Study On Optimal Allocation Of Twin 40 Feet Quay Cranes In Container Terminals

Affected by the development of the global economic integration, global container trade showed a rapid growth. With the world's largest container ship Maersk Mc-Kinney Moller was put into operation in the Asia-Europe container ship route, world container transport officially entered the era of 18000TEU. In order to adapt to the trend of serving more large ships, twin 40 feet quay cranes are put into loading and unloading operation in several large container terminals in China, such as Shanghai. The use of twin 40 feet quay cranes can shrink the service time for ships, reduce operating costs and enhance the comprehensive competitiveness of the port. However, handling technology is different between twin 40 feet quay cranes and normal quay cranes. To maximize the advantages of twin 40 feet quay cranes on handling efficiency, ancillary equipment, staff and maintenance in the container terminals must be renewed, causing operating costs improved substantially. Therefore, majority of the container terminals mixed the use of twin 40 feet quay cranes and normal quay cranes for handling operation in our country, to maintain the competitiveness of handling large vessels and ensure operating costs can still be within a reasonable range at the same time. The allocation of twin 40 feet quay cranes are usually based on experience in our country, lack of scientific analysis. The purpose of this study is to solve this problem.By summarizing the handling technology of twin 40 feet quay cranes in container terminals, a system analysis on the operating procedures for container terminals is conducted. Operation costs for port and waiting costs for ships with configuration for twin 40 feet quay cranes are calculated in this paper. To minimize the total operation cost in the whole loading and unloading process, an optimal allocation model of twin 40 feet quay cranes in container terminals is conducted. To obtain the model parameters such as average number of ships in port, berth utilization efficiency of twin 40 feet quay cranes and berth utilization efficiency of normal quay cranes, a queuing model for different range of capacity is conducted. By application of queuing theory and Quasi-Birth-and-Death (QBD) theory, stationary distribution and queuing system characteristic index in the model are solved out. The correctness of the calculation results of queuing model for different range of capacity is verified by comparing it with the Arena simulation model results.Finally, a continuous container berth group in north China is taken into example, the correctness of the calculation results of queuing model for different range of capacity is verified. Besides, when twin 40 feet quay cranes and normal quay cranes are mixed used, the optimal configuration numbers or allocation strategies of quay cranes for minimum port operation costs are given out. The results show, when the container berth groups of twin 40 feet berth and normal berth are (0,5), (1,4), (2,3), (3,2), (4.1) and (5,0), the optimal configuration of twin 40 feet quay cranes and normal quay crane are (0,35), (6,28), (10,21), (15,14), (20,7) and (25,0), respectively.