Abstract
The theoretical analysis of the behaviour of the transverse section of the ship with many decks in the free vibration state has been made. The effect of the many decks, seen in the passenger ships, the engine rooms of the cargo ships, and others, to the eigenvalues and modes of the main structure, which is constructed with the members of the lowest deck, both side frames and the bottom, has been studied analytically and numerically. The generalized analysis was made in the condition that the transverse section with many decks was divided into the two elementary systems, that is, the main structure system explained above and named by the first system, and the other systems constructed with decks and both side frames connected to the main structure and named by the second system in Fig. 2. These analyses and results proposed here may be applied to the other structure than ship, which can be divided into the two elementary systems, in the same way. The eigenvalues and the eigenfunctions of these structure can be calculated from eqs. (12), (15), (16) and (18) for the symmetrical vibration, and eqs. (21), (24), (25) and (27) for the asymmetrical one. Numerically computed examples of the practical ship transverse section, which have two decks, are shown in Figs. 5 and 6, and also compared with the section of single deck. Another examples of the section with three decks constructed with the members of same scantling are shown in Figs. 7 and 8.
