Inventory routing problems on two-echelon systems: exact and heuristic methods for the tactical and operational problems
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Inventory routing problems on two-echelon systems: exact and heuristic methods for the tactical and operational problems Katyanne Farias de Araújo © Springer-Verlag GmbH Germany, part of Springer Nature 2020
This is a summary of the author’s Ph.D. thesis supervised by Khaled Hadj-Hamou and Galliam Claude Yugma and defended on November 25, 2019 at the Université Grenoble-Alpes. The thesis is written in English and is available from the author upon request at [email protected]. This research was funded by the research program “ARC 2016 N.08 – Industrialisation et science du gouvernement” of the region Auvergne-Rhône-Alpes. This thesis deals with the development of efficient exact and heuristic methods to solve new variants of the Inventory Routing Problem (IRP) on two-echelon systems. Given a set of customers with demands over a time horizon, the IRP consists of determining routes and delivery quantities to meet customer demands at a minimum inventory holding and transportation costs. Transportation and inventory management activities have a great impact on each other. Ensuring an ideal inventory level for customers can require frequent deliveries and lead to high logistics costs. To optimize the trade-off between inventory and transportation costs, Vendor Managed Inventory (VMI) systems have been developed to manage inventory and transportation operations together. Besides, two-echelon systems have been studied aiming at improving the freight vehicle flow inside urban areas. As new management policies have emerged, with the goal of limiting the traffic of large vehicles and their speed in urban centers, Distribution Centers (DC) are introduced to coordinate freight flows inside and outside the urban areas. Products are then delivered from the suppliers to the customers through the DC. The stock of products in DC also has the advantage of reducing the transportation cost due to the reduced number of trips to suppliers. In this thesis, we propose to combine a two-echelon system with IRP. We introduce an Operational Two-Echelon Inventory Routing Problem (O-2E-IRP) which, to the best of our knowledge, is a new extension of the IRP. In the proposed O-2E-IRP, the customers must be served by a supplier strictly through DC and routes must be defined in both echelons over a given time horizon. Each DC must meet the demands of a set of customers, where the set of customers each DC must serve is given. Three different replenishment policies and routing configurations are modeled for this problem. We develop two Mixed Integer Linear Programming (MILP) formulations, and a Branchand-Cut (B&C) algorithm combined with a two-step matheuristic to solve the problem. In addition, we analyze several valid inequalities available for the IRP, and introduce new ones inherent to the IRP on two echelons. Extensive computational experiments
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were carried out on a set of randomly generated instances. The obtained results show that the performance of the methods is very dependent on the invent
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