Reliability Considerations in Offshore Platform Criteria

A fundamental objective of offshore platform design is to configure and construct a structure that will have utility, desirable performance, adequate reliability, and reasonable cost. This paper examines reliability considerations involved in development of environmental criteria for offshore platforms. For a given structural criteria, a simple reliability formulation is developed to determine design wave heights or design ground accelerations and their return intervals. Three examples are developed: design wave heights and return intervals for conventional template-type, deep water platforms in the Gulf of Mexico and Baltimore Canyon, and design wave heights and effective ground accelerations for similar platforms in the Gulf of Alaska. Return interval is found to be a highly sensitive parameter for specifying design environmental conditions. The use of a range of target Safety Indices is proposed in lieu of return period.