This paper proposes a decision making methodology on an optimal inspection method/cycle for long span bridges, based on the two evaluation items: lifecycle cost and risk probability. Firstly, the authors formulate the aggregative Markov deterioration hazard model using visual inspection data, and propose a model for minimizing lifecycle cost. In addition, the authors express the risk of the management limit in the visual inspection of a long bridge with a fault tree, and calculate the probabilities of events constituting the fault tree with the Markov transition probability. Then, it becomes possible to grasp the variation in risk probability due to the difference in inspection and repair policies. Finally, the proposed method is applied to the actual case of determining an optimal inspection policy, to discuss its effectiveness empirically.

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 The present paper deals with evaluation and simulation of seismic system risk of intercity railway system. The analytical framework of the proposed method system combining reliability theory by means of minimum pass set and outage time evaluation considering seismic damage correlation is first formulated.
 Two series of numerical simulations; three basic models and simplified intercity railway system including parametric studies with regards to damage correlation, are then carried out. Major outputs of simulations such as seismic event risk curves of outage time of the system, recover process presentation in post-earthquake and bottleneck index of each unites are presented and discussed.

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