1、 ABSGUIDANCE NOTES ON SPECTRAL-BASED FATIGUE ANALYSIS FOR VESSELS .2004 1 GUIDANCE NOTES ON SPECTRAL-BASED FATIGUE ANALYSIS FOR VESSELS (FOR THE SFA OF SFA (years) CLASSIFICATION NOTATION) JANUARY 2004 NOTICE NO. 2 December 2007 The following Changes become EFFECTIVE AS OF 1 DECEMBER 2007. (See http
2、:/www.eagle.org/rules/downloads.html for the consolidated version of the Guidance Notes on Spectral-based Fatigue Analysis for Vessels 2004, updated in August 2006, with all Notices and Corrigenda incorporated.) Notes - The date in the parentheses means the date that the Rule becomes effective for n
3、ew construction based on the contract date for construction, unless otherwise noted. SECTION 1 INTRODUCTION 1 Purpose and Applicability (1 December 2007) (Add new last paragraph to Subsection 2/1, as follows.) For vessels complying with Part 5A “Common Structural Rules for Double Hull Tankers” or Pa
4、rt 5B “Common Structural Rules for or Bulk Carriers” of the ABS Rules for Building and Classing Steel Vessels, the design target fatigue life for Spectral-based Fatigue Analysis is equal to 25 years. SECTION 2 ESTABLISHING FATIGUE DEMAND 3 Stress Range Transfer Function (1 December 2007) (Add new la
5、st paragraph to Subsection 2/3, as follows.) In the course of seakeeping analysis, 75% of vessels design speed is to be used for the prediction of motions and pressures. Notice No. 2 December 2007 2 ABSGUIDANCE NOTES ON SPECTRAL-BASED FATIGUE ANALYSIS FOR VESSELS .2004 SECTION 8 FATIGUE STRENGTH 3 S
6、-N Data (1 December 2007) (Revise third paragraph of Subsection 8/3 and add new fourth paragraph, as follows.) To provide a ready reference, the S-N Data recommended by ABS are given in Appendix 2 of this Guide. (Note: source United Kingdoms Dept of Energy (HSE) Guidance Notes, 4thEdition.) There ar
7、e various adjustments (reductions in capacity) that may be required to account for factors such as a lack of corrosion protection (coating) of structural steel and relatively large plate thickness. The imposition of these adjustments on fatigue capacity will be in accordance with ABS practice for ve
8、ssels. There are other adjustments that could be considered to increase fatigue capacity above that portrayed by the cited S-N data. These include adjustments for compressive “mean stress” effects, a high compressive portion of the acting variable stress range and the use of “weld improvement” techn
9、iques. The use of a weld improvement technique, such as weld toe grinding or peening to relieve ambient residual stress, can be effective in increasing fatigue life. However, credit should not be taken of such a weld improvement in the design phase of the structure. Consideration for granting credit
10、 for the use of weld improvement techniques should be reserved for situations arising during construction, operation or future reconditioning of the structure. An exception may be made if the target design fatigue life cannot be satisfied by other preferred design measures such as refining layout, g
11、eometry, scantlings and welding profile to minimize fatigue damage due to high stress concentrations. The calculated fatigue life is to be greater than 15 years excluding grinding effects. Where grinding is applied, full details of the grinding standard including the extent, profile smoothness parti
12、culars, final weld profile, and grinding workmanship and quality acceptance criteria are to be clearly shown on the applicable drawings and submitted for review together with supporting calculations indicating the proposed factor on the calculated fatigue life. Grinding is preferably to be carried o
13、ut by rotary burr and to extend below the plate surface in order to remove toe defects and the ground area is to have effective corrosion protection. The treatment is to produce a smooth concave profile at the weld toe with the depth of the depression penetrating into the plate surface to at least 0
14、.5 mm below the bottom of any visible undercut. The depth of groove produced is to be kept to a minimum, and, in general, kept to a maximum of 1 mm. In no circumstances is the grinding depth to exceed 2 mm or 7% of the plate gross thickness, whichever is smaller. Grinding has to extend to areas well
15、 outside the highest stress region. Provided these recommendations are followed, an improvement in fatigue life up to a maximum of 2 times may be granted. Notice No. 2 December 2007 ABSGUIDANCE NOTES ON SPECTRAL-BASED FATIGUE ANALYSIS FOR VESSELS .2004 3 APPENDIX 1 WAVE DATA (Replace Table 1 in its
16、entirety with following.) TABLE 1 ABS Wave Scatter Diagram for Unrestricted Service Classification (1 December 2007) * Wave heights taken as significant values, Hs* Wave periods taken as zero crossing values, TZWave Period (sec)* 3.50 4.50 5.50 6.50 7.50 8.50 9.50 10.50 11.50 12.50 13.50 Sum Over Al
17、l Periods 0.5 8 260 1344 2149 1349 413 76 10 1 5610 1.5 55 1223 5349 7569 4788 1698 397 69 9 1 21158 2.5 9 406 3245 7844 7977 4305 1458 351 65 10 25670 3.5 2 113 1332 4599 6488 4716 2092 642 149 28 20161 4.5 30 469 2101 3779 3439 1876 696 192 43 12625 5.5 8 156 858 1867 2030 1307 564 180 46 7016 6.5
18、 2 52 336 856 1077 795 390 140 40 3688 7.5 1 18 132 383 545 452 247 98 30 1906 8.5 6 53 172 272 250 150 65 22 990 9.5 2 22 78 136 137 90 42 15 522 10.5 1 9 37 70 76 53 26 10 282 11.5 4 18 36 42 32 17 7 156 12.5 2 9 19 24 19 11 4 88 13.5 1 4 10 14 12 7 3 51 Wave Height (m)* 14.5 1 5 13 19 19 13 7 77
19、Sum over All Heights 8 326 3127 12779 24880 26874 18442 8949 3335 1014 266 100000 Notice No. 2 December 2007 4 ABSGUIDANCE NOTES ON SPECTRAL-BASED FATIGUE ANALYSIS FOR VESSELS .2004 APPENDIX 2 BASIC DESIGN S-N CURVES (Add new Notes below Table 1, as follows.) TABLE 1 Parameters For Basic S-N Design
20、Curves (1 December 2007) N 107N 107Class A (For MPa units) m C (For MPa units) r B 1.013 10154 1.013 10176 C 4.227 10133.5 2.926 10165.5 D 1.519 10123 4.239 10155 E 1.035 10123 2.300 10155 F 6.315 10113 9.975 10145 F2 4.307 10113 5.278 10145 G 2.477 10113 2.138 10145 W 1.574 10113 1.016 10145 Refer
21、to Part 5C of the Steel Vessel Rules on the categorization of structural details into the indicated classes. Notes for Application of Classes: Class B: Parent material with automatic flame-cut edges ground to remove flame cutting drag line. Class C: Parent material with automatic flame-cut edges and
22、 full penetration butt welds ground flush in way of hatch corners in container carriers or similar deck areas in other vessel types. Class D: Full penetration butt welds in way of hatch corners in container carriers or similar deck areas in other vessel types. APPENDIX 3 OUTLINE OF A CLOSED FORM SPE
23、CTRAL-BASED FATIGUE ANALYSIS PROCEDURE 3 Key Steps in Closed Form Damage Calculation (Revise Items 4 and 5, as follows.) 4. (1 December 2007) Using the spectral moments, the Rayleigh probability density function (pdf) describing the short term stress-range distribution, the zero up-crossing frequenc
24、y of the stress response and the bandwidth parameter used in calculating Wirschings “rainflow correction” are calculated as follows: (Equations are unchanged) Notice No. 2 December 2007 ABSGUIDANCE NOTES ON SPECTRAL-BASED FATIGUE ANALYSIS FOR VESSELS .2004 5 5. (1 December 2007) Calculate cumulative
25、 fatigue damage based on Palmgren-Miners rule, which assumes that the cumulative fatigue damage (D) inflicted by a group of variable amplitude stress cycles is the sum of the damage inflicted by each stress range (di), independent of the sequence in which the stress cycles occur: =JiiiJiiNndD11(7) w
26、here ni= number of stress cycles of a particular stress range Ni= average number of loading cycles to failure under constant amplitude loading at that stress range according to the relevant S-N curve J = number of considered stress range intervals Failure is predicted to occur when the cumulative da
27、mage (D) over J exceeds a critical value equal to unity. The short term damage incurred in the i-th sea-state, assuming a S-N curve of the form N = AS-m, is given by: =00)( dsgpfskkkATDiiimhmsti.(8) where Di= damage incurred in the i-th sea-state kh= a factor for high tensile steel, applicable to pa
28、rent material only = 1.000 for mild steel or welded connections = 0.926 for H32 steel = 0.885 for H36 steel = 0.870 for H40 steel kt= a factor for thickness effect, which is not applicable to the longitudinal stiffeners which are of flat bars or bulb plates = nt22for t 22 mm = 1.0 for t s4/2 = 0.85
29、+ 0.3ms/s4for s4/2 ms s4/2 = 0.7 for ms0) and the constant A changes to C, the expression for damage, as given in equation 12, is as follows: D = ATm)22( (m/2 + 1) =Mimiiiiipfm10)(),( (14) where iis the endurance factor having its value between 0 and 1 and measuring the contribution of the lower bra
30、nch to the damage. It is defined as: ()+=00011dsgsdsgskkkCAdsgsimSimmmmsthSimiQQ .(15) If g(s) is a Rayleigh distribution, then iis: ( ) )12/(),12/(1)/1(),12/(102/0+=mvrkkkvvmimmsthmiii (16) Notice No. 2 December 2007 8 ABSGUIDANCE NOTES ON SPECTRAL-BASED FATIGUE ANALYSIS FOR VESSELS .2004 where vi= 222iQS0= incomplete gamma function and is =xaduuuxa010)exp(),( See steps 2-6 above, regarding the fatigue safety check.
