Container Ship Stowage Planning with Quay Crane Utilization
Because of higher competition among ports in recent years, improving the efficiency has become an important issue in containership operations. One of the measures of performance is berthing time at port which is determined by the arrangement of containers both within the container terminal and on the containership. Most of the berthing time of a containership consists of unloading and loading time of containers. Determining an efficient configuration of containers that facilitates this process is an everyday problem solved by ship planners.
This research deals with the containership stowage planning problem which is the problem of stacking containers on different bays of a containership that visits several ports during a voyage. Containers may have difference types, sizes, weights and destinations. At each port quay cranes unload the import containers from and load the export containers onto the ship. Since the stacks are accessible only from the top, for unloading an individual container all the containers on top of it must be unloaded first. If the top containers have a different destination they must be loaded back onto the ship. Each of these extra movements is called a shift or re-handling which increases both the operational cost and ship turnaround time. In addition to that if the distribution of containers among the bays matches the configuration of available quay cranes at each port, the cranes can operate on the ship more efficiently. The stability of the containership must be retained during the voyage.