On the Lateral Vibration of a Boring-rod in the Deep Sea

抄録

The lateral vibration and bending stress of a boring-rod induced by drifting and rolling motions of a drilling vessel floating on the deep sea were analyzed theoretically.The results of this study predict when and where the maximum displacement and bending stress occur along the rod, depending on a given damping factor of the surrounding water.When the non-dimensional damping factor, N, defined in this paper, is less than about 1.0, resonant vibrations of the rod are caused bya the vessel-motions, whereas they disappear when N exceeds the above value.Inthis case, however, the maximum bending stress increases with an increasing fequency of vibration of the rod.Finally, the analysis, applied to practical cases, has revealed that the present rule of thumb for the safety operation of an off-shore boring is not applicable to all cases encountered in ocean engineering.