Risk Assessment Of High-speed Railway Overpass

With the increasing volume of high-speed rail transportation,the number of new bridge construction projects crossing existing high-speed railway lines is also increasing.There are many sources of risk in the construction of newly constructed cross-line bridges,and the resulting risk events often occur.Establish an effective risk analysis method to determine the various risks that may occur during the construction of the high-span high-speed railway bridge,which can assist the design and construction units to fully understand and control the construction risks.Reduce the risk level by formulating corresponding preventive measures to ensure the safety of the new bridge during construction and prevent the risk factors from causing serious casualties and property losses.Therefore,the risk analysis and evaluation of the construction process of the high-span high-speed railway bridge are of great engineering significance to ensure the safety of the construction process of the new bridge and the normal operation of the high-speed railway below.The current risk assessment methods are still imperfect.For example,most risk assessments are based on expert opinion for qualitative judgments.There are few studies on quantitative analysis,and there are often subjective factors in the assessment process,which cannot accurately reflect the real situation.In this paper,by arranging the research results of risk assessment in the construction process of bridges at home and abroad,the quantitative calculation methods and procedures of risk probability are established to solve the problems that the quantitative calculation of risks in the whole process of the construction of high-span high-speed railway bridges is less.The main research content and results of this article include the following six parts:(1)Define the construction risk of the upper-span high-speed railway bridge,summarize the typical risk scenarios of the construction process of the upper-span high-speed railway overpass and the risk sources of different construction methods through the accident summary;give the bridge risk assessment system.(2)Combined with statistical inversion theory,a quantitative analysis method suitable for a type of risk situation that can be expressed and expressed by the limit state equation is established,and the limit state equation of three different construction methods in the typical risk scenario during the construction process is determined.(3)As an example of the construction process of the above-span bridge swivel,the construction risk probability estimation was focused on the risk scenarios of sphericalhinge rotation instability in the longitudinal and transverse directions under wind load and unbalanced weight.The probability of bridge risk is higher than that of longitudinal bridge,which verifies the feasibility of this method.(4)The above cantilever construction process of the bridge is taken as an example.On the basis of the risk probability estimation of the maximum cantilever construction stage,the risk evolution estimation is completed,that is,the calculation of the risk probability with the construction stage and the conditional risk probability are considered.According to the parameter sensitivity analysis,it is found that the resistance of temporary anchoring has the greatest impact on the structural stability,followed by the deviation of the self-weight on both sides of the cantilever.(5)The above-mentioned cross-bridge thrusting construction process is taken as an example to estimate the risk probability of cross-section compressive stress overrun during the entire thrusting process.On this basis,the inversion theory is combined with the monitoring information in the construction process to complete the load parameters And the dynamic update of the risk probability,the posterior distribution of the risk factors of the real bridge project is calculated.The standard value of the axial compressive strength of concrete and the number of prestressed bars obtained from the parameter sensitivity analysis have a great influence on the risk of cross-section stress overrun.(6)After completing the quantitative calculation of the overturning risk of the two construction methods of swivel construction and cantilever construction,a comparative analysis shows that the risk level of ball hinge instability during the swivel construction process is higher than that of cantilever construction.