Study On Steel Box Girder Construction Safety Risk Evaluation And Control Of Long-span Cable-stayed Bridge Of Highway

As the increasing of investment in transportation infrastructure of China, the long span cable-stayed bridge because of its beautiful shape and novel structure form and many other advantages has developed by leaps and bounds in recent years. The steel box girder as a new type of main beam structure is widely used in long span cable-stayed bridge because of its light weight, high strength, big torsion stiffness and other advantages. However, as the increasing of span and innovation of structure of cable-stayed bridge, all kinds of safe risk questions is becoming more and more prominent in the construction process, it is mainly due to the steel box girder construction of long span cable-stayed bridge has a lot of security feature, such as large dimension, complex construction technology, the three-dimensional cross work and so on, meainwhile the affect by the natural climate, geology and hydrology and temperature change is obvious. But in the study of engineering practice at present stage, most is about the construction stress and alignment control, analysis and control of the security risk questions existed in the construction process of steel box girder are very weak. So how to identify, evaluate and control the construction safety risk of steel box girder of long span cable-stayed bridge in order to ensure the steel box girder construction can be completed safely and successfully, it has very important theoretical and practical significance.First of all, this paper focused on the situation about the steel box girder construction process of long span cable-stayed bridge has a lot of uncertain risk but its risk management and control is relatively weak, according to the characteristics of steel box girder construction, we identified comprehensively the possible safe risk of the steel box girder through factory production, transportation and hoist of each period, established the safety risk space of steel box girder of long span cable-stayed bridge and exhibit the factors of safety risk and its relationship intuitively by the influence diagram method; then this paper drawn into the idea of fuzzy mathematics based on most of the safety risk of steel box girder construction has the fuzzy uncertain feature, and according to the results of risk identification by influence diagram, established the fuzzy influence diagram evaluation model of steel box girder construction safety risk of long span cable-stayed bridge; thirdly, this paper established control system of steel box girder construction safety risk of long span cable-stayed bridge based on the risk identification and evaluation by the theory of risk control, also put forward the risk control measures of steel box girder construction contrapuntally; at last, this paper taken "the Second Yangtze River Bridge in Fengdu of Chongqing" project as an example, established the risk evaluation model of the project, and applied this model to evaluate the safety risk of steel box girder of the Second Yangtze River Bridge in Fengdu of Chongqing. According to risk factors of the model of fuzzy influence diagram are various and the large amount of calculation, this paper developed the computer evaluation system of steel box girder of long span cable-stayed bridge preliminarily, the system based on the theory of risk management as the overall design idea, completed the embryonic design about risk identification, risk fuzzy estimation and evaluation, it could help users manage the safety risk of steel box girder construction effectively.This paper is finished based on the scientific research project which is the Research of Construction Safety Risk Analysis and Control about the Second Yangtze River Bridge in Fengdu of Chongqing.