentsdefined above.

2. The value(s) defined will only be applied to the SCF computations if they are appropriate to the methodologyadopted.

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 pointson non-tubular sections.

Parameters

SCFPOINTKeyword

jointJoint number to which the brace is connected (Integer).

braceBrace user element number for which the SCF values are to be specified (Integer).

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

bscfaBrace side SCF for axial force (Real).

bscfipBrace side SCF for in-plane bending (Real).

bscfopBrace side SCF for out-of-plane bending (Real).

cscfaChord side SCF for axial force (Real).

cscfipChord side SCF for in-plane bending (Real).

cscfopChord 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 SCFPOINT is used for a brace, results will only be computed at those inspection points explicitly definedby the ordinates provided in the SCFPOINT commands. Any INSPECTION commands referring to thisbrace 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 thesame run of FATJACK.

Examples

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 secondarymembers and omitted from the fatigue computations.

Parameters

SECONDARYKeyword

ELEMENTKeyword to denote selection by element number.

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GROUPKeyword to denote selection by element group number.

PROPERTYKeyword to denote selection by geometric property number.

listList 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 ignoredin joint classification for the purposes of SCF calculations and will not be included in influence coefficientcalculations.

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 togenerate the required table.

Parameters

SIGMKeyword

peakPeak stress range required (Real).

nintNumber 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 overwhich the spectral information may be integrated to produce occurrence data for that range. The intervalof stress range is computed by dividing the peak value by the number of sampling intervals. The mid valuefor each interval is then used as a reference value for that interval.

Examples

A data line of:

SIGM 1.0E6 5

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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-NKeyword

nameName of S-N curve to be assigned (Alphanumeric). This may either reference a standard S-N design curveor a user defined curve (using the CURVE command).

END1, END2Optional keywords to denote that the S-N curve is to be assigned to only one end of the element(s).

ELEMENTKeyword to denote selection by element number.

GROUPKeyword to denote selection by element group number.

listList of elements or groups to which the S-N data is to be associated. (Integer.) Keywords ALL and TO maybe used to generate the list.

Notes

1. The following built in design curves are currently available:

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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 areassigned to a transfer function number which relates analyzed waves to a spectra by way of theTRANSFER command. The sea state spectra may be supplied using predefined spectra or as user definedordinates on the wave energy spectrum diagram.

Parameters

SPECTRUMKeyword.

itransTransfer function number (Integer).

SCTWKeyword indicating Scott-Wiegel spectrum.

JONSKeyword indicating JONSWAP spectrum (See Ref. 6).

PMOSKeyword indicating Pierson-Moskowitz spectrum (See Ref. 5).

OCHIKeyword indicating Ochi-Hubble spectrum (See Ref. 7).

UDEFKeyword indicating user defined spectrum.

heightSignificant wave height (Real).

periodZero crossing period (Real).

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probProbability (Real).

c1, c2Constants used in defining Scott-Wiegel spectrum (Real).

hs1Swell component significant wave height for Ochi-Hubble spectrum.

tp1Swell component wave peak period for Ochi-Hubble spectrum.

peak1Peakedness for swell component for Ochi-Hubble spectrum.

hs2Wave component significant wave height for Ochi-Hubble spectrum.

tp2Wave component wave peak period for Ochi-Hubble spectrum.

peak2Peakedness for wave component for Ochi-Hubble spectrum.

strordStress 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 imma-terial providing it is consistent for all the spectral data defined. The program computes a true probabilityfor 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 transferfunction. The order of the stress ordinate data should be in increasing frequency of the wave data assignedto 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:

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

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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

SPREADINGKeyword

powerPower of wave spreading function. If omitted, see notes for default values.

MITSRequests Mitsuyasu spreading method. See Note 3(a).

MMITRequests modified Mitsuyasu spreading method. See Note 3(b).

GODARequests 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 calculationswill 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. IfSPREADING is supplied but no method is selected, MITS is used by default. Note that in all cases the cal-culations are carried out on the stress transfer function squared.

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(a) Mitsuyasu spreading method (See Ref. 8).

If MITS is requested then the Mitsuyasu wave spreading function is utilized, defined by:

where:

nw is the number of waves in the range

n is the defined wave spreading power (default value is 4.0)Tn is the transfer function prior to wave spreading

Ts is the transfer function modified for wave spreading

θ is the angle of the wave d relative to the mean wave directionα is the angle over which the wave d is applied (radians)

Cn is the normalization function

(b) Modified Mitsuyasu spreading method (See Ref. 8).

If MMIT is requested then wave spreading calculations will be carried out using the modified Mitsuyasuformula (based upon the complete wave environment) which is defined by:

where:

nw is the number of waves in the range

n is the defined wave spreading power (default value is 4.0)Tn is the transfer function prior to wave spreading

Ts is the transfer function modified for wave spreading

θ is the angle of the wave d relative to the mean wave directionα is the angle over which the wave d is applied (radians)

Cn is the normalization function

(c) Goda spreading method (See Ref. 9).

If GODA is requested then wave spreading calculations will be carried out using the Goda formulawhich is defined by:

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where:

nw is the number of waves in the range

Tn is the transfer function prior to wave spreading

Ts is the transfer function modified for wave spreading

θ is the angle of the wave d relative to the mean wave directionα is the angle over which the wave d is applied (radians)

Cn is the normalization function

r is the equation

where:

rmax is the defined peak spreading power (default 10.0)

f is the frequencyfp if the frequency associated with the spectral peak

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 radiansand, 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.

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Parameters

STOP: Keyword.

4.39. STRUCTURE

The STRUCTURE command is used to define the name of an existing structure within the current projectwhich is to be processed in this run.

The STRUCTURE command is a preliminary command, and should only appear at the head of theFATJACK data set.

Parameters

STRUCTUREKeyword

snameStructure name identifying which existing structure is to be accessed from the current project, see PROJECTcommand (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 FATJACKdata set.

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Parameters

SYSTEMKeyword

DATA AREAKeywords

memoryAmount 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)

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 theoutput. Several TEXT lines may be defined to give a fuller description of the current analysis on theprinted output.

The TEXT command is a preliminary command, and should only appear at the head of the FATJACKdata set.

Parameters

TEXTKeyword

textThis 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 varyingplate 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

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range. For built in S-N curves the base thickness is normally predefined (see below). For user definedcurves the base value must be supplied on the CURVE command.

Parameters

THICKNESSKeyword

powerPower to be used in the thickness correction. If not defined the value defaults to 0.3 (in accordance withthe 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 between22 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 FATJACKdata set.

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Parameters

TITLEKeyword

titleThis line of text will be printed out at the top of each page of FATJACK output (Alphanumeric, up to 74characters).

Usage

Recommended.

Examples

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

TRANSFERKeyword

itransTransfer function number (Integer).

caseBase wave case number for this transfer function. (Integer).

factorMultiplying 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 in-cluded 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 (ormembers) at a joint. This command is compulsory if joints are modelled with two or three nodes. Theconfigurations are used for the automatic computation of stress concentration factors.

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TYPE

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Parameters

TYPEKeyword

jointJoint number at which the joint type is being defined (Integer).

typeJoint type (Alphanumeric). Valid joint types are:

• T

• Y

• K

• X

• KT

braceUser element number specifying a brace which is to be assigned this configuration. For KT joints this mustalso be the central brace member (Integer).

brace2Second user element number corresponding to the second brace in a K, X or KT joint (Integer).

brace3Third 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 configur-ation is automatically computed as T, Y, K, X or KT depending upon the chord brace geometry. See JointClassification (p. 36) for details.

2. If influence functions are used any additional braces connected to the joint will be included unless declaredas 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.

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Parameters

UNITSKeyword

unitnmName 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 issatisfactory 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 byspecifying one or more UNITS commands within the main body of the FATJACK data thus permittinga combination of unit systems within the one data file.

Notes

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 ana-lysis 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 flexibilityin data input.

4. Force, length and angular unit may be specified. Only those terms which are required to be modified needto be specified, undefined terms will default to those of the analysis global units unless previously overwrittenby 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. Validunit 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)

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UNITS

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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 informationused to generate the loads. If the wave loading was generated by WAVE, the association may be extractedautomatically.

Parameters

WAVEKeyword.

AUTOKeyword to denote that wave information is to be extracted from the analysis files.

caseWave case number associated with this wave data (Integer).

heightWave height (Real).

periodWave Period (Real).

directionWave direction (Real).

NPOSKeyword 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.

nposNumber of wave positions associated with this wave case (Integer).

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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 waveload 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 noadditional loading information was added prior to the analysis.

b. Loadcases will be generated sequentially from 1. For deterministic and spectral analyses there will beone wave case for each analyzed load case pair. For stress history analysis due account will be taken ofthe number of wave steps used in analyzing each wave case.

Examples

WAVE 10 12.0 10.0 180.0WAVE 6 13.5 9.8 90.0 NPOS 8WAVE AUTO

4.48. YEAR

The YEAR command defines the target fatigue life of the structure. Braces with fatigue lives less thanthis value will be flagged as having failed.

Parameters

YEARKeyword

targetTarget life in years (Real).

Examples

YEAR 50.0

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YEAR

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Chapter 5: FATJACK Appendices

This section discusses the following topics:5.1. Running FATJACK5.2. Section Profile Information5.3. FATJACK References

5.1. Running FATJACK

This section discusses the following topics:5.1.1. ASAS Files Required by FATJACK5.1.2. 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 specifiedusing a DESIGN command. For each section defined below, the four locations at which fatigue calculationsare undertaken are marked.

5.2.1. BOX - Symmetric Fabricated Box Section

Dimensional Properties: dbtf tw

where:

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dis the beam depth

bis 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:

dis the beam depth

bis the beam width

tis the thickness

5.2.3. TUB - Tubes of Circular Section

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Dimensional Properties: Dt

where:

Dis the outer diameter

tis the wall thickness

5.2.4. WF - Wide Flanged Rolled I-Section

Dimensional Properties: dbtftw

where:

dis the beam depth

bis 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 unstiffenedtubular joints’, European offshore steels research seminar.

Ref.2

Kuang, J.G., Potvin, A.B., Leick, R.D., and Kahlich, J.L., 1977, ‘Stress concentrationin 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

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Pierson, W.J., and Moskowitz, L., 1964, ‘A proposed spectral form of fullydeveloped 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 Spectraobserved during JONSWAP in 1973’, Journal Physical Oceanography 10.

Ref.6

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 oceanwaves using a cloverleaf buoy’, Journal Physical Oceanography, Vol. 5.

Ref.8

Goda, Y. and Suzuki, Y., 1975, ‘Computation of refraction and diffraction ofsea waves with Mitsuyasu’s directional spectrum’, Tech. Note of Port andHarbour 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 influencefunctions for use in fatigue analysis’. OTJ’88.

Ref.11

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