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 3 Fatigue Evaluation - 1 Fatigue Analysis Methodology

1 Fatigue Analysis Methodology

1.1 Cumulative damage

1.1.1 The fatigue assessment of the structure is based on the application of the Palmgren-Miner cumulative damage D taken as:

where:

ni : Number of cycles at stress range Δσi.

Ni : Number of cycles to failure at stress range Δσi.

ntot : Total number of stress range blocks.

i : Stress range block index.

1.1.2 As the long term stress range distribution of a structural detail in a ship can be described by a two-parameter Weibull distribution, as given in Ch 9, Sec 1, [3.1.1], fatigue damage can be obtained by means of a closedform equation, as given in [5].

1.2 Fatigue strength assessment

1.2.1 Assessment of the fatigue strength of structural members according to [2] includes the following three steps:
  • a) Calculation of stress ranges, according to [3].
  • b) Selection of the design S-N curve, according to [4].
  • c) Calculation of the cumulative damage and the fatigue life calculation, according to [5].
Parent topic: Section 3 Fatigue Evaluation
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