1、 ABSGUIDANCE NOTES ON SPECTRAL-BASED FATIGUE ANALYSIS FOR VESSELS .2004 1 GUIDANCE NOTES ON SPECTRAL-BASED FATIGUE ANALYSIS FOR VESSELS (FOR THE SFA (years) CLASSIFICATION NOTATION) JANUARY 2004 NOTICE NO. 4 January 2012 The following Changes become EFFECTIVE AS OF 1 FEBRUARY 2012. (See http:/www.ea
2、gle.org for the consolidated version of the Guidance Notes on Spectral-based Fatigue Analysis for Vessels 2004, 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 constr
3、uction, unless otherwise noted. SECTION 2 ESTABLISHING FATIGUE DEMAND (Revise Subsection 2/7, as follows.) 7 Combined Fatigue from Multiple Base Vessel Loading Conditions (1 February 2012) Because of the variability in Base Vessel Loading Conditions and its effects on the fatigue strength prediction
4、s, it is necessary to consider more than one base case in the fatigue analysis. As a minimum, two cases should be modeled and used in the Spectral-based Fatigue Analysis process. The two cases are ones resulting from, and representing, the probable deepest and shallowest drafts, respectively, that t
5、he vessel is expected to experience during its service life. A factor of 0.85 is to be applied to account for non-sailing time for operations such as loading and unloading, repairs, etc. for conventional trading vessels. For vessels engaged in a service with less sailing time, special consideration
6、may be given to accepting a lower factor, subject to Owner agreement. Note: Suggested Approach: In some (so-called “Closed Form”) formulations to calculate fatigue demand, the fraction of the total time for each Base Vessel Loading Condition is used directly. In this case, potentially useful informa
7、tion about the separate fatigue damage from each vessel loading condition is not obtained. Therefore, it is suggested that the fatigue damage from each vessel loading condition be calculated separately. The combined fatigue life is then calculated as a weighted average of the reciprocals of the live
8、s resulting from considering each case separately. For example, if two base loading conditions are employed, and the calculated fatigue life for a structural location due to the respective base vessel loading conditions are denoted L1and L2, and it is assumed that each case is experienced for one-ha
9、lf of the sailing time during the vessels service life, then the combined fatigue life, LC, is: LC = 1/0.850.5(1/L1)+ 0.5(1/L2). As a further example, if there were three base vessel loading conditions L1, L2, and L3with exposure time factors of 40, 40, and 20 percent, respectively; then the combined fatigue life, LC, is: LC = 1/0.850.4(1/ L1) + 0.4(1/ L2) + 0.2(1/L3).
