AN APPLICATION OF BUILDING BLOCK METHOD TO VIBRATION PROBLEM OF DIESEL POWERED SHIP

An application of the building block method to the vibration analysis of ship structures is described. The structure is divided into several component structures, and after the vibratory characteristics of the component structures are obtained, they are joined together to form the composite structures. The authors have developed a simple method to apply to the design calculation of ship vibration problems. It is shown how the method is derived using a theory of modal synthesis, and to confirm the validity of the theory, experiments were carried out with a seven-meter-long aluminum model ship. The calculation is then made for the coupled vibration of the main hull, the superstructure and the propulsion shaft of the diesel-powered ship. The calculated results qualitatively agree with data from the authors' experience with full-scale ships. Finally, the authors examine the relation between the response of the superstructure and the ratio of natural frequency of superstructure to that of the crankshaft.