Dynamic Behaviour of a Double-Articulated Column in Waves

In this paper, the characteristics of dynamic behaviour of double-articulated columns in regular waves is investigated with special emphasis being laid on the effect of static restoring force of columns on the dynamic behaviour of the column itself as well as the behaviour of total system including a moored tanker. For the numerical analysis of the behaviour of articulated columns without a moored tanker, two different methods, that is to say, double-pendulum approach and constraint matrix method are simultaneously utilized, but for the analysis of total system including a moored tanker the latter method was applied. From comparison between the predicted behaviour and the result of experiments performed in a water basin, it was found that both analytical methods are of use for predicting the dynamic behaviour of articulated columns. Furthermore, it was concluded that as far as the present investigation is concerned, the difference in the static restoring force characteristics of the column does not bring about serious differences in the response characteristics of the present mooring system in regular waves. However, it must be kept in mind that the static restoring force of the column should be large enough to avoid an excessive submersion of the buoy caused by the wave drifting force acting on a moored tanker.