A Probabilistic Model of Flooding Loads on Transverse Watertight Bulkheads in the Event of Hull Damage

Abstract

Watertight bulkheads (WTBs) are crucial to ship survivability in the event of hull damage. Current design standards for WTBs are empirical and prescriptive in nature. However, damage-causing events and damaged ship response exhibit significant variabilities and uncertainties. Hence, the design and assessment of WTBs should be performed in a probability-based format. This paper outlines, as an essential input to reliability analysis, the development of a physically based probabilistic model of transverse WTB loads. Poisson arrival is assumed for damage events, and the maximum life-time load effect envelope on the WTB in damaged condition is derived. The emphasis of this paper is on the probabilistic modeling of loads; hence, simple phenomenological expressions of load components are used to underline the cause and extent of randomness in WTB loads. A response surface type approach is suggested for determining ship-specific model parameters. A large RO/RO vessel with side shell breach below the waterline is used for illustrating the application of the proposed methodology; randomness is considered in ship hydrostatic properties, damage location, length of breach, occurrence and duration of damage events, the environment, curve fitting, and modeling errors. Probabilistic estimates of the maximum load components are obtained through Monte Carlo simulations. These are compared with available code-prescribed design values.