Fatigue Reliability Analysis Of Cable-stayed Bridge

With good performance of mechanism, the cable-stayed bridge is one of the most widely used types of bridge structure nowadays. With the rapid growth of traffic vehicles and the circumstances that many large-span cable-stayed bridge often to be situated in windy strip, the problem of vibration response under the loads of wind and vehicles is prominent. And the frequent changed loads will cause cycle stress and structures fatigue failure.Based on previous work on load spectrum theory, bridge fatigue theory and reliability theory, this dissertation proposes stress peak-to-peak value correction coefficient and cycle of stress frequency correction coefficient method, which agrees with the real situation more accurate than the previous results. On the basis of theoretical simulation of vehicle load and wind load, specialized procedure BDANS has been carried on time-domain analysis and fatigue reliability analysis of the Hangzhou bay bridge.Firstly, with considering the wind influence, statistical analysis of the vehicles load and the wind load is carried on and the stochastic stream of vehicles load spectrum is obtained accordingly. In addition, the discussion on the mechanism of the coupling of wind and bridge is also considered.On the foundation of the Miner linearized cumulative damage theory and fatigue reliability computation and with considering each circulation stress influence, this dissertation proposes the computation idea that considers the interaction of circulation stress. In addition, the dissertation also introduces the stress peak-to-peak value correction coefficient and the cycle of stress frequency correction coefficient for the first time, and obtained a new fatigue life computation formula.With the specialized procedure BDANS design by the research organization of Dr. Han Wan Shui, the acceleration, the displacement, the stress time interval curve are obtained, respectively, under the various conditions of Hangzhou bay bridge. By analysis ,the short cables receive more fatigue circulation stress ,but it support much smaller stress peak-to-peak value than the long cables. Finally ,the fatigue reliability of short cables has been improved .So ,it is concluded that the stress peak-to-peak is hardly effected the fatigue failure .When the wind speed under 40m/s ,the mid-span Moment limit value is 4 to 5 times of when it under 20m/s ,and the Moment limit value is very big .So ,the wind is the most influentia factor to fatigue reliability analysis. Finally, the worth attention of weary fatigue reliability research aspects and the direction in this area are pointed out, respectively.