Consequence of Whipping and Springing on Fatigue and Extreme Loading for a 13000TEU Container Vessel Based on Model Tests

摘要

DNV, BV, HHI, CeSOS and Marintek have joined forces to investigate further the effect of springing and whipping on a 360m ultra large twin island container ship design. Model tests with a new flexible design have been carried out to investigate how the wave induced vibration affects the fatigue and extreme loading at different cross sections. The focus is given to the consequence of extreme loading with whipping based on long duration tests in realistic extreme weather, but also the effect of whipping (and springing) on fatigue is 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 results confirm that wave induced vibrations dominate the fatigue damage (65% of the total) for the East Asia to Europe trade in head seas. When a vessel is intended for operation in harsh ocean, where fatigue is an issue, it is recommended to include the effect of wave induced vibration in the design phase. Further, even though the vessel vibrates basically all the time, whipping is considered far more important than springing. The whipping magnitude can be quite dramatic in higher sea states, and superimposed on the wave frequency loading, the total bending moment may reach uncomfortable high levels (up to 1.8 times IACS rule loads). Hence, prudent seamanship is considered wise when encountering higher storms in head seas due to effect of whipping.