The Influence of Different Scenarios of Supply Ship Collision on the Dynamic Response of a North-Sea Jacket-Pile-Soil System

In the present study, the influence of various scenarios of supply ship collisions, namely, bow, stern, and also broad-side impacts on a jacket-pile-soil system, is investigated. In the previous study of ship impact on an eight-leg North-Sea jacket platform by Amdahl and other authors, the effect of jacket-pile-soil interaction was not considered. The collision points on the jacket structure are also taken as joints and midspan of leg, horizontal and vertical braces, namely, hard and soft impact points. The speed and the weight of the colliding vessel are also varied for typical supply vessels. Several supply ship collision analyses are carried out for bow, stern and broad-side impact scenarios on an eight-leg North-Sea jacket platform. It is observed that by taking into account the jacket-pile-soil interaction effects, particularly in softer clayey soils, the amplitude of displacement response after the supply ship impact at the deck level is increased due to yield in the upper soil layers. Contrary to this finding, less linear dynamic effects can be seen in the studied jacket-pile-soil system subjected to the supply ship impact. It can also be concluded that for a soft impact scenario, the dynamic effects in the global response of the platform located in the mainly over-consolidated (OC) clayey soil may be much less than those for a hard impact scenario on the same platform. For instance, for a brace impact at its midspan, a less significant dynamic effect has been observed than for a leg impact. The duration of impact in such cases is shown to play an important role in determining the dynamic influence of the platform response. The relative energy absorption of the platform is shown to be more for broad-side loading. It is shown that the global response of the jacket platform during the collision with a supply vessel might depend largely on the scenario of the impact and, to some extent, on the pile-soil behavior. It is found that for the bow and stern impact scenarios, the energy contribution of the local member dent or buckling might be more significant than that for the broad-side loading for which the global frame energy contribution and the overall inertia effect of the platform might be a dominant factor.