Fatigue Assessment by Feeding Back the Results of Stress Measurements

The stress measurements of a ship and the spectrum-based fatigue assessment using AIS and Hindcast data were carried out. Then, practical improvement of fatigue assessment accuracy was examined. The relationship of the RMS (root mean square) values of random stress fluctuations in the short-term sea between analysis and measurements was examined. Also, the coefficient, which defines the equivalent stress range for calculating short-term fatigue damage according to Rayleigh distribution, was investigated. They vary stochastically but converge to a specific value after a particular measurement period. Their stochastic characteristics affect Short-term fatigue damage, but long-term cumulative fatigue damage is not affected. Using the converged values as representative values, it is possible to accurately predict long-term fatigue damage by accumulating short-term fatigue damage by Rayleigh distribution characterized by analytical rms values.