| Since reform and opening up, our country has been in the rapid development period of traffic infrastructure construction. A lot of bridges need to be built, tied-arch bridge has been greatly favored in the bridge construction. Especially in recent years, our country has built a large number of long-span tied-arch bridge. However, there inevitably exist some security issues in the process of rapid construction. Whether suspenders work normally or not is related to the safety of the arc bridge which as important transmission components of tied-arch bridge. In recent years many bridge accidents which happened due to the suspenders failure and a large number of derrick replacement cases show that the reliability study of the suspenders is very urgent and necessary. This paper takes the Ying Zhou bridge as the research object, the suspenders fatigue reliability problem under traffic loads is studied on the basis of the existing relevant research results. The main research and achievements of this thesis are as follows:(1) The Ying Zhou bridge finite element model is established with ANSYS. According to the need of the fatigue analysis, some appropriate simplification of bridge structure is made in the modeling process. In order to validate the accuracy of the model, the data of modal test and suspender tension test is compared with the model calculated results. The results show that the simplified model can satisfy the precision requirement of fatigue analysis.(2) The Ying Zhou bridge load spectrum is got through the statistics of traffic flow of the bridge. The Monte Carlo method is adopted to establish the mathematical model of Ying Zhou bridge traffic, and the MATLAB software is used to program to realize the simulation of the traffic flow on the computer. Then the bridge load data of traffic flow can be got.(3) The simulated traffic flow is loaded on the finite element model of Ying Zhou bridge to calculate through program interface. The suspender stress-time history is exacted from results file and is counted with the rain flow method. Vertical suspender boom and inclined suspender are analyzed in the aspects of changes of stress, changes of stress amplitude and cyclic number. The analysis results show that the inclined suspender’s stress state is worse than vertical suspender’s. And on the same loading condition stress amplitude cyclic numbers are different with the position and arrangement way of the suspender.(4) Based on the cumulative damage theory, the suspender reliability calculation method is deduced which can be used in Ying Zhou bridge. After the required variables are obtained by adopting the method of simulation, the suspender reliability is calculated under the conditions with and without corrosion. Main conclusion as according to the results of the calculation: The reliability of inclined suspender index is lower than vertical suspender; The reliability index of the inclined suspender which is in the position of stiffness change, so this suspender is a danger suspender that need to be focused on; The reliability index of the suspender under corrosion situation has obvious decline than the suspender without corrosion, the declining rate of the reliability index increases with the extension of corrosion time.(5) This paper also gives another calculation method of the suspender’s fatigue reliability based on Weibull distribution probability theory, and the suspender’s reliability is calculated by using this method. The results show that this method can be used to the analysis of fatigue reliability of suspender as well. Although the results calculated with the method are more conservative, its calculation procedure is simple. So it is still a good analysis method. |
