At a maritime container terminal, containers discharged from a vessel are usu- ally stored in the yard, and then loaded on different vessels. The storage phase allows to decouple in time the ingoing and outgoing container flows. Therefore, if the sojourn time of the containers (dwell-time) in the yard is sufficiently long, the discharging and loading operations are independent, so that they can be planned and scheduled separately and efficiently. On the other hand high dwell- times represent a drawback for the terminal management as well as for the shipping operators. Actually the former would increase the terminal through- put by reducing the dwell-times, and the shipping operators would reduce the port fees. This amounts to say that short dwell-times is a common target for the two main operators of the transhipment market. In view of that, the terminal planners are considering the feasibility of a new operational modality, called live connection. In this modality a discharged container is immediately transshipped to the outgoing vessel, completely skipping the yard storage phase. Here we are concerned with the case of two vessels, simultaneously berthed at not necessarily adjacent berths, given that sufficient terminal resources (ma- chines and operators) have been previously allocated. We assume that some of the containers discharged from each of them must be directly loaded into the other, while the rest of the cargo follows the conventional transshipment flow (quay-yard-quay). Clearly in the direct transhipment modality the unloading and loading operations are no longer independent and the related scheduling processes are concurrent: the same container represents two dependent tasks, to be executed by different machines (quay cranes) operating on different ves- sels, linked by a strict precedence relationship. Our aim is to schedule all the vessel operations and decide the stowage positions for the containers directly transshipped, so as to minimize their waiting time and the overall service time of the vessels. For this problem we review a Linear Integer model proposed in [1], propose some advances in the solution procedure based on the Tabu Search paradigm and discuss the numerical experience.
Modelling and solving the direct ship-to-ship container transshipment problem
2016
Abstract
At a maritime container terminal, containers discharged from a vessel are usu- ally stored in the yard, and then loaded on different vessels. The storage phase allows to decouple in time the ingoing and outgoing container flows. Therefore, if the sojourn time of the containers (dwell-time) in the yard is sufficiently long, the discharging and loading operations are independent, so that they can be planned and scheduled separately and efficiently. On the other hand high dwell- times represent a drawback for the terminal management as well as for the shipping operators. Actually the former would increase the terminal through- put by reducing the dwell-times, and the shipping operators would reduce the port fees. This amounts to say that short dwell-times is a common target for the two main operators of the transhipment market. In view of that, the terminal planners are considering the feasibility of a new operational modality, called live connection. In this modality a discharged container is immediately transshipped to the outgoing vessel, completely skipping the yard storage phase. Here we are concerned with the case of two vessels, simultaneously berthed at not necessarily adjacent berths, given that sufficient terminal resources (ma- chines and operators) have been previously allocated. We assume that some of the containers discharged from each of them must be directly loaded into the other, while the rest of the cargo follows the conventional transshipment flow (quay-yard-quay). Clearly in the direct transhipment modality the unloading and loading operations are no longer independent and the related scheduling processes are concurrent: the same container represents two dependent tasks, to be executed by different machines (quay cranes) operating on different ves- sels, linked by a strict precedence relationship. Our aim is to schedule all the vessel operations and decide the stowage positions for the containers directly transshipped, so as to minimize their waiting time and the overall service time of the vessels. For this problem we review a Linear Integer model proposed in [1], propose some advances in the solution procedure based on the Tabu Search paradigm and discuss the numerical experience.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
