In the ship structure the main vibratory sources are a main engine and a propeller, as well known. As these sources are directly and firmly connected to the ship structure, coupled vibrations have been recently clarified by the simultaneous observations. The analytical and experimental researches on the coupled vibraticns of the main engine, the propulsive shaft system and the ship structure including its local structure are presented.
The analysis and estimation method of the natural frequencies of the engine room of ship as space frame work, and the good agreement of the estimated frequencies and the observed ones, have been described.
The experimental studies, such as the coupled vibrations of a diesel engine model and the large ship model, them of the actual ships and them of a turbine and the double bottom as local structure of ship, have been described.
The other coupled vibrations of the longitudinal vibrations of the shaft system and the superstructure in some actual ships have been presented.

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