Numerical investigation of wave-induced vibrations and their effect on the fatigue damage of container ships

Wave-induced vibrations of the ship hull girder consist of springing when it is associated with a resonance phenomenon, and whipping when it is caused by a transient impact loading due to wave slamming. This paper presents a new approach to predict the wave-induced vibrations and their contributions to fatigue damage of container ships. The seakeeping, whipping, springing and elastic modes calculations are coupled in every time step. According to the design characteristics of large container ships the existing methods are modified, air cushion effect and flow separation are considered in the slamming calculation, symmetric and asymmetric vibration modes equations are applied to predict the springing response in head seas and oblique seas. Based on rain flow counting method, spectral-based analysis method is used to calculate the additional fatigue damage due to springing and whipping.