Life-Cycle Cost Design Of Deteriorating Offshore Structures

A lifetime optimization methodology for planning the inspection and repair of structures that deteriorate over time is introduced and illustrated through numerical examples. The optimization is based on minimizing the expected total life-cycle cost while maintaining allowable lifetime reliability for the structure. This method incorporates with the quality of inspection techniques with different detection capabilities; the effects of aging, deterioration, and subsequent repair on structure reliability; and the time value of money. The overall cost to be minimized includes the initial cost and the preventive maintenance, inspection, repair, and failure. The methodology is illustrated using the tubular joint for offshore structure platform. An optimum inspection/repair strategy is developed for these tubular joints that are deteriorating due to corrosion in an aggressive environment. Ultimately, the reliability-based lifetime approach to developing an optimum inspection/repair strategy demonstrates the potential for cost savings and improved efficiency.