Optimizing Maintenance Interventions for Deteriorating Structures Using Cost-Benefit Criteria

Life extension of existing deteriorating structures requires maintenance interventions, which allow partial or complete rehabilitation. However, such maintenance interventions have to be economically reasonable, i.e., maintenance expenditures have to be outweighed by expected future gains. If this cannot be achieved, the optimal lifetime of a structure has been exceeded. This paper discusses optimum maintenance planning (optimal sequences of maintenance times and rehabilitation levels) by maximizing the expected net present benefit rate throughout lifetime. The underlying formulation is as follows: (1) between maintenance interventions the deterioration due to Poisson shocks is modeled by a continuous-time Markov chain; (2) maintenance interventions can take place anytime throughout the lifetime and comprise the rehabilitation of all deterioration states above a certain minimum level; and (3) maintenance interventions are optimized by taking into account all life-cycle costs (construction, failure, inspection, and statedependent rehabilitation costs as well as state- or time-dependent benefit rates). Numerical examples demonstrate that the proposed approach not only allows to optimize maintenance interventions, but also allows to determine optimal lifetimes and acceptable failure rates.