The budget constrained r-interdiction median problem with capacity expansion

In this article, we elaborate on a budget constrained extension of the r -interdiction median problem with fortification (RIMF). The objective in the RIMF is to find the optimal allocation of protection resources to a given service system consisting of p facilities so that the disruptive effects of r possible attacks to the system are minimized. The defender of the system needs to fortify q facilities of the present system to offset the worst-case loss of r non-fortified facilities due to an interdiction in which the attacker’s objective is to cause the maximum possible disruption in the service level of the system. The defender-attacker relationship fits a bilevel integer programming (BIP) formulation where the defender and attacker take on the respective roles of the leader and the follower. We adopt this BIP formulation and augment it with a budget constraint instead of a predetermined number of facilities to be fortified. In addition, we also assume that each facility has a flexible service capacity, which can be expanded at a unit cost to accommodate the demand of customers who were serviced by some other interdicted facility before the attack. First, we provide a discrete optimization model for this new facility protection planning scenario with a novel set of closest assignment constraints. Then, to tackle this BIP problem we use an implicit enumeration algorithm performed on a binary tree. For each node representing D. Aksen (B) College of Administrative Sciences and Economics, Koç University, Rumelifeneri Yolu, 34450 Sarıyer, Istanbul, Turkey e-mail: [email protected] N. Piyade · N. Aras Department of Industrial Engineering, Boğaziçi University, 34342 Bebek, Istanbul, Turkey e-mail: [email protected] N. Aras e-mail: [email protected]