海洋構造物の横振動に関する研究 (第2報)

抄録

In order to make a simplified analysis on the lateral vibration of the off-shore structure constructed with four legs and a platform, the same method as one used in the first report was again applied in this analysis by replacing the structure with two-dimensional portal frame, evaluating its flexual rigidity and then by transforming the structure into the equivalent lumped-mass model. Furthermore, the validity of this method was examined by the model experiments carried out on two kinds of the 4 leg-structures.
The main results obtained are as follows:
(1) The natural frequency obtained by the simplified method which utilizes Theory (2) or Theory (4) proposedin this study, coincides with the experimental frequency within the error range that is about 0.06-5.47%.
(2) As the ratio of the distance between legs and their span-lengths is smaller, the error of the natural frequency calculated by the above-mentioned method is more reduced and so its precision of calculation becomes higher. Therefore, the proposed method would be useful enough to analyse the natural frequency of the lateral vibration of the general offshore structure which has the small value of the above-mentioned ratio.
(3) Furthermore, this method gives the fairly well estimated value with respect to the amplitude of lateral vibration of the structure, since the error involved in the estimation is only about 9-13% at the fifth period of vibration.