Study on Fatigue Strength Evaluation of Ship Structural Members in The Ocean Going

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In order to develop a more reliable and accurate fatigue design method for ship structural members, a new type of fatigue design chart is proposed. These charts are derived by the following three procedures : (1) use of fatigue crack growth analysis as the basis for fatigue strength evaluation, (2) implementation of the authors' new storm model for the time history of stress occurrence induced by wave load and (3) incorporation of a new sailing model instead of the all headings model. The charts are 3-dimensional and are composed of the following three parameters : 1) maximum stress amplitude in the external load, 2) stress concentration factor and 3) fatigue crack length in cracked structural members. They can be prepared for any fatigue life and be used for initial fatigue design instead of the current fatigue design code. They also predict the residual fatigue life in cracked structural members when fatigue cracks are found after a certain service period.