| With the comprehensive promotion of economic globalization,international trade has become increasingly frequent.The volume of cargo continues to grow,and the accompanying port congestion problem has become more and more serious.Especially in 2020,due to the large-scale outbreak of novel coronavirus pneumonia epidemic around the world,many ports have experienced large congestion,which has aroused strong concern in the market and shipping industry.If port congestion cannot be dealt with in time,it may even stall the entire shipping network,affect the normal operations of shipping companies,and cause huge economic losses.Under the background of port congestion,the paper reviews and summarizes the relevant literature to illustrate the shortcomings of the current research,combining the actual needs of the shipping company,considering the different operating strategies to design the hub-and-spoke shipping network,and provide some reference for shipping companies’route operation.Firstly,the paper analyzes the relationship between congestion cost,waiting time and cargo flow.By analogy to the related theories of road traffic congestion,the BPR road resistance function is introduced and appropriately deformed to obtain the time characteristics of port congestion and the expression of cargo flow.Based on the expression of the port congestion time and cargo flow,the congestion cost will increase exponentially with the increase of cargo flow,and then establish congestion cost function of hub port to quantify congestion cost.Secondly,from the perspective of shipping companies,this paper explores the objectives of cost control strategy and congestion control strategy.Based on the assumption of container transportation and hub-and-spoke network structure,the hub and spoke shipping network mathematical model considering hub port congestion under different strategies is constructed.Because the mathematical model belongs to the non-linear integer programming model,it is difficult to solve it accurately.So genetic algorithm is designed to solve the model.By debugging the experiment,the operator value of genetic algorithm is determined by comparing the experimental results for many times.Finally,a calculation example based on actual route data is substituted for calculation experiment.The network cost and hub port location configuration schemes of cost control strategy and congestion control strategy under different parameters are obtained,by carry out sensitivity analysis of the solution results and put forward relevant suggestions.It is indicated that in daily operation,shipping companies need to consider ports capacity,formulate congestion cost quantitative model,predict congestion effect of network,and timely change operational strategy,so as to effectively avoid potential risks. |
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