A Study on Risk Assessment for Anchor Dragging Using On-board Measurement Data of a Single Anchored Vessel

Abstract

A new risk assessment method for anchor dragging is proposed. Using several kinds of information that can be commonly obtained on the navigational bridge of ships, the touch down point of the anchor chain to the seabed is estimated based on the ship’s equations of motion. Firstly, accelerations and velocities of the ship are numerically evaluated using GPS data. Secondly, the hydrodynamic forces, such as added mass, damping force and wind force, are estimated based on the theory of ship maneuverability. Thirdly, the tension of the anchor chain is determined as a residual term of the equations of motion. Finally, the touch down point of the anchor chain to the seabed is estimated based on the catenary theory. In this study, the point is named as the Virtual Touch Down Point (VTDP) and used for estimation of the length of the anchor chain crawling on the seabed and its holding power.