Ship vibrates locally and globally from various sources of excitation. While most literature focus on propeller and engine excited vibrations, which can be handled by proper design, wave induced vibration can not easily be avoided by moderate changes of the hull lines. The waves may cause the whole hull girder to vibrate due to springing (resonance) and whipping (transient response), which increase the fatigue and extreme loading. DNV has done extensive research on this topic the last decade, and recently, it has also become an industry concern. Commercial modern hull monitoring systems (such as HMON systems that satisfy class requirements) in combination with sophisticated model tests are the best tools to answer the key questions: How important is the wave induced vibrations, and does it have to be included in design rules? Full scale measurements have been carried out for two different container vessels operating in the North Atlantic. Model tests have also been carried out for the larger vessel. This paper focus on the additional contribution to fatigue damage from wave induced vibration. Results are obtained both amidships and in front of the superstructure. The extensive measurements illustrate that the wave induced vibrations are significant, and furthermore, the general fatigue loading can be high for this trade. For some details, the loading including vibration can also be higher than considered in design rules. This is also confirmed by observed fatigue cracks after relatively short time of operation. State-of-the-art design procedures have to be used to avoid such cracks in this harsh trade, but measurement systems can also be used to decrease the fatigue loading by awareness and routing.
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