Evaluation of Online Container Stacking Strategies Using Simulation

With the current increase of container traffic volumes around the globe, it becomes ever more important to have efficiently running container terminals. In this thesis, we investigate two concepts with which to increase efficiency, and compare them to several benchmark algorithms, using a Java-based discrete-event simulation tool. The first concept is to use any knowledge known about container departure times, in order to limit the number of reshuffles. We stack containers leaving shortly before the previous on top of each other. The second is the evaluation of the tradeoff between stacking further away in the terminal vs. stacking close by the exit points and accepting more reshuffles. We have formulated several strategies based on these concepts, some of which mix the two. We compare the strategies derived from these concepts primarily by looking at the exiting time of containers, and secondarily by looking at reshuffle occurrences, ground position usage, entry time and crane workload. It is concluded that even the use of imperfect or imprecise departure time information leads to significant improvements in efficiency. Minimizing the difference in departure times proved to be very important. It was also found that the tradeoff between stacking further away in the terminal vs. stacking close by the exit points and accepting more reshuffles leads to improvements over the benchmark.