Linking fault tree analysis to probabilistic damage stability calculation

Traditional damage stability assements focus on ship stability after damage has occurred. Certain regulations may also require redundancies, such as Safe Return to Port. To date, a comprehensive assessment of damage stability has been decoupled from other redundancy requirements in regulatory terms, possibly allowing initially non-critical damages to cause an impermissible deterioration of the system despite the redundancy measures. Linking probabilistic damage stability calculation with damage-based functional chain evaluation would enable a more comprehensive assessment of ship safety, particularly in the passenger ship sector and in the field of naval vessels. This paper shows how a probabilistic damage stability calculation based on the Monte Carlo principle is extended with a fault tree analysis for functional chain evaluation, using an in-house developed code. Particular attention is paid to the modelling and information allocation to the basic events, as well as their evaluation and integration into the existing safety index. By linking basic fault tree events with compartments, a connection is established between damage cases and possible failures of the functional chain. The results show, using a modelled example, that integrating functional chain evaluation into probabilistic damage stability calculation can lead to a significantly lower attained index, indicating potential failure of critical ship functions post-damage and highlighting the importance of ship layout beyond initial damage. Concepts traditionally used in naval shipbuilding, such as section self-sufficiency, may also be relevant for passenger ships in a less pronounced form. The current modeling of ship safety using a required subdivision index already provides a basic assessment. Traditional approaches to requiring a certain level of resilience, such as Safe Return to Port regulations, are not sufficient to demonstrate this beyond doubt because of their deterministic nature, demanding essentially a one compartment status for functions. Therefore, the required subdivision index for certain ship types should also include an assessment of the vulnerabilities of critical functional chains.

Content

Subjects

damage stability

fault tree analysis

functional chain

ship safety

ship design

vulnerability

DDC Class

600: Technology