Aisle Designs for Unit-Load Warehouses with Multiple Pickup and Deposit Points

Abstract

This thesis focuses on unit load warehouses having multiple pickup and deposit (P&D) locations on the warehouse dock(s) — i.e., a P&D region. Our aim is to design a cross aisle structure that will reduce the cost of operating a unit load warehouse. We concentrate on the labor cost of material handling, or more specifically, on the travel cost associated with unit load putaway and retrieval. We define two “candidate shapes.” Namely, the Flying-V shape and Lambda shape. We state a nonlinear optimization problem to find an improved cross aisle configuration by minimizing the expected cost of a single pickup and retrieval task. We separately carry out optimization for each candidate shape and choose the more economical one. Our results are a sort of worst case analysis for the designs we consider and the benefits from our solutions range typically from 3% to 6.5%.

The second part of this thesis is concerned with applications of the same design principles to floor storage. A less rigorous, but effective approach is developed. We devise a number of aisle and lane designs and apply them to a realistic setting.