Cascading Failure Modeling And Vulnerability Analysis Of Logistics Infrastructure System

Urban lifeline system contains infrastructure systems provide service including power,water,gas,telecommunication,traffic and so on,which is of necessity for the operation of urban function.The networked and interdependent infrastructure systems have improved operation efficiency as well as service quality to a large degree,but brought disadvantageous influence to system safety under complex environment.The local and tiny disturbances on infrastructure caused by random failures,natural disaster and deliberate attacks may spread to other parts of the network due to functional interdependency among the different components.Interdependency may cause failure spreading among different systems iteratively,thus augments the final failure scale.Phenomenon of the local failure on network spread to the other parts based on functional relationship was called cascading failure,and failure on a small portion of critical components can even cause a large scale of paralysis on network,which poses a great threat to financial and social activities.In view of the lack of research of cascading failure with respect to logistics infrastructure system based on interdependent network theory,the logistics infrastructure system was then abstracted into an interdependent network consists of task assignment network and traffic network based on their interdependency in structure as well as in function.The failure mechanism was constructed based on load-capacity model and user equilibrium traffic flow assignment,and network load,capacity,load redistribution mechanism as well as functional relations between the networks were also constructed.The vulnerability of the interdependent network was analyzed from the perspective of cascading failure,and the importance of the infrastructure nodes was also assessed.Based on a kind of tunable task load redistribution model,random failure and deliberate attack were respectively simulated by removing a specific proportion of nodes randomly or deliberately,the loss degree of task load and traffic efficiency were used to assess damage to the interdependent system.The influence of topology of task assignment network,coupling strategies as well as strength of the networks,homogeneity of load distribution,capacity extension strategy,load redistribution mechanism and node failure mode to the vulnerability of the logistics interdependent network were analyzed.Suggestions of vulnerability reduction subjected to the conclusion stated were also given.The double-layer flow equilibrium model of the interdependent network based on path choice mechanism as well as the related cascading failure model was used to analyze node importance.Based on the thought where the importance of node is equivalent to destructive effect,node importance with different failure modes as well as different assessment methods was calculated and analyzed in the perspective of destructiveness to the network after node failure.Results among different methods proved the effectiveness of the proposed method,those among different node failure modes revealed the influence of network dynamics such as load distribution in node importance.Thus detailed grasp of interconnected network flow as well as node failure mode ensures the reliability of node importance investigation.