A probabilistic evaluation of tank ship damage in grounding events

Abstract

Recent international and domestic regulatory actions have resulted in significant changes to oil tanker designs and intensified attention on predicting tanker environmental performance following groundings or collisions. The current analytical method defined by the International Maritime Organization (IMO) applies probabilistic damage extents to proposed designs to determine expected oil outflows, which are compared to reference double hull vessels. The IMO method considers the effect of subdivision on oil outflow, but does not account for the ability of a specific structure to resist rupture and minimize cargo loss. Further, IMO damage extents are based on a limited set of tanker casualty data, and do not reflect current trends in materials or construction. This thesis proposes a probabilistic method for evaluating the crashworthiness of new tankers using a theoretical model for predicting grounding damage extents rather than historical data. The procedure proposes developing and calibrating a probabilistic grounding scenario, then applying the scenario in a Monte Carlo simulation to alternative tanker designs for evaluation of Pollution prevention effectiveness. The simulation uses the structural damage model DAMAGE to predict bottom damage extents following a grounding for a series of notional single hull, double hull and intermediate oil-tight deck tankers of comparable size designed for this research. The effect of structural enhancements such as increasing plate thickness, densely packing longitudinal stiffeners or the adding more transverse framing is examined by comparing the oil outflow characteristics of a family of modified double hull tankers. This research is done in conjunction with simultaneous research into a similar method for tanker collisions.