Simulation-based optimization for the quay crane scheduling problem

Maritime terminals of pure transhipment are emerging logistic realities in long-distance containerized trade. Here, complex activities of resource allocation and scheduling should be optimized in a dynamic, non deterministic environment. The assignment of expensive quay cranes to multiple vessel-holds for container discharging and loading operations is a major problem, whose solution affects the operational performance of the whole terminal container. In OR literature, this problem is known as the quay crane scheduling problem. With the objective of minimizing the vessel's overall completion time, we first give our IP formulation and then, under the more realistic assumption that discharge-loading times are non deterministic, we focus on a simulation-based optimization approach which embodies the IP formulation. Two different simulation optimization algorithms are tailored to the problem: simulated annealing and adaptive balanced explorative and exploitative search. Preliminary numerical results are presented on real vessel data.