Consequence of Whipping and Springing on Fatigue for a 8600TEU Container Vessel in Different Trades Based on Model Tests

摘要

DNV, HHI, CeSOS and Marintek have joined forces to investigate further the effect of springing and whipping on a real 340m container vessel. Model tests with a new flexible design have been carried out to investigate how the wave induced vibration affects the fatigue loading at different cross sections. The focus is given to the consequence of wave induced vibrations on fatigue in various trades. However, the effect of whipping on extreme loading is also briefly investigated. The tests are carried out in head seas, and all parameters are realistic such as loading condition, vibration shape, vibration frequencies, damping, wave spectra and speed. The model setup is however arranged for subsequent torsion vibrations assessment for other wave headings. The results confirm that wave induced vibrations can be of considerable magnitude relative to the conventional wave damage for the different trades. When a vessel is intended for operation in harsh ocean, where fatigue in general is an issue, it is recommended to include the effect of wave induced vibration in the design phase. The maximum whipping response is also relatively high, considered typical for this vessel type and size. With whipping the IACS rule levels may easily be exceeded also in less harsh storms. Hence, prudent seamanship is considered wise when encountering severe storms in head seas due to the effect of whipping. The vibration, as an indicator, will be easily felt onboard, but hull monitoring is regarded as a better alternative to capture both the effect of vibration on fatigue and extreme loading.