A decision-tree stacking heuristic minimising the expected number of reshuffles at a container terminal

Abstract

Reshuffling containers, one of the daily operations at a container terminal, is time consuming and increases a ship's berthing time. We propose a decision-tree heuristic to minimise the expected number of reshuffles when arriving containers should be stacked in a block of containers with an arbitrary number of piles. The heuristic algorithm uses the optimal solutions of a stochastic dynamic programming model. Since the total number of states of the dynamic programming model increases exponentially, the model can only solve small-scale problems in a reasonable time. To solve large-scale problems, the heuristic uses the results of the exact model for small-scale problems to generate generalised decision trees. These trees can be used to solve problems with a realistic number of piles. The numerical experiments show the effectiveness of the algorithm. For small-scale problems, the trees can quickly make optimal decisions. For large-scale problems, the decision-tree heuristic significantly outperforms stacking policies commonly used in practice. Using the decision trees, we can compare the performance of a shared-stacking policy, which allows containers of multiple ships to be stacked on top of each other, with a dedicated-stacking policy. Shared-stacking appears to outperform dedicated-stacking.

Resequencing with parallel queues to minimize the maximum number of items in the overflow area

“…Due to the comparatively long dwell time of containers, however, there is usually a lot of uncertainty with regard to the exact departure time of each box. Thus, existing research on the loading problem in ports either focuses on simple online stacking rules evaluated by simulation (see [5,14]) or minimizes the expected number of reshuffles, for example, by considering probability distributions of different weight classes which mainly influence the retrieval time (see [18,21,24,35]). Similar problems are to be solved in conventional warehouses where pallets are stockpiled in ground-storage (e.g., [29]).…”

A Heuristic Procedure for the Outbound Container Relocation Problem during Export Loading Operations

“…More recently, Gharehgozli et al [20] develop a decisiontree heuristic and a dynamic programming model focusing on minimizing the expected number of relocations when arriving containers should be stacked in a block. For smallscale problems with a small number of piles, they compare the decision-tree heuristic with the dynamic programming model results and they use the dynamic programming model to solve large-scale problems.…”

A Fuzzy Logic Model for the Container Stacking Problem at Container Terminals

“…A real time container storage system is presented by [30], and a discrete event simulation model of a vessel-to-vessel transshipment terminal to show the impacts of yard storage allocation on the overall productivity of the container terminal, measured as the gross crane rate (number of lifts per quay crane hour). A decision-tree heuristic is proposed by [13] to minimize the expected number of reshuffles when arriving containers that should be stacked in a block of containers with an arbitrary number of piles. The authors compare shared and dedicated storage policies and results show that sharedstacking outperforms dedicated-stacking.…”