A STOWAGE PLANNING MODEL FOR MULTIPORT CONTAINER TRANSPORTATION
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The ship turnaround time at container terminals is an important measure of a port's efficiency and attractiveness. The speed and quality of load planning affect the length of turnaround time considerably. Container operations are extremely important from an economic standpoint, making them a prime target for productivity improvements. In addition, load planning is a very complex problem, since the planners have to account for the stability of the ship and rely on a variety of other stochastic processes.
Unfortunately, the load-planning problem is NP-hard making it difficult to obtain an optimal solution in polynomial time. Heuristics that trade quality for tractability are therefore promising tools when coping with this problem. Efficient load planning is accomplished by formulating the stowage-planning model to minimize extra shifting as a mixed integer-programming problem.
The key contributions of this dissertation are as follows.
A mathematical model is developed which considers real life constraints and considering loading/unloading along the entire voyage.
A second mathematical model is formulated to obtain a lower bound on the value of the objective function of the exact solution.
A heuristic procedure is developed that is guide by practical considerations that account for the structure of the stowage-planning problem.
All proposed mathematical models and heuristic are validated with experimental results. In all cases, these results demonstrate the stability, flexibility and efficiency of the model, and establish its potential as a versatile and practical method for large scale container loading.