Research On The Dynamics Evolution Model Of Urban Disaster Chain And The Risk Assessment Method Of Disaster Chain

Abstract:As the urbanization process is accelerating, the chain effect of urban disaster becomes more and more obvious, and the loss caused by the disaster chain effect is bigger and bigger. Therefore the urban disaster risk assessment must put the disaster chain as a core, it is possible to comprehensively and systematically grasp the hazard degree of urban disasters. Then the assessment can provide reliable theoretical basis for building regional integrated prevention and mitigation disaster system, and urban disaster risk management. The thesis focuses on some key technology of the city disaster chain and risk assessment, and the main effects are as follows:(1) The formation mechanism of urban disaster chain is analyzed, and the result shows that the complex interaction relation of the disaster carrying bodies is the immediate cause of disaster chain effect. The analysis for chain effect of four kinds of typical urban disaster shows that the urban disaster chain has complex network structure characteristics. The energy effect of the city disaster chain indicates that the coupling effect of the excitation energy releasing from disaster-inducing factors and the energy of the disaster carrying bodies is the root cause of the disaster chain.(2) The evolution regulation of urban disaster chain is analyzed. The result shows the urban disaster chain has periodic inoculation characteristics, and there are continuous influence behavior and instantaneity influence behavior, two different behaviors in time effect. Based on the evolution rule of disaster chain, the mathematical model of disaster chain is established to describe the disaster loss rate and the degree of disaster loss of various disaster nodes. And the model to cut off disaster chains and mitigate disaster is put forward based on the vulnerability of disaster nodes and the connection sides.(3) On the basis of description of the dynamic mechanism of urban disaster chain system, the disaster scene is set at first, considering the influence of time lag, then the system dynamics model of urban disaster chain and urban disaster management is established. With Vensim, the simulation analysis software, the evolution process of urban disaster chain system is analyzed, the effect relation has been gotten between the vulnerability of part of disaster carrying bodies and disaster loss rate, and it is pointed out that the most effective method of reducing personnel casualties in the urban disaster is to reduce the vulnerability of urban lifeline. The system dynamics model of urban disaster management shows that there is the interference and supplement relationship between disasters and economic, and to emphasis on spillover effects of the disaster management system can improve the effectiveness of reduction disaster system.(4) The disaster loss sensitivity evaluation models of the main disaster carrying bodies such as population, urban buildings and lifeline have been respectively established. The body’s endurance and emergency self-help ability characterization are respectively used to characterize the disaster loss sensitivity of gradual disasters and suddenness disasters. The index of the building structure and the index of use of time are used to characterize the disaster loss sensitivity of building. Using the theory of equilibrium entropy and brittle entropy the vulnerability of single function network and the subsystem brittleness association degree are characterized, lifeline system damage sensitivity evaluation model is established, then the disaster loss sensitivity evaluation models of the lifeline is established.(5) From two aspects of fundamental disaster emergency ability and special disaster emergency ability, the multi-level index system of urban disaster emergency ability evaluation is established. On the basis of quantifiable change for the index system, the weight coefficient of each index is determined with the improved hierarchy analytic method. Considering fuzzy and hierarchy of the evaluation index system of the urban disaster emergency ability, the fuzzy comprehensive evaluation based on fuzzy pattern recognition is established. The optimal membership degree of each index is constructed so that the evaluation of urban disaster emergency ability is more scientific and accurate.(6) Based on the analysis of multi-risk assessment methods and risk assessment methods of supply chain, then the joint probability distribution of disaster loss grade of every node is obtained using Bayesian formula. And the risk assessment model of urban disaster chain is constructed. Considering the differences between disaster chains caused by technology disasters and natural disaster chains, the risk assessment model of urban technology disaster chains is set up taking the domino effect as the core. And the application examples show that the model established has higher consistency with actual situation, this also explains the model is practicability.