Truck scheduling and storage allocation, as two separate subproblems in port operations, have been deeply studied in past decades. However, from the operational point of view, they are highly interdependent. The processing time of discharging a container by a truck is composed of travel time spent in the network and the time waiting for the service of yard cranes and quay cranes. If a container is allocated to a yard block far from its unloading ship, the travel time will increase; whereas if too many containers are allocated to the yard block close to their unloading ship, the waiting time will increase due to the limitation of mechanical performance of yard cranes. Storage allocation for import containers has to balance the travel time and waiting time of each container, so that the time ships spent at the terminal can be reduced. This paper proposed an integer programming model handling these two problems as a whole. The objective of this model is to reduce congestion and waiting time of container trucks in the terminal so as to decrease the makespan of discharging containers. Since the truck scheduling and storage allocation problem is NP-hard, a genetic algorithm and a greedy heuristic algorithm are designed to attain near optimal solutions. It shows that the heuristic algorithm can achieve the optimal solution for small-scale problems. The solutions of small- and large-scale problems obtained from the heuristic algorithm are better than those from the genetic algorithm.
Abstract