Resilient network design in a location-allocation problem with multi-level facility hardening

Many sources of risk affect network elements, which may lead to network failure; thus, planners need to consider them in the network design. One of the most important strategies for disruption risk management is the static resilience. In this strategy, the network functionality is maintained after the disruption event by the prevention and hardening actions. In this paper, a resilient capacitated fixed-charge location-allocation model is proposed. Both facility hardening and equipping of the network with backup facilities for disrupted elements are considered together to avoid supply network failure due to random disruption. Facilities are decided to be hardened in multiple levels before disruption events. The problem is formulated as a non-linear integer programming model; then, its equivalent linear form is presented. A Lagrangian Decomposition Algorithm (LDA) is developed to solve large-scale instances. Computational results confirm the high efficacy of the proposed solution approach, compared to classical solution approaches, in dealing with large-scale problems. Moreover, the superiority of the proposed model is confirmed in comparison to the classical models.