Methodology for the analysis of risks during the construction and installation phases of an offshore platform

This paper describes the development and application of a quantitative method for the assessment of risk of asset loss due to structural damage during the construction through to installation phases of an offshore concrete gravity-base structure. Risk criteria, embodying the 'ALARP' principle, are developed for different degrees of platform damage, expressed as asset loss. Initiating events leading to possibly significant failure modes are identified and quantified, mostly using fault trees. Much of the effort has gone into identifying and quantifying human error frequencies, including those for recovery failure, based on detailed scrutiny of the operations and established human factors methodologies. Outcome modelling for the initiating events uses an event tree approach, and the detail in the consequence modelling, e.g. for modelling of structural damage, is commensurate with the expected risk as identified in a 'first pass' analysis. Risk-reduction measures are targeted at dominant risk contributors, whose principal determinants can be identified from the fault trees. The application of the method to the analysis and mitigation of dropped-object risks during certain construction phases of the platform is described.