A Study on Higher Mode Vibration of Ships (1st report)

A method for the calculation of the coupled vibration has been derived using the concept of modal synthesis. The modal parameters such as frequency, modal mass and modal damping and the vibration mode of the coupled vibration can be calculated by the present method using the modal parameters, vibration mode and mass distribution of uncoupled vibration. The applicability of the method is studied to the higher mode vibration of ship structure which is the complicated coupled vibration of the substructures and the main hull girder. The isolated calculation of individual local structure, such as superstructure, double bottom in engine room etc can be combined to yield the final results coupled with main hull vibration. By the present method, it is easy to distinguish what is the main part of coupled vibration. This is very useful from the point of view of the structural design. The calculation and the experiment should be compared in order to confirm the validity of the method in the future works.