波浪によるロッドの横振動の解析
海洋ボーリングロッドの振動について (第3報)
1973 年 89 巻 1024 号 p. 363-368
詳細
1973 年 89 巻 1024 号 p. 363-368
The forced vibration of an off-shore boring rod caused by wave was analysed under the assumptions of a linear damping of the surrounding water and of a deep water wave with finite amplitude for a disturbing force.
The results obtained by this analysis were as follows:
1) The maximum amplitude of lateral vibration of rod caused by the wave occurred in different positions according to the vibration modes.However, the maximum bending stress produced on rod always occurred either on the surface of the sea or at the bottom of the sea.
2) The condition of resonance appeared when the quantity, kcu/ωn, approached to the value little less than 0.5, wherek, cωandωnwere wave number, wave velocity and circular natural frequency at nth order respectively.In the narrow range of this quantity including the resonance point, both the amplitude and bending stress of rod abruptly increased their magnitude.
3) Within the range in question, the amplitude of vibration of rod in resonance decreased and the corresponding bending stress increased in higher modes of vibrations.In addition, the amplitude as well as the bending stress in resonance was exponentially decreased as the increase of damping effect of the surrounding water.
4) The amplitude and the stress in resonance increased with the increase of value of the weight parameterW, and decreased with the increases of the'weight ratioKandl/L, these quantities of which were defined by the author.
