Pre-earthquake multi-objective probabilistic retrofit optimization of bridge networks based on sustainability

Planning retrofit actions on bridge networks under tight budget constraints is a challenging process. Because of the uncertainties associated with this process, a probabilistic approach is necessary. In this paper, a probabilistic methodology to establish optimum pre-earthquake retrofit plans for bridge networks based on sustainability is developed. A multicriteria optimization problem is formulated to find the optimum timing of retrofit actions for bridges within a network. The sustainability of a bridge network and the total cost of retrofit actions are considered as conflicting criteria. The sustainability is quantified in terms of the expected economic losses. The uncertainties associated with seismic hazard and structural vulnerability are considered. The methodology is illustrated on an existing bridge network. Genetic algorithms are used to solve the multicriteria optimization problem. The effects of deterioration on bridge seismic performance are considered. The effects of the time horizon on the Pareto optimal solutions are also investigated.