Research On Risk Assessment And Prevention In The Initial Design Stage Of Super Large Bridge

With the rapid development of the times,bridge engineering is facing many problems,such as increasing technical requirements,increasing construction intensity,and more and more complex operations management.Therefore,bridge engineering must explore more effective risk assessment methods.Based on the LEC method,this paper introduces the failure tree theory and reliability index,and combines the grey situation decision method to carry out risk assessment in the preliminary design stage of the bridge according to the engineering characteristics.Firstly,the paper summarizes the current situation of risk assessment in construction stage and design stage at home and abroad,and introduces the concept,method and workflow of risk assessment.Secondly,taking a bridge in the small Three Gorges of Danjiangkou as the research object,the engineering data are collected,and the risk screening of the design scheme is carried out by using the expert investigation method.The weight is set according to the expert investigation method,and the best scheme is selected.Furthermore,the quantitative assignment standard of L value(the possibility of risk accident)in LEC method is optimized by combining the failure tree theory and the reliability index to improve the value accuracy of risk probability.According to the engineering characteristics and project requirements,the quantitative assignment category of C value(consequences of dangerous accidents)in LEC method is refined,the consideration scope of risk consequences is expanded,and the risk value is calculated according to the LEC method formula.Finally,the grey situation decision-making method is used to compare the preventive measures for high-level risks,and corresponding preventive suggestions are put forward for low-level risks.On the basis of theoretical research,this paper introduces specific cases,applies theoretical research to practical cases,and verifies the feasibility of the theory.By improving the LEC method and combining the grey situation decision-making method to assist in formulating preventive measures,the shortcomings of the traditional semi-quantitative and semi-qualitative risk assessment method are solved to a certain extent.The improved LEC-grey situation decision method is used for the comparison of risk assessment and preventive measures.This method is more accurate in the assessment of risk factors and more targeted in the selection of preventive measures.