Study On Construction Risk Assessment Of Highway Railway Suspension Bridge

In recent years,with the continuous development of Chinese high-speed railways,a large number of bridges with large spans and new structures above the kilometer level have emerged,Especially,the suspension bridge is applied to the field of high-speed railway for the first time,which makes it face the challenges of less cases,strong risk concealment,complex quantity and changeable quantity.In order to reduce the risk during the construction of the suspension bridge for public and railway,and ensure the safety construction and construction quality of the bridge,it is necessary to carry out scientific and reasonable risk assessment research.This thesis relies on Wufengshan Yangtze River Bridge to carry out research on risk assessment of road-rail suspension bridge construction.The main research contents and results are as follows:(1)In the field of identification and evaluation of large-scale special bridge structure,a composite risk identification method based on WBS-RBS and expert surveys is proposed.Accurate and comprehensive identification of risk sources can be got through systematic risk identification matrix analysis and expert qualitative judgment.The risk evaluation is based on the risk source probability and loss grade results which obtained by the expert scoring method,then the fuzzy analytic hierarchy process and the risk matrix method are used to comprehensively evaluate the risk grade which from the whole to the part,and lays the foundation for the formulation of risk control countermeasures.(2)In view of the dynamic transmission characteristics of risk sources in construction,the risk meta-transmission theory is carried out to dynamic risk assessment,then the decisionmaking experiment and evaluation laboratory algorithm(DEMATEL)is adopted to simplify the relationship between risk elements and identify key risk elements to participate in the evaluation;And correlation analysis and causal reasoning methods are used to build a risk element transfer network.Moreover,taking Bayesian network theory to establish an evaluation model,the probability of risk element occurrence can be canculated,and key risk elements and main transfer chains are identified.(3)The evaluation process is shown in detail by Taking the Wufengshan Yangtze River Bridge as the supporting project and taking the large-volume cap of the north main tower as a specific implementation case,then the reliability of the proposed road-rail suspension bridge construction risk evaluation method is verified.The result of the risk identification of the whole bridge shows that: the whole bridge is decomposed into 10 sub-items and 78 basic construction procedures using WBS-RBS and expert survey method,and 744 risk sources are identified according to 35 risk decomposition items.(4)In the risk assessment results of Wufengshan Yangtze River Bridge: 131 high and above risk sources are assessed by improved risk matrix method.At the same time,168 major risk sources such as “uneven settlement of caisson foundation”,“excessive displacement of ground connecting wall-lined structure” and “uneven settlement of long and short piles” are assessed referring to fuzzy tomographic analysis method.Finally,according to the risk level results,the formulate specific technical plans,monitoring measures and other risk control countermeasures are used to control construction risks.(5)The results of Wufengshan Yangtze River bridge dynamic risk assessment show that234 dynamic risk elements,104 key risk elements and the main risk chains were identified in the whole bridge construction.After the completion of the construction,the risk probability value of the key risk element “high-speed railway driving safety” is calculated to be 0.0652,and the related key risk elements are: uneven settlement of caisson,linear deviation of main cable and so on.The main risk chain is: uneven settlement of caisson → anchor body change Position → Displacement of anchoring system → Deviation of main cable line shape →Uneven deformation of sling → Line shape change of main girder → Insufficient smoothness of railway bridge surface → High-speed railway driving safety.