Study On Risk Analysis Method Of Long-span Bridges During Construction

Combined with recent research progresses of engineering risk Assessment, structural analysis of bridge construction, structural reliability analysis, the risk theory and the risk method on the bridge engineering during construction are studied in this thesis for the application and the scientific research. The main efforts are devoted to those items as below:1. Due to the characteristic of ordinal consistency in the analytical hierarchy process (AHP) diffcult to meet, the method Combined AHP and the theory of fuzzy mathematics is introduced, the idea of fuzzy analytic hierarchy process is introduced innovatively. The failure mode and the main factor of failure induced during construction of bridge engineering are identified. The method can exert the brain advantage of evaluation, and simplify the computation process.2. Because Random walks can't give attention to the quality and quantity of the samples set, the uniform design method is used in risk Assessment during construction of bridge engineering. The samples set can satify needs of compact property,ergodic property and consistent property, and which is simple and practical.3. In order to acquire the explicit performance function of complex structure, the method of implicit expression to explicit expression is introduced. Examples show that the method is very accurate and practicable.4. In order to carry out the calculation of risk quantification, the UD-FEM-NN-SORM method of risk probability computation is putting forward. The artificial intelligence technic can apply to risk probability estimation, which will avoid the precion problem of response surface methodology and the deficiency of random simulation with heavy computation. Risk probability estimation will be more accurate and practicable.5. Risk loss is studied. The failure loss mathematical model is established to show the content and the magnitude of risk consequence.6. The principle of balance between economy, technology and safety is studied. According as the principle, the risk assessment is presented to estimate the risk during construction reasonably.7. The software BRE2006 for bridge engineering risk assessment during construction is built, using Matlab. This system has Friendly interface and easy operation, and has both the quantitative and semi-quatitative method of bridge engineering risk assessment. The software is very pratical and very flexible. 8. A synthetically risk assessment for YiWuJian Bridge and JiaShao River-Crossing Bridge is presented. In which the risk assessment method and the software are verified practically and availably. This study lays a solid foundation for the method and the software spread widely in the risk assessment field of bridge engineering during construction.