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

There are many sources of risk affecting the network elements may lead to network failure, so 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 to 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 efficacy of the proposed solution approach comparing to classical solution approaches in large- scale problems. moreover, the superiority of the proposed model is confirmed by comparing to the classical models.