Efficient stacking strategy in a container terminal is an essential task affecting competitiveness in many seaports, especially because this singular action may influence many of the conflicting objectives like minimizing the reshuffles (unproductive moves), the number of future relocations of containers in storage yard and maximizing the yard density and stacking area capacity utilisation. Any delay or deficiency in the synchronization and sequencing of daily operations and activities between seaside and landside of terminal will affect the stacking process in the container yard and may lead to the interference of terminal operations and lack of control in the scheduling of concurrent operations and activities during the management of inbound and outbound containers.

In this paper, we model a seaport container terminal as a queuing system to obtain the service level parameters. A multi-server queue in tandem consisting of three stages was considered, the first stage being the relations between the arrival containers or the inbound containers at seaport and the handling-off process, the second stage being the relations between the handling-off process and the transportation process, the third stage being the relations between transportation process and stacking process. Also, we consider twenty different scenarios of container stacking inside a container terminal to evaluate the performance of the queuing model. These scenarios vary from each other in terms of quantities of containers, durations of stay for the vessels in the seaport and number of equipments (quay cranes, yard trucks and yard cranes) that are used to perform the operations.

Experimental results were obtained from using the queuing model to evaluate the performance of the seaport container terminal operations, and to understand the behavior and characteristics of container stacking problem in a container yard.

In general, the experimental results show that when the value of the arrival rate approaches the value of service rate at the first service station, the waiting times of containers in the queue and in the system are increased compared to the waiting times of containers for the scenarios with a significant difference between values of the arrival rate and service rate of the first service station in a container terminal. Also, there is direct proportionality between the utilization factor of the handling-off station  and the average waiting times of containers in the queue (W_Q) and system (W_ct). The multi-server queues in tandem approach contributes effectively to solving the problem and gives a clear perception of how to support the decision makers in using different strategies for container stacking with many types and numbers of equipment to perform all operations and functions inside seaport under different durations of stay for the vessels in the seaport.

Keywords :

Container stacking, Queuing theory, Multi-server queues in tandem.