Space-efficient layouts for block stacking warehouses

Abstract

In block stacking warehouses, pallets of Stock Keeping Units (SKUs) are stacked on top of one another in lanes on the warehouse floor. A conventional layout consists of multiple bays of lanes separated by aisles. The depths of the bays and the number of aisles determine the storage space utilization. Using an analytical model, we show that the traditional lane depth model underestimates accessibility waste and therefore does not provide an optimal lane depth. We propose a new model of wasted storage space and embed it in a mixed-integer program to find the optimal bay depths. The model improves space utilization by allowing multiple bay depths and allocating SKUs to appropriate bays. Our computational study shows the proposed model is capable of solving large-scale problems with a relatively small optimality gap. We use simulation to evaluate performance of the proposed model on small to industrial-sized warehouses. We also include a case study from the beverage industry.

Keywords:

• Facility layout
• warehouse design
• block stacking
• space utilization
• optimal lane depth

Additional information

Notes on contributors

Shahab Derhami

Shahab Derhami is a senior research scientist in School of Industrial and Systems Engineering at Georgia Tech. He received his BS in industrial engineering from Azad University-South Tehran, MS in social and economic systems engineering from Bu-Ali Sina University, and ME and PhD in industrial and systems engineering from Auburn University. His research interests are in developing descriptive, predictive, and prescriptive methodologies to analyze, design, and improve facility layout, supply chain, logistics, and transportation systems in manufacturing and service sectors.

Jeffrey S. Smith

Jeffrey S. Smith is the Joe W. Forehand Professor of Industrial and Systems Engineering at Auburn University. His research and teaching interests include simulation modeling and analysis, manufacturing system design, and analytics for operations. He has served as the WSC Business Chair (2010) and General Chair (2004) and is currently on the WSC Board of Directors. He has a BIE from Auburn University and a MS and PhD (both in industrial engineering) from Penn State University.

Kevin R. Gue

Kevin R. Gue is a professor of industrial engineering and Scientific Director of the Logistics and Distribution Institute at the University of Louisville, USA. He graduated from the U.S. Naval Academy in 1985 with a Bachelor's Degree in mathematics and received his MS and PhD degrees from the School of Industrial & Systems Engineering at Georgia Tech. Previously he held appointments at Auburn University and at the Naval Postgraduate School. Dr. Gue's research interests include modeling and control of logistics systems, with applications in distribution, warehousing, and material handling. He is a past president of the College-Industry Council on Material Handling Education.