A Monte Carlo Based Model for Estimating the Reliability of Offshore Structures Exposed to Environmental Loading

Abstract In Denmark, as in many other countries, there is a legal requirement to ensure that risks related to health and safety and major environmental incidents in connection with offshore oil and gas operations have been identified, assessed, and reduced to a level as low as reasonably practicable (ALARP). One aspect of this involves determining the annual structural probability of failure for safety and environmental critical elements (SECEs) on offshore installations exposed to environmental loading. This is achieved by employing Structural Reliability Analysis (SRA). New knowledge about breaking waves has surfaced during the last decade which adds complexity to the SRA procedure. An SRA using crude Monte Carlo simulation considering breaking waves is described in this paper. The developed models are validated against physical model tests and other simulation methods. The process is complicated as numerous sources of uncertainty (both aleatoric and epistemic) are included. The aim has been to determine failure rates reflecting, as close as possible, the actual probability of failure (also denoted “actuarial”) by minimizing the epistemic uncertainties, as opposed to previous work, where, due to inadequacies in the various models, the failure rates were “notional”. The reader is provided a general overview only without going into details on the individual models due to the extent and complexity of the models.