Yard storage planning for minimizing handling time of export containers

We consider multiple factors of allocating yard storage space to export containers in a terminal under heavy workloads and with a limited yard storage capacity. We aim at expediting container handling in yards and thus we attempt to balance workloads, shorten yard-to-berth transport distances and minimize the number of sub-blocks with handling jobs. To tackle various objectives in this yard storage allocation, we introduce a hierarchical analytical method that decomposes the planning procedure into two stages. We first optimize workload distribution across the whole yard. Thereafter, we propose a flexible yard allocation strategy and attempt to stack export containers into a minimum number of sub-blocks in the yard so as to facilitate yard crane operation and increase yard space utilization. We present integer programming formulations for these two sub-problems and then solve these two models iteratively by introducing additional parameters and constraints into the formulations. Experimental results indicate that this method is efficient and effective in obtaining good storage templates in the yard by achieving minimum handling time for export containers. Further discussions explore the results of yard space utilization and busy rate in yard blocks when providing different sizes of sub-blocks that contributes to the setting up of suitable sub-blocks in a terminal according to the capacity of its storage space and container handling devices.