The Fitting Methods Of P-S-N Curves And Prediction On Probabilistic Life For Stay Cable

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. Because bridge application materials science theory of development imperfect as well as vehicles overload, earthquake, wind and so on objective factor, some completed certain cable bridges has occured great span bridge appeared in such as the back guy corroded, the break, the king post crack and so on each kind of harm. These factors have affected the structure normal operation, even brought the secure aspect to the bridge the hidden danger. As the cable bridge primary member——stay cable life prediction appears very essential. The main contents are summarized as following:Firstly, when former stay cables computate fatigue life, they only uses50%probability-S-N curves to take the life estimate the foundation. In the actual project we hoped that the component has a higher probability, therefore this article utilizes the p-S-N curves to estimate under the different reliability the life of the stay cable. As the structure probability life foundation, this article summarized the domestic and foreign advanced p-S-N curves theoryies, namely with small samples, and fully, use data reasonably, withdraws more informations as far as possiblly from the limited empirical datum, we estimate the p-S-N curvesparameter accurately.Secondly, because of the limited primary data,we confirm the p-S-N curves experiment plan repeatedly to be whether reasonable. This article uses Monte Carlo method to have the random numbers, like this we may carry on experiments many times and confirms. At present each p-S-N curve theory is suitable for any concrete material or the numbers of small smaples, this mainly lies in the material of dispersivity and the numbers of small smaples. This point may be possible to see from each p-S-N curve theory and estimated value expression of life. Therefore this article uses three different dispersive materials to carry on the p-S-N curve experiment.Thirdly, as a result of the conventional fatigue test, the cycle of stress which exerts to the test sample usually is constant amplitude, but because the cable bridge gets a chill the load, the vehicles load and so on is variable amplitude. The signal that we obtain must transform into the constant cycle of stress finally, like this we can carry on the weary accumulation computation and the life prediction. Through the stay cable analysis, we choose the stay cable that was influenced greatly to carry on the analysis.We can obtain its stress time-history.Finally, this article summarized former the method of fatigue life prediction for stay cable. We analyze their feasible and the existence insufficiency. This article used different probability p-S-N curves to carry on the prediction of probability for stay cable.