Fatigue Damage Assessment Based On Full Scale Measurement Data For a Large Container Carrier

As modern container vessels become larger and more flexible, the uncertainty of the fatigue assessment has been increased. In the convectional ship rules, the fatigue damage is evaluated based on the linear wave load. For the larger container carriers, however, the wave induced vibration, so called whipping and/or springing, has to be considered, due to their flexible bodies. In this paper, the fatigue damage due to whipping and/or springing has been evaluated with the full scale measurement data. The measured vessel is an 8000TEU container vessel. The full scale measurement for the vessel started from 2006 with joint project of SHI, ABS and OOCL. Rainflow counting method and the Palmgren-Miner rule are used to evaluate fatigue damage. At first, the total fatigue damage has been evaluated with raw data and then the fatigue damage from wave component has been evaluated with low pass filtered data. The effect of springing and/or whipping on the fatigue damage is obtained from the difference with the total fatigue damage and the fatigue damage from wave component. From the results, the effect of springing and/or whipping on the fatigue damage is about 30% of the total fatigue damage. The total fatigue damage, however, is much less than the design fatigue damage. Since the main operation route is from Far East to Europe. The weather condition of this region is known to be much milder than North Atlantic which is generally used for ship design. Nevertheless, the effect of springing and/or whipping on the fatigue damage cannot be neglected for the safe ship design.