Clasification Society Rulefinder 2020 - Version 9.33 - Fix
Common Structural Rules - Common Structural Rules for Bulk Carriers and Oil Tankers, January 2019 - Part 1 General Hull Requirements - Chapter 9 Fatigue - Section 1 General Considerations - 3 Assumptions

3 Assumptions

3.1 General

3.1.1 The following assumptions are made in the fatigue assessment:
  • a) A linear cumulative damage model, i.e. Palmgren-Miner’s Rule, given in Ch 9, Sec 3, [5], has been used in connection with the design S-N curves, given in Ch 9, Sec 3, [4].
  • b) Design fatigue life, TDF, is taken not less than 25 years.
  • c) Rule quasi-static wave induced loads are based on North Atlantic wave environment. They are determined at 10-2 probability level of exceedance by the Equivalent Design Wave (EDW) concept.
  • d) Net thickness tn50 approach is used, according to [5].
  • e) Type of stress used for crack initiating at the weld toe is the hot spot stress. Type of stress used for crack initiating at free edge of non-welded details is local stress at free edge.
  • f) Fatigue stress range ΔσFS may be calculated by simplified stress analysis or by finite element stress analysis for details with more complex geometry.
  • g) Long term distribution of stress range of a structural detail is assumed to follow a two-parameter Weibull distribution. Weibull shape parameter ξ is equal to 1 and the fatigue stress range ΔσFS is given at the reference probability level of exceedance equal to 10-2.
  • h) The acceptance criteria for fatigue checking are the total fatigue damage D to be less than 1 for the design fatigue life, as required in Ch 9, Sec 3, [2].
Parent topic: Section 1 General Considerations
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