Research On Safety Risk Assessmentof Construction For Urban Elevated Road

With the accelerating process of urbanization, traffic congestion has become a"bottleneck" which restricts the urban development. In order to improve the existing traffic conditions effectively, most large and medium-sized cities at home and abroad have a plan to construct urban elevated road system. Urban elevated road cuts through the central region of the city with "banding shape" or "ring shape",which is crossing the existing municipal roads and bridge system. The underground pipe network and municipal facilities are covered densely in construction region. It is necessary to ensure the safety of urban operation and the construction of elevated road.Construction safety risk is high and the risk source is extensive and comprehensive, both the construction safety technology and the management factors, and the personnel equipment factors, traffic environment and the natural environment factors. Safety accident has the characteristic of frequent and easy occurring .It is difficult to manage and control the safety risk. Therefore, how to carry out the safety risk assessment of the city viaduct scientifically, improve the construction safety level of risk control, prevent the construction safety accident effectively, has become an important topic of this kind of project to solve. In this paper, the main research work of the urban viaduct construction safety risk assessment is as follows:After a review of project construction safety management of the national large elevated road, reference materials, statistical analysis date of bridge construction accidents,summarize the security risk characteristics, the cause of accidents, and accidents law of urban elevated road construction. Accident-caused mechanism is analyzed based on fault tree theory which include the collapse, falls, object strike, causing injury due to mechanical mechanisms, electric shock etc.. The three dimensional safety risk identification method is proposed based on the WSR System Approach, and the risk transmission mechanism also is analyzed, which have laid a theoretical foundation for the risk assessment of later.Analysis ofthe connotation of hazards and hidden dangers of accidents, the urban elevated construction safety accident risk factors are analyzed from the aspects of construction operation and construction environment, and the identification method and basic procedure of urban elevated road construction hazard is proposed. The key parameters and evaluation standard of the methods for the analysis of the work condition risk is improved, introducing risk correction factor, and hazard evaluation model of urban elevated road constriction is established. Evaluate the real risk state of the hazard source dynamically,which provides the basis for the process safety risk assessment.The index system of process risk evaluation is established on the basis of the analysis of construction safety accident risk formation mechanism of the key technology, such as the urban elevated road foundation construction, high pier construction, beam and plate hoisting construction and cast-in-situ construction. Based on the Kent index method, the safety risk assessment model of urban elevated road construction technology was established. The quantitative evaluation and analysis on the safety risk of the construction process of the urban elevated road is implemented.the probability of risk events is transformed into the probability index by model, which overcomes the shortcomings of the risk assessment index sample with small size and dynamic performance and the difficulty of obtaining the accurate probability.On the analysis of legal relationship, legal responsibility and influence mechanism among the owners, construction, supervision, design and other projects of the urban elevated road project, in the form of questionnaire, the influence factors of construction safety related to the subject behavior factors were investigated and analyzed.The attribute reduction model of risk factors is set up based on the rough set theory, the importance of group behavior risk factor is analyzed and screened, the key risk factors of influencing the construction safety is obtained, and the risk evaluation index system of related party group behavior is established. Considering the interaction of the owner, construction, supervision,design and other related parties of the urban elevated road project, and has the uncertainty and fuzziness, the risk assessment model of the related party’s subject behavior in the construction of the elevated road project is established and the empirical study is carried out based on matter element theory. The model fully reflects the dynamic nature, contradiction and fuzziness of stakeholders’ behavior,which reflects the mutual influence and interaction of the evaluation objects.Taking the project of Second Ring Elevated Road in Chengdu city as a case, an empirical analysis is made on the hazard source,construction technology and related party’s behavior of the urban elevated road construction. The feasibility and the scientific nature of hazard source, construction technology and the safety risk assessment method of related party’s subject behavior were verified.The safety risk coping strategies of the urban elevated road construction is discussed from four aspects of the risk avoidance, risk transfer, risk mitigation and risk retention in this paper. The game model of the related party safety management is established and the countermeasures of safety risk control are put forward from the angle of the owner. On the project stakeholders to participate in the safety management attitude and enthusiasm, as well as the correlation of safety penalties, safety culture construction, safety supervision and other measures of the owners were discussed. The safety risk management information system of the urban elevated road is built based on the Internet and modern information technologyto carry out dynamic management and timely monitoring of risk.