Optimizing container movements using one and two automated stacking cranes

Productivity of a sea port depends, in part, on stacking cranes working in blocks of its storage yard. Each container leaving a block must be moved by a storage-yard crane to a buffer zone during a specific time window so it can reach its destination on time. Containers entering a block for storage must be moved out of the buffer zone sufficiently soon to avoid overflow. In this paper, we formulate integer linear programs to prescribe movements to transport and stack containers in storage yards using one and two equally-sized Automated Stacking Cranes (ASCs) working with straddle carriers. Using real world data, we construct test problems varying both the number of container bays and fullness of the block. We find that one ASC working alone requires up to 70% more time than two ASCs working together to accomplish the same container movements. Optimal solutions of the integer linear programs are typically obtained in only a few seconds.