Estimation of Natural Frequency of Superstructure for Fore-and-aft Vibration using Database

Abstract

This paper presents an estimation method of natural frequency of superstructure. Accuracy of several exsisting empirical formula were examined by using newly developed database system of superstructure vibration. In order to obtain an accurate simple formula, some empirical formula having different parameters were derived from regression analysis by database. It is found that height of vibration layer introduced by Hirowatari's method gives the best accuracy as a parameter of empirical formula. However, accuracy of simple formula can not be expected that within 12% because these formula does not take into account complexity and variety of superstructure and coupled effect of ship hull vibration.