Probability of Failure for Fixed Offshore Structures Determination: An Analysis of a Braced Monopod and 4-Legged Platforms with Respect to Industry Standards

Abstract

The structural integrity is susceptible to a combination of statistical and engineering design uncertainties that may remain flexible as long as the structure can successfully manage the encountered load. There are many methods for determining the probability of failure (POF) in the oil and gas sector, but they all have particular constraints. Therefore, this study is a quantitative risk assessment to establish a more reliable method for calculating the POF value. This study chose and evaluated a sample of a braced monopod and 4 legged offshore structures for global non-linear analysis. The most reliable form of distribution was predetermined, and the appropriate integral equation was applied and computed based on the load and strength model conditions. The result of the testing of stress-strength interference for 12 directions and for 8 directions of wave impact in POF indicated that the platform remained intact and reliable compared to the L2 exposure level for the reliability target of POF recommended by ISO 19902, ISO 19901, and PETRONAS. Furthermore, this established that the applied integral equation provided a high degree of confidence in calculating the new POF. This newly created approach will enable the structural engineer to outline action items as part of the organisation’s risk management process.