Vibrations of Superyacht Structures: Comfort Rules and Predictive Calculations

The dynamic behaviour of hull structures has a great impact on the comfort level on board modern superyachts and, from the structural point of view, this is one of the subjects shipyards are more interested in. In addition many important Classification Societies have issued new rules and regulations for the evaluation of vibration maximum levels. Such rules, usually named as "Comfort Class Rules", contain both the general criteria for noise and vibration measurement in various yacht areas, and maximum limit values which such measurements should fall into. Despite the effort of Classification Societies to keep a certain harmonization of criteria and of limit values, the existing diversities often create serious uncertainties to designers. In this work a case study is presented, consisting in a 60 meters superyacht, on which a detailed FEM investigation has been carried out in order to investigate the dynamic behaviour of hull and superstructures. The results of modal and transient analyses are compared with a first series of experimental data gathered during the vessel construction. At the moment sea trial are under course and the vibration measurements are going to be carried out in several part of the vessel.