Risk Assessment Of The Construction Phase Of Large Span Bridge

With the development of national economy and technology, a large number of modern cable-stayed bridge sprang up, they bring more convenient trips, but also make the city more beautiful. The development of modern cable-stayed bridge has experienced from small span to long span, due to the increase of the span, it brings even more complexities, also leads to uncertainty within the process of construction, these uncertain factors would make the cable-stayed bridge face much unknown risk, it is necessary to take active measures in case of risks in the construction process of the cable-stayed bridge. This paper baesd on the cable-stayed bridge which stride over the HuangShui river, in XiNing, QingHai province, considers of the practical construction, it do some evaluation research for the risks of long-span cable-stayed bridge in construction stages.First of all, the development of cable-stayed bridge, the domestic and foreigner search tendency, and some problems in the development of cable-stayed bridge are listed, then this paper introduces the basic theory of bridge risk assessment and the method of risk factors identification on bridge, all above lay a foundation for the identification of risk factors during construction of the cable-stayed bridge, it is convenient for risk assessment work. The simulation model of TongHai bridge is built in midas Civil, the bridge, the tower the guy, and the pier are simulated, it could identify the risk factors in the level of structure. Using expert investigation method and Delphi method, all risk factors will be identified. Then the weight calculation could be analyzed with hierarchy process for TongHai bridge. According to the grey number in five kinds of gray classifications of safe construction, the score can obtain in second class indicators with the expert model, all that compose the table of evaluation which considers the risk factors, with calculation of explicit weigh function and weighting factor, the factor of clustering coefficient can classify the level of the bridge, such this, the risk evaluation of the bridge in construction stages is completed.The results indicate that in the construction stages of cable-stayed bridge, the tower is easy to be risk firstly, the cables secondly, the girder, the piers are after ranked. In the construction stages of cable-stayed bridge, in terms of cable tower to control risk, the most important factors are density of material, cable forces, working load, wind load, the sectional dimension, concrete shrinkage and creep, the temperature the support subsides, performance of the machinery and accidental damage of cables are important either. In terms of girder to control risk, it mainly focus on density of material, cable forces, the change of temperature, working load, wind load and the height measurement of the girder. In terms of cable to control risk, it contains the cable forces, the temperature of cables, wind load and stress relaxation. In terms of bridge pier to control risk, the important are support subsides, the working load, the change of temperature and the concrete shrinkage and creep.