This thesis considers three network design problems for a given network service area partitioned into a certain number of predetermined zones, which arise in many network service areas including telecommunications, logistics, and transportations. Chapter 2 and Chapter 3 deal with a hub-and-spoke network which has played an important role in modeling many practical networks in recent decades. Chapter 4 considers an uncapacitated facility location problem subject to the distance constraints.
In Chapter 2, a hub-and-spoke network design problem is considered under the nonrestrictive policy. The objective is to design a hub-and-spoke network by determining all the required hub locations in the predetermined zones and also all the terminal routes such that the sum of hub construction cost and flow transportation is minimized. The complexity of the problem is proved to be NP-complete in the chapter. By characterizing a special structure of the problem, a dual-based solution approach (known to be effective for network design) is derived.
Chapter 3 considers a hub-and-spoke network design problem with link opening cost allowed. The problem is divided into two subproblems each to be solved independently. With the solution obtained from each subproblem, a combining procedure of the two solutions is then proposed to improve the whole solution.
Chapter 4 describes an uncapacitated facility location problem subject to distance and budget constraints. In the problem, the quality of service is measured in terms of delivery time (or distance) required from its nearest supplying facility. The objective of the problem is to determine the appropriate number of the required supplying facilities and their locations so as to minimize the total delivery cost under the service quality and budget constraints on setting up the supplying facilities. To solve the problem, a branch and bound algorithm using the Lagrangean Relaxation bound is proposed with a preprocessing ...