Maintenance scheduling of flood control plant under uncertainty based on multi-objective optimization

The drainage pumping plants are the main facilities in flood control infrastructure. Many of them have deteriorated and their maintenance, especially replacement, has become a large issue in Japan. The plant consists of many different types of equipment. Each of them has its own lifespan. The lifespan has uncertainty. A method is proposed to schedule the replacement of equipment under uncertainty, considering the two properties of rationality and robustness. The rationality means that the schedule is logical and feasible. It is evaluated by the replacement cost in the scheduling period under the constraints of the reliability and annual cost. The robustness means that the schedule is hard to be affected by the uncertainty of the equipment lifespan. It is evaluated by the expected value of the time difference between the actual replacement and the scheduled replacement based on the probability distribution of equipment lifespan. The problem is modeled as a multi-objective optimization one on the rationality and the robustness of the schedule. Pareto optimal solutions are derived. The effectiveness of the proposed method is illustrated by case studies based on the practical conditions. The characteristics of Pareto optimal solutions are made clear by comparing non Pareto optimal ones. The contribution of this paper is to propose a method to design the replacement schedule which is hard to be affected by the uncertainty of the equipment lifespan.