| At this stage,urban renewal with urban stock development as the main means has become an important way to improve urban living environment,improve urban infrastructure,and promote urban economic growth.Due to the diverse demands on urban functions in the new era,the types,scales,processes and participants of urban renewal are becoming more complex,and there are many large clusters of projects with complex renewal processes.If risks occur in such projects during the renewal process,it is likely to trigger a butterfly effect and develop into a global risk,causing huge losses.Therefore,studying the risk types and contagion characteristics of urban renewal large-scale engineering projects,reducing the occurrence of risk events at the source,and ensuring the smooth operation of urban renewal engineering project clusters is a current issue that needs to be addressed urgently.This study takes the urban renewal project group of Qinglongsi area of Xi’an City(hereinafter referred to as the urban renewal project group of Qinglongsi area)as the research object,and the risk contagion characteristics of the construction process of Qinglongsi area renewal project group are studied through a combination of static analysis of complex networks and dynamic simulation of risk evolution,Firstly,sort out the relevant concepts and clarify the risk transmission mechanism of the project group;secondly,explore the construction sequence and the risks in the construction process of the Qinglongsi area renewal project group,use the complex network theory to construct the risk contagion network during the construction period of the urban renewal project group,and analyze the network characteristics;Finally,the fuzzy cognitive map theory is used to simulate and dynamically simulate the risk changes in the renewal process,analyze the internal laws of risk contagion,and then propose scientific risk prevention and response strategies.The main research results are as follows:(1)Revealed the risk contagion mechanism during the construction period of urban renewal project group.The risk contagion mechanism of urban renewal projects was charified by the concepts of emergence and fragility,and the structure of the contagion network was studied.The risk contagion network of the project cluster is a 2-tier interdependent network composed of the risk logic layer and the sub-project layer,which mainly has two forms of infection,one is that the risk occurs and triggers other related risks through intra-layer contagion,and the other is that inter-layer contagion leads to the collapse of the sub-project under construction,which in turn prevents subsequent sub-projects from proceeding smoothly.The contagion mechanism of programme risks helps to clarify the internal logic of project risks,so as to help guide the prevention and control of programme risks.(2)Researched and constructed the risk contagion network model of Qinglong Temple renewal project group during construction period.The risk contagion network consists of 7 sub-project structure nodes,20 risk logic nodes and 304 edges.The network characteristic analysis results show that the demolition of existing buildings in the renewal project group of Qinglong Temple area is the most important stage for risk prevention and control.The government support is insufficient,the historical and cultural environment is destroyed,and the risks of coordination among related parties are highly contagious.Focus on prevention,social stability risks,related party coordination risks,and budget overrun risks are highly contagious and require focused monitoring.The demolition of existing buildings,new housing,and housing renovation are the update stages where risk contagion is most likely to occur.The main form of risk contagion at this stage is demolition coordination risk→related party coordination risk→social stability risk.The above features have good effect on project cluster risk avoidance.(3)A simulation model for risk contagion evolution of engineering project groups based on fuzzy cognitive graph theory was constructed.Simulation of the change of risk state values during the construction of the Qinglongsi area renewal project group,and derived the risk dynamic change law of the project cluster during the construction period.Combined with the simulation results,four core risk indicators were screened,different risk scenarios were set,and the internal laws of risk contagion under various scenarios were obtained through evolutionary simulation.The results show that the core risks mainly increase the overall risk of the project by blocking the smooth progress of the project,increasing the project budget,triggering design changes,and hindering the coordination of relevant parties.Among them,the lack of government support has the most significant effect on other risks,and the system state is the most unstable when the government’s support for the Qinglongsi area renewal project is insufficient,which is easy to cause other risks. |
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