Vertical Expansion: A Solution for Future Container Terminals

Container terminals play a major role in the growth of international trade. They need to accommodate the increasing number of containers while their space is limited. One approach, often used in practice, is horizontal expansion through expensive land reclamation projects. In contrast, vertical expansion uses the available land more efficiently by storing containers in high-bay warehouses. Leading world container ports have studied and developed several types of container warehouses which have been introduced in this paper. In addition, we focus on a specific type of next generation container terminals consisting of container towers. We investigate several design questions: 1) What is the optimal configuration of a container tower? 2) How does a container tower compare to a traditional container block in terms of performance? 3) Is a container tower financially feasible compared to an existing container block? 4) What are the impacts of varying design parameters on the container tower performance and its financial feasibility? Question 1 is answered by obtaining closed-form expressions for the tower travel time, formulating the problem as a nonlinear optimization model, and deriving closed-form expressions for the tower optimal configuration. Questions 2 and 3 are answered by using closed-form expressions in order to compare the performance of two systems. Question 4 is answered by a sensitivity analysis for the design parameters of the container tower. The results show that, compared to a traditional container block, the container tower can increase the annual throughput, while saving on the required footprint at competitive investment costs.