The Containership Loading Problem
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The Containership Loading Problem AKIO IMAI1, ETSUKO NISHIMURA1, STRATOS PAPADIMITRIOU2 & KAZUYA SASAKI1 1 Department of Transportation and Information Systems Engineering, Kobe University of Mercantile Marine, Fukae, Higashinada, Kobe 658-0022 Japan; 2Department of Maritime Studies, University of Piraeus, 40 Karaoli & Dimitriou Str. GR-185 32 Piraeus, Greece. E-mail: [email protected]
The efficiency of a container terminal depends primarily on the smooth and orderly process of handling containers, especially during the ship's loading procedure. The loading plan is mainly determined by two considerations: ship stability and minimum number of rehandles required. These two basic considerations are often in conflict. Most containerships have a cellular structure, imposing a strong restriction on the order of the container loading sequence. To preserve a ship's stability, some containers may be stowed in a ship hold in middle vertical locations. A similar loading problem exists in the stacking of yard containers. If these containers are stacked in the yard under others which are to be picked up later, then the loading process requires a number of container rehandles. This paper is concerned with a ship's container load planning which satisfies these two considerations and minimises the number of rehandles. International Journal of Maritime Economics (2002) 4, 126-148. doi:10.1057/palgrave.ijme.9100041
Keywords: Container transportation; load planning; ship stability; container rehandling.
INT RODUCT ION The overwhelming majority of general cargo is nowadays containerised. Given that the containerised transportation system is capital-intensive, fast turnaround times in a container terminal are essential for the economic performance of liner shipping companies. Shortening the transit time of containers in the yard results
Akio Imai et al. The Containership Loading Problem
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in faster turnaround times of ships and consequently reduces the overall transit time of the entire transport chain, which had prompted the introduction of the container transportation system in the first place. The turnaround time of a ship includes the time for berthing, unloading, loading, and departure. The major activities affecting the turnaround time are the unloading and loading processes. While there is a relationship between the two processes, they are substantially carried out as two independent tasks with loading being the more difficult and sensitive to the efficiency of the operation. This paper develops an algorithm for efficient container ship load planning. The efficiency of the loading operation depends primarily on the loading sequence of the containers. Planning an efficient load sequence is not easy: Most container ships feature a cellular structure, designed for improving the container stowage function, which however imposes a strong restriction on the order of the loading sequence of the containers to be handled. If, for example, specific containers (referred to as target containers) must be stowed at vertically m
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