Research On Optimization Of Empty Container Turnover In Rear Yard Of Export Refrigerated Containers

With the rapid development of the global economy and the improvement of living standards,people’s demand for fresh and refrigerated food is increasing year by year.Because of its advantages of high volume utilization,easy loading and unloading,relatively low transportation costs,and the ability to achieve "door-to-door" transportation,refrigerated containers have become the best means of transportation for refrigerated and frozen commodity trade.my country is an important exporter of fresh refrigerated food,and the throughput of refrigerated containers has increased year by year.Because the operation process of delivering empty refrigerated containers to the outboard trucks assigned to the shipper by the yard at the rear of the port is different from the process of delivering ordinary empty containers,an increase of "Pre-Trip Inspection" link,it is inevitable to turn over empty containers in the yard.Optimizing the scheduling management of the yard behind the reefer container and reducing the turnover rate of the yard are crucial to improving the operation efficiency of the yard.In the storage yard behind the refrigerated container,after receiving the information of the shipper’s reservation of the reefer container,the operator picks up the container and goes to the inspection area to refrigerate the container for inspection.When the container is picked up,the reserved(container number cannot be changed)and inspected reefer will be delivered.The above-mentioned operations for different shippers often overlap.During the yard operation,the choice of placement of the pre-inspected reefer containers when they are returned to the yard and the choice of the placement of the upper obstacle container when the target container is lifted will directly affect the amount of empty container turnover in the yard.This thesis first analyzes the reasons for the overturning of refrigerated containers in the rear yard,and determines the optimization idea based on the shipper’s scheduled pick-up information and the storage status of the yard.The top of the container is optimized for the placement of the container to reduce the number of turnovers in the yard.Then,according to the operation characteristics of the yard,with the goal of minimizing the sum of the cost of turning over the yard,the cost of picking and placing the container,the cost of moving the forklift and the delay cost of the external truck,the construction of the pre-inspected container entering and picking operation coordination The model is optimized,and a two-stage landing selection heuristic algorithm is designed considering the moving distance of the forklift.Finally,based on the actual operation situation of the yard,two types of cases are designed,which are two types of cases without pre-inspection completed container arrival and uninterrupted pre-inspection completed container arrival in the planning period.Compare and analyze the current operation methods of the yard.The results of the calculation example show that: when no pre-inspected containers enter the field during the planning period of the external collection card,compared with the KH and IH algorithms,the heuristic algorithm proposed in this thesis can calculate the number of container turnovers in a relatively short time.In the case of uninterrupted entry of pre-inspected containers during the planning period,compared with the current operation method of the yard,it is concluded that the algorithm in this thesis can effectively reduce the turnover rate of the yard,and with the With the expansion of the scale of the calculation example and the increase of the proportion of the approach container in the total operation container,the optimization effect of the container turning is more obvious.In conclusion,the two-stage placement selection heuristic algorithm proposed in this thesis can effectively reduce the turnover rate and the cost of carrying containers in the rear yard of refrigerated containers,and improve the operation efficiency and customer satisfaction of the yard.