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Natural disasters and their impacts on human’s life are one of the most important concerns of our societies. Infrastructures such as power systems, water distribution systems, transportations, communication systems and gas networks are among the main components of urban environment. There are interdependencies among infrastructures and their subsectors. Infrastructures performance in disasters have significant role in reaching to a disaster resilient society. The uncertainty in vulnerability assessment of these lifelines in one hand and the lack of proper planning for recovery and selection of optimized strategies for different sectors on the other hand, may result in a great losses. Iran is located in a seismic active zone and has always been faced with devastating earthquakes. Tehran, the capital of Iran, is at seismic risk, since it sits on major active faults and suffers from techtonic activities. However, poor construction practices, and having large population, makes Tehran more vulnerable to earthquakes. Accordingly, it becomes necessary to have proper recovery plan beforehand based on accurate seismic performance modeling of interconnected infrastructures. Optimal financial resource allocation to the seismic retrofitting of the infrastructures and specifying their priority are considered as prominent issues in the macro scale decision making process. As the optimum strategy is adopted and the budget allocation is performed with the appropriate priority, it is expected that a significant loss reduction is achieved. When the financial resources are limited, allocating based on the proper priority seems to be more vital. The study tries to find out the economic effect of infrastructures’ interdependencies using Leontief Input-Output Model based on the matrix of value of commodity flow among different sectors. Tehran is chosen as a case study. In this work, the optimum strategy for retrofitting the infrastructure networks as the water, transportation, communication, gas, and power infrastructures is investigated using Uncertainty Dynamic Inoperability Input-Output Model (U-DIIM). This optimum strategy is adopted against the earthquake impacts in terms of the indirect economic losses, sensitivity to the parameters of the commodity flow matrix and cost of retrofitting strategy. Therefore, the indices employed in this research include reducing the economic losses and also the sensitivity with respect to the costs associated with the conduction of the strategy. By minimizing the total economic loss, sensitivity to economic loss parameters and cost of implementation of strategies, the best optimal scenario is selected for retrofitting strategy. The strategy selection is based on initial inoperability, recovery time and demand perturbation after earthquake. The Pareto method is also used in this work to select the optimal retrofitting strategy. The results reveal that increasing the seismic performance of the infrastructures by 25% is the optimum retrofitting strategy from the economic point of view. Following this strategy, the ratio of economic loss reduction to the strategy implementation costs and also the ratio of the sensitivity reduction to the strategy implementation costs are 0.3996 and 3.66, respectively. It is worthwhile to note that all economic interactions between the infrastructures are taken into account in the research. The proposed methodology may be used for the optimal selection of the other set of infrastructures in an uncertain situation.

Keywords: Infrastructure, Earthquake, Retrofitting, U-DIIM, Prioritizing retrofitting strategy.

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