ABS 125 NOTICE 2-2017 GUIDE FOR SPECTRAL-BASED FATIGUE ANALYSIS FOR VESSELS JUNE 2016.pdf

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1、 GUIDE FOR SPECTRAL-BASED FATIGUE ANALYSIS FOR VESSELS JUNE 2016 NOTICE NO. 2 October 2017 The following changes were approved by the ABS Rules Committee on 4 October 2017 and become EFFECTIVE AS OF 1 OCTOBER 2017. (See http:/www.eagle.org for the consolidated version of the Guide for Spectral-Based

2、 Fatigue Analysis for Vessels, 2016, with all Notices and Corrigenda incorporated.) Notes - The date in the parentheses means the date that the Rule becomes effective for new construction based on the contract date for construction. (See 1-1-4/3.3 of the ABS Rules for Conditions of Classification (P

3、art 1).) FOREWORD (Revise Foreword, as follows.) Foreword (1 October 2017) This Guide provides information about the optional classification notations, Spectral Fatigue Analysis SFA (years) and SFA (years, WWT) which are available to qualifying vessels as described in 1-1-3/21 of the ABS Rules for C

4、onditions of Classification (Part 1). (Following text remains unchanged.) SECTION 1 INTRODUCTION 1 Purpose and Applicability (1 October 2017) (Revise Subsection 1/1, as follows.) Part 5C of the ABS Rules for Building and Classing Steel Vessels (Steel Vessel Rules) includes the fatigue assessment cri

5、teria for the classification of various types of specialized vessels covered by the Rules. Part 5A and 5B of the ABS Rules for Building and Classing Steel Vessels (Steel Vessel Rules) contains fatigue assessment guidance for vessels subject to the “Common Structural Rules for Bulk Carriers and Oil T

6、ankers”. A brief description of the background and objectives of these fatigue criteria is given in Subsection 1/3. In addition to the simplified fatigue strength criteria required for classification by ABS, the Owner may wish to apply more extensive Spectral-based Fatigue Analysis (SFA) techniques

7、to the vessels structural systems. It may be an added objective of these Spectral-based Fatigue Analyses to demonstrate a longer design fatigue life than that required for classification. ABSGUIDE FOR SPECTRAL-BASED FATIGUE ANALYSIS FOR VESSELS .2016 1 Notice No. 2 October 2017 Spectral-based Fatigu

8、e Analysis techniques are used in addition to the SafeHull Fatigue Assessment technique, a Permissible Stress Range method (discussed in Subsection 1/3). The fatigue life of each critical location in the structural system is assessed for adequacy. The critical locations are to be selected using the

9、results of the SafeHull Fatigue Assessment technique which is to be employed in the overall structural design and analysis effort. The list of critical structural locations which are to be subjected to Spectral-based Fatigue Analysis is to be submitted to ABS for approval. Provided that Spectral-bas

10、ed Fatigue Analysis is conducted in accordance with the procedures included in this Guide or equivalent, ABS will grant the optional classification notation, SFA (years) or SFA (years, WWT). In either case, as a minimum, a vessel is to meet the fatigue strength criteria in the Steel Vessel Rules as

11、described above. The SFA (years) notation is granted if the design fatigue life value is equal to 20 years or greater under the wave conditions of unrestricted service defined in Section 5, Table 1. The SFA (years, WWT) notation is granted if the design fatigue life value is equal to 40 years or gre

12、ater under the wave conditions of worldwide trading service defined in Section 5, Table 2. If a vessel is primarily operating in seas that exceed the worldwide trading pattern (i.e., a vessel operating half or more than half of its life in onerous seas including North Atlantic or North Pacific), SFA

13、 (years, WWT) is not applicable. It should be noted that the calculated fatigue lives for different design wave conditions may produce significantly different fatigue lives. The value in parentheses is the design fatigue life in years specified by the applicant in 5-year increments starting at 20 fo

14、r SFA (years) and 40 for SFA (years, WWT). The structural system as a whole is analyzed to verify that the calculated fatigue life values for the entire system meet or exceed the design fatigue life. The actual service life of a vessel is dependent on many factors such as initial design, operational

15、 and maintenance schemes. The SFA (years) or SFA (years, WWT) notation denotes the design fatigue life of a vessel and is not a guarantee that the vessel or structure will achieve the design fatigue life. In order to obtain the SFA (years) or SFA (years, WWT) notations, SFA methods must be applied t

16、o the entire vessel. For vessels complying with Part 5A and 5B “Common Structural Rules for Bulk Carriers and Oil Tankers” of the Steel Vessel Rules, the design fatigue life for Spectral-based Fatigue Analysis is equal to 25 years or greater in 5-year increments. 3 Background (1 October 2017) (Revis

17、e Subsection 1/3, as follows. In the application of Part 5C of the Steel Vessel Rules, the SafeHull Fatigue Assessment technique is typically used to evaluate fatigue strength. The SafeHull Fatigue Assessment technique is a permissible stress range approach that is readily applied to large portions

18、of a vessels hull structure. The technique is required for certain vessels such as an oil tanker with a Rule length greater than 150 m for which the technique is detailed in Appendix 5C-1-A1 of the Steel Vessel Rules. The technique was derived considering unrestricted ocean service wave loads repres

19、enting the North Atlantic and a design fatigue life of 20 years. Part 5A and 5B “Common Structural Rules for Bulk Carriers and Oil Tankers” of the Steel Vessel Rules requires a design fatigue life of 25 years with wave loads representing the North Atlantic and multiple fatigue assessment techniques

20、are employed. A simplified stress analysis method based on beam theory is presented in Part 5A, Pt 1, Ch 9, Sec 4 of the Steel Vessel Rules, a finite element stress analysis approach is described in Part 5A, Pt 1, Ch 9, Sec 5 of the Steel Vessel Rules and structural design following the detailed des

21、ign standards is discussed in Part 5A, Pt 1, Ch 9, Sec 6 of the Steel Vessel Rules. Supplementary to the SafeHull Fatigue Assessment technique or methods employed for vessels complying with Part 5C of the Steel Vessel Rules, ABS may require the use of additional or alternative techniques to demonstr

22、ate the fatigue strength adequacy of structural components. These techniques may include Spectral-based Fatigue Analysis methods. In many instances the structural details cannot be adequately analyzed via the permissible stress range fatigue assessment approach. An optional classification notation,

23、FL (years), may be requested in cases in which the owner or designer increases the target fatigue lives of some or all of the structural components above the 20 year minimum value. This notation is discussed in the Steel Vessel Rules and does not require the use of SFA methods. 2 ABSGUIDE FOR SPECTR

24、AL-BASED FATIGUE ANALYSIS FOR VESSELS .2016 Notice No. 2 October 2017 SECTION 2 SPECTRAL-BASED FATIGUE ANALYSIS PROCEDURE OVERVIEW 1 General 1.7 Fatigue Strength Assessment (Section 6) (Correct numbering and revise Subparagraph 2/1.7.3, as follows.) 1.7.3 Acceptance Criteria (Subsection 6/9) (1 Octo

25、ber 2017) To meet the requirements of the SFA (years) or SFA (years, WWT) notations, the calculated fatigue life is to be equal to or greater than the design fatigue life. SECTION 4 STRUCTURAL ANALYSIS 1 General (1 October 2017) (Revise fifth paragraph of Subsection 4/1, as follows. Remainder of tex

26、t and Figure 1 are unchanged.) The effect of sloshing loads due to fluid in partially filled tanks is not within the scope of the SFA (years) or SFA (years, WWT) classification notations. However, the designer is encouraged to perform and submit such calculations, if deemed important. SECTION 5 SPEC

27、TRAL ANALYSIS 3 Wave Spectra and Wave Scatter Diagram (1 October 2017) (Revise last paragraph of Subsection 5/3, as follows. Remainder of text is unchanged.) Section 5, Tables 1 and 2 present the wave scatter diagram data that is to be used in the spectral-based fatigue analysis of a vessel classed

28、for unrestricted service and for world-wide trading service, respectively. It can be assumed that there is an equal probability of each vessel heading relative to the direction of the waves. (Revise title of Section 5, Table 1, as follows. Table is unchanged.) TABLE 1 ABS Wave Scatter Diagram for Un

29、restricted Service Classification (Representing the North Atlantic) ABSGUIDE FOR SPECTRAL-BASED FATIGUE ANALYSIS FOR VESSELS .2016 3 Notice No. 2 October 2017 (Add new Section 5, Table 2, as follows.) TABLE 2 ABS Wave Scatter Diagram for World-Wide Trading Service Classification (1 October 2017) * W

30、ave heights taken as significant values, Hs* Wave periods taken as zero crossing values, TzWave Period (sec)* Sum Over All Periods 3.50 4.50 5.50 6.50 7.50 8.50 9.50 10.50 11.50 12.50 13.50 WaveHeight(m)*0.5 1888 5417 5836 3392 1260 313 55 8 1 18170 1.5 493 3739 8374 9339 6517 2985 940 219 41 6 1 32

31、654 2.5 96 1128 3682 5934 6159 4216 1930 629 158 33 6 23971 3.5 18 294 1217 2439 3269 2959 1769 734 229 57 12 12997 4.5 4 79 388 893 1417 1568 1142 568 208 60 15 6342 5.5 1 23 130 328 581 745 631 361 150 49 13 3012 6.5 8 47 126 239 341 325 208 96 34 10 1434 7.5 2 18 51 101 156 163 115 58 22 7 693 8.

32、5 1 7 21 44 72 82 63 34 14 5 343 9.5 3 10 20 34 42 34 20 9 3 175 10.5 1 5 10 17 22 19 11 5 2 92 11.5 1 2 5 9 12 10 7 3 1 50 12.5 1 3 5 6 6 4 2 1 28 13.5 1 1 2 3 4 3 1 1 16 14.5 1 2 3 5 5 4 2 1 23 Sum over All Heights 2500 10691 19704 22543 19628 13425 7127 2983 1024 297 78 100000 SECTION 6 FATIGUE S

33、TRENGTH ASSESSMENT (Revise Subsection 6/9, as follows.) 9 Acceptance Criteria (1 October 2017) The minimum required fatigue life for a spectral-based approach is customarily stated as either a damage ratio (D) or a design fatigue life (L). The latter is employed in this Guide. To meet the requiremen

34、ts of the SFA (years) or SFA (years, WWT) notations, the calculated fatigue life is to be equal to or greater than the design fatigue life. 4 ABSGUIDE FOR SPECTRAL-BASED FATIGUE ANALYSIS FOR VESSELS .2016 Notice No. 2 October 2017 APPENDIX 2 FATIGUE STRENGTH ASSESSMENT (Revise Note (1), as follows.

35、Note (2) remains unchanged.) Notes: (1) (1 October 2017) This Appendix is referred to in Section 6. It is provided to describe the formulations comprising a Spectral-based Fatigue Analysis approach, which can be employed to satisfy the criteria to obtain the SFA (years) or SFA (years, WWT) Classific

36、ation notations. However, it is at this formulation level that there are multiple valid methods that may be selected. For that reason, it is emphasized that the contents of this Appendix are provided primarily to illustrate principle rather than to give mandatory steps for the Spectral-based Fatigue method. ABSGUIDE FOR SPECTRAL-BASED FATIGUE ANALYSIS FOR VESSELS .2016 5