Optimization of Repair and Recover of Infrastructure Systems Considering Life-Cycle Cost

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Up to the last year, research had been made on the definition of life-cycle cost and its application to the maintenance of infrastructure systems. An attempt was made to develop an optimal maintenance system using the concept of life-cycle cost. Furthermore, the system was improved for practical use and its applicability was demonstrated using the real data. Then, the reliability theory was introduced so as to deal with various uncertainties regarding the deterioration and environments.This year, it was intended to complete the system and provide us a practical maintenance plan which is reliable and sufficient for functionality. In order to handle the uncertainties, a new system was developed, which does not explicitly use the probability theory. Since the probabilistic method is often difficult for practitioners to understand, the system employed a new optimization method to deal with the uncertainties. Applying the genetic algorithm proposed by Tamaki et at., it is possible to introduce the effects of uncertain factors with respect to the prediction of deterioration and the change of environmental conditions without using the probability concepts. On the other hand, another system was developed, which can provide a practical solution for maintenance problems of large and complicated structures. Using the genetic algorithm based upon the concept of virus evolution, it can be done to obtain each maintenance plan for individual elements or members of a structure as well as the total maintenance plan for overall structure. This system can reduce the computation time and memory. Through the research, it is concluded that the calculation of user cost is quite important to estimate the life-cycle cost appropriately. Therefore, great attention was paid to the definition and calculation of user cost and their validity was proved by applying them to a road network in Hokkaido.