Research On Transportation Network Of CHINA RAILWAY EXPRESS Based On Hub-and-spoke Theory

With the continuous advancement of the " The Belt and Road" initiative,the economic and trade exchanges between the countries along the route are getting closer and closer.The China Railway Express has played a vital role in supporting the circulation of goods by overland transportation between China and Europe.The China Railway Express,as a carrier of China-Europe trade,are ushered in a period of vigorous development.The China Railway Express,an emerging freight product,has certain advantages in terms of transportation time and transportation costs.It has received increasing attention.Domestic and foreign cities have successively operating the trains.The number of routes and freight has increased rapidly,and the overall trend is positive,moving forward in High-quality development.As a product of international railway container transportation,the China Railway Express is a complex system engineering.This thesis mainly studies the construction of Hub-Spoke network for China Railway Express.First of all,the international railway intermodal transportation rules and channel conditions are sorted out in detail,and the current status of the China Railway Express is analyzed from three aspects: the number of China-Europe train service,major cities and areas,and customs ports.This thesis studies the characteristics of the transportation organization,puts forward the problems of point-to-point mode adopted by the China Railway Express,and the logical relationship between various aspects of the problem.On this basis,the key role of the the China Railway Express Hub-and-Spoke network in the "Trunk and branch combination,hub concentration" reorganization model was proposed.Secondly,the thesis analyzes the basic characteristics and advantages and disadvantages of the point-to-point network structure and the hub-and-spoke network structure,summarize the classic models and algorithms used in network planning.It is a theoretical basis for further research on the problem of the China Railway Express Hub-and-Spoke Network.Then,based on the single-distribution p-hub location problem,taking the cost and time characteristics of the China Railway Express into account,a bi-objective programming model considering transportation cost and transportation time is constructed.On the one hand,in order to scientifically express the scale economy and the discounts of transportation costs between hubs,a concave function of costs between hubs and flow between hubs is constructed,that is,a convex function of transportation discounts to flow between hubs.At the same time,a piecewise linearization method is used to approximate the function linearly.On the other hand,due to the agglomeration effect of the hub-and-spoke network,congestion at some hub nodes is unavoidable.In order to deal with the congestion problem reasonably,it is integrated into the transportation time target as a soft constraint,and the container arrival at the hub station is regarded as M/M/1 queuing model.In addition,the thesis uses the method of piecewise linearization and variable substitution to linearize the dwell time in the queuing model.In addition,considering that ports are the key nodes of international railway intermodal transport,it plays a vital role in the China Railway Express network.Therefore,a hub-and-port allocation model is constructed to solve the distribution relationship between hubs and ports.Furthermore,a Lagrangian relaxation heuristic algorithm is designed to solve the China Railway Express Hub-and-Spoke network model.On the one hand,the biobjective problem is converted into a single objective problem using the weighting method;on the other hand,the original problem is decomposed into two sub-problems according to the characteristic of the decision variables.Finally,for the constructed China Railway Express Hub-and-Spoke network model,the actual data of the China Railway Express are used to design examples to verify the validity and applicability of the model and method.It provides a certain reference for the transportation network planning under the "Trunk and branch combination,hub concentration " organization mode of the China Railway Express.