Life cycle cost analysis of ageing structural components based on non-destructive condition assessment

Inspection-based maintenance strategies can provide an efficient alternative for ageing civil engineering components subjected to ageing and degradation. The technical and/or economic efficiency of such strategies depends on many factors, such as the mechanisms involved in the loss of performance; the availability, cost and efficiency of inspection techniques; the relation between what can be measured through inspections and the level of performance of the structure; the level of required serviceability of the structure; and the direct and indirect economic losses due to a reduction in the performance of a structure. On this basis, it is studied here, using Monte Carlo simulations, the benefits and limitations of an inspection-based maintenance strategy. The quality of the inspection technique is analysed in terms of its sensitivity to defects in their initial stage of development, and on its discriminant ability (detection of a real defect, while avoiding false alarms). This study is carried out with ageing characteristics, inspection models and cost assumptions that can cover a wide field of ageing assets. The influence of several factors is highlighted to see how they influence optimal strategies; a focus is given on the quality of inspections and on the allowable probability of failure.