Planning Housekeeping Operations at a Maritime Container Terminal

Housekeeping operations are yard-to-yard movements of containers inside a transshipment terminal. Usually the ow of containers in a transshipment terminal follows the quay-yard-quay cycle. Actually the ingoing containers are unloaded from the containerships and transferred to dedicated yard blocks, where they are stacked. Outgoing containers ow in the opposite direction. However sometimes further container movements are needed, either to speed up the unloading/loading operations, or to reorganize the stacking spaces during the time-of-staying of the containers in the yard. The ingoing containers, for example, can be rst placed into yard buers in front of the berths where the containerships are moored and then transferred to the dedicated yard blocks. Similarly groups of containers already stacked in the yard could be moved to dierent blocks, so as to minimize the fragmentation of the available stacking spaces. In this talk we are concerned with the planning of the housekeeping operations occurring before the loading phase. Starting from the stowage plan of a containership, our aim is to decide which containers, among the outgoing ones, must be moved to the buer areas, so as to minimize the runtime costs, in terms of the total distances traveled by the terminal vehicles during the loading phase. We propose a 0-1 Linear Program, a Lagrangean decomposition scheme, and a dual ascent procedure for the optimization of the Lagrangean Dual.