Influence of Sea State Models on Calculated Naval Vessel Stress Spectra


  1. Thompson, I.M.
Corporate Authors
Defence Research and Development Canada, Atlantic Research Centre, Halifax NS (CAN)
Fatigue damage is a governing factor in a naval ship’s design life, can limit the vessel’s operational capability and availability, and can significantly affect through-life maintenance costs. The development of reliable tools to assess a naval ship’s fatigue life will enable better management of aging fleets and facilitate the design of more resilient hulls. Spectral fatigue analysis of ships involves applying hydrodynamic wave loads to a structural finite element model. The resulting stress response amplitude operators are combined with wave data to calculate stress spectra which are used with S-N curves to estimate the fatigue crack initiation life. In this paper, data from a naval vessel sea trial are used to validate STRUC_R, spectral fatigue analysis software developed by Cooperative Research Ships (CRS). The calculated stress spectra are compared with measurements at fifteen structural locations and found to be in reasonable agreement with several exceptions. The effect of using long-crested and two-dimensional seaway models of measured conditions are compared. Results closer to measurements are obtained with two-dimensional models, but long-crested results provide a reasonable approximation. As most available wave data are one-dimensional, this provides a better understanding of the uncertainty long-crested wave assumptions introduce in naval vessel stress spectra calculations.
STRUC_R;spectral fatigue analysis;wave model
Report Number
DRDC-RDDC-2015-P148 — External Literature
Date of publication
12 Jan 2016
Number of Pages
Electronic Document(PDF)

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