| Storage facilities, including warehouses, distribution centers and container terminals, can be found everywhere. They form the key nodes in supply chain networks decoupling demand from supply in time and quantity, and are particularly important for the Netherlands which serves as a gateway to a large population in Western-Europe. Due to the rapid increase of international trade, outsourcing and production offshoring the land needed for the related supply chain activities has become short. Lack of space has driven companies to come up with innovative compact (or 3D) storage concepts for unit-loads (e.g. pallets, totes, containers), saving much footprint. A compact storage system stores unit-loads multi-deep, but still allows them to be accessed individually. Such systems bring many new managerial challenges. At strategic level, the challenges include facility layouts (e.g. number and sizes of storage racks, number of cranes (storage/retrieval or S/R- machines), and the position of the depots). At operational level, the challenges include how to store and retrieve products from storage racks, and how to sequence storage and retrieval jobs to timely satisfy customers orders. To resolve these challenges, the aim of this project is to minimize the response time (e.g. unit-load throughput time or make-span) of compact storage facilities, by determining optimal layout and operations. Several models will be proposed for throughput time approximation (probabilistic models), and storage and retrieval job sequencing (integer programming models and simulation models). These models can in turn be used for facility optimization. |
