Prediction of Extreme and Fatigue Sea Loads Using Linear Theory
DEFENCE RESEARCH ESTABLISHMENT ATLANTICDARTMOUTH (NOVA SCOTIA)
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This report presents three different approaches for determining exceedence probabilities of ship sea loads using linear strip theory. The first two approaches use nominal maximum loads for hourly and variable duration seaways, while a third approach considers individual load cycle amplitudes in all seaways. Of the three approaches, the load cycle approach appears to be most useful and can be used for both fatigue and ultimate load computations. Sample computations for the Canadian Patrol Frigate demonstrate the application of the methods. Gumbel distributions provide good fits to computed lifetime load exceedence probabilities. For load cycle and nominal hourly maximum loads, Weibull distributions provide superior fits. Future work should include three-dimensional hydrodynamic forces, nonlinear load effects, and the influence of wave conditions on ship speed and heading.
- Marine Engineering