Life-Cycle Cost-Effective Optimum Design of Ice-Resistant Offshore Platforms

In China, the oil and natural gas resources in Bohai Bay are mainly marginal oil fields, which freeze in the winter. It is necessary to build both ice-resistant and economical offshore platforms. However, risk is involved in the design, construction, utilization, and maintenance of offshore platforms as uncertain events may occur within the life-cycle of a platform. In this paper, the optimum design model of the expected life-cycle cost for ice-resistant platforms based on the cost-effectiveness criterion is proposed. Multiple performance demands of the structure, facilities and crew members, associated with the failure assessment criteria and evaluation functions of costs of construction, consequences of structural failure modes including damage, revenue loss, death, and injury, as well as discounting cost over time are considered. Different reliability analysis approaches involved in life-cycle cost evaluation, such as the global reliability under the extreme ice load, the dynamic reliability, and fatigue life induced by ice vibration, are studied. The proposed life-cycle optimum design formulas are applied to a typical ice-resistant platform in Bohai Bay, and the results demonstrate that the life-cycle cost-effective optimum design model is more rational compared with the conventional static design and the optimum dynamic design.