Utilisation of principles from structural reliability in quantitative risk analysis: example from an offshore transport problem

The objective of this paper is to discuss the use of methods developed for calculation of the reliability of structures as a general tool for calculating probabilities within the context of quantitative risk analysis. By applying these methods the analyst is enabled to model the system, the uncertainties and the parameter correlations separately and systematically. This is ensured by flexible event and system modelling by logical combination of limit state functions and suitable uncertainty modelling by assigning marginal probability distributions and correlation measures. These properties might enable the analyst to include more knowledge in the analysis, compared to models traditionally applied in quantitative risk analysis. The subjectivistic theory of probability, which consistently allows subjective considerations to be included in the analysis, is adopted and provides the framework for the discussions. The paper concludes that methods of structural reliability represent a useful tool for calculating probabilities in a great number of situations in quantitative risk analysis. An example from an offshore towing operation sketches how these methods can open for stochastic modelling more in line with the characteristics of the actual system, compared to a typical event tree approach.