Modeling Dynamic Ground Reaction to Predict Motion of and Loads on Stranded Ships in Waves

Abstract

Ship groundings are a low probability event, but can create severe environmental and financial consequences. The objective of this thesis is to provide knowledge and understanding of the grounded ship condition to salvors and ship owners so they can reduce the possible negative consequences of future ship groundings. There has been very little research on the motions of and loads on a grounded ship in waves. In this thesis, a model of the ground reaction forces due to the steady state motions of a grounded ship is developed. This model is derived from civil engineering applications but tailored to the stranded ship problem. The ground reaction sub-model is part of a ship motion model that predicts grounded ship motions and loads in waves. The model input specifies the static grounded equilibrium condition and static grounded forces. The model calculates steady state motions and loads around the equilibrium condition. This thesis describes a preliminary version of the full six degree of freedom model in which soil reactions are accounted for in two degrees of freedom, heave and pitch, assuming a rectangular shaped hull. Bottom types are categorized as sand, mud, coral and rock. The ship can be embedded or resting on the surface of the bottom.