The Simultaneous Optimization Of Ship Deployment And Container Allocation In Container Liner Service

The temporal and spatial fluctuations of freight demand is the major operation risk that the shipping liner companies are faced with during the container liner operating process. In the time dimension, slack season and busy season exist in cargo transportation within one year, which directly affect the company’s decision to determine the ship size; in the spatial dimension, the freight demand and the flow direction among ports are imbalanced, which leads to the imbalance of container distribution, thereby the empty container repositioning and the container leasing problems are initiated.Undoubtedly, the fluctuations of freight demand forms a huge conflict with the requirement of liner service stability. To maximize the capacity of the shipping supply and to ensure effective control of operating risks, liner companies must simultaneously consider asset allocation from the macro and micro levels, and the key to the asset allocation is the reasonable composition of ship deployment and container constitution. In allusion to the instability of freight demand, the liner company can alter the ship number or change the ship size to adjust the shipping supply in macro level, and determine the container allocation and constitution to tune the shipping supply in micro level. Only optimizing the ship deployment and the container allocation and constitution simultaneously, can the shipping supply achieve the best control effects.Based on the equilibrium operation theory, this paper fully considered the fluctuations of freight demand characteristics. By distinguishing the difference of own ship and hired ship, the own container and hired container in use cost and idle risk, a ship deployment and container allocation simultaneous optimization model was formulated, with the objective of maximizing the annual profit in an appointed shipping line. Through a numerical experiment in a non-ideal circular liner route with5ports, the simultaneously optimized results of ship deployment, namely ship size, ship number, and the container allocation, namely container number, container constitution, container leasing strategy were obtained under the solver Lingo11. The results showed that the annual profit in the simultaneous optimization model was 55.34%higher than the profit in the average demand situation, and the optimized effect was more obvious with the fluctuation being bigger, which verified the simultaneous optimization model was valid and feasible.