On the Vertical Vibration Characteristics of Ships with Erections : Experimental and Theoretical Investigations Using Model Ships of Box Section

Abstract

In this paper have been assembled a number of cases of vertical vibration experiments carried out by the authors on the acrylic resin model ships of box section with deck erections. To clarify the vertical vibration characteristics of ships with erections, numerical calculations are carried out in the following manner. Firstly, nine structural parameters are defined, which are used to distinguish the structural differences among the ships with erections. Secondly, three basic ships are selected. The word "basic ship" means an imaginary ship, of which each structural parameter has an average value of those of model ships mentioned above. Using the calculation method previously reported by the present authors and starting from the basic ship, a series of numerical calculations of natural frequencies of ships in question is carried out by changing each of their parameters independently of the others. Using the results of calculations, vertical vibration characteristics of ships in question are given in the form of graphical presentation. Based on the results of calculations, a simple and practical method of estimating natural frequencies of ships with erections is proposed. Applying this method to the above-mentioned model ships, good agreement is obtained between the calculated and observed frequencies.