Research On Fatigue Life Analysis Method Of RC Bridge Deck Under Random Taffic Loads

With the rapid and steady growth of China’s economy, the traffic capacity of the road in China has been increasing rapidly, the problem of overloading has become more and more serious, which leads to a large number of fatigue problems in the highway concrete bridges under the action of vehicle load. Before the bridge structure design, designers tend to attach importance to the overall structure of the bearing capacity, mostly to carrying capacity as the main indicators of the bridge structure safety control. But in the current situation, bear local vehicle load effect of bridge component is likely to lead to fatigue damage, thus affecting the overall bridge structure performance. Therefore, in this paper, the fatigue life of concrete bridge deck is studied by the method of analysis of fatigue life of concrete bridge deck under random vehicle load.First of all, this paper makes an investigation on the traffic volume of a certain highway, and summarizes the vehicle type on the highway, and establishes the typical vehicle load bank. The main parameters of the traffic volume statistics, such as the proportion of each vehicle type, vehicle spacing and vehicle axle load distribution, etc. made subject analysis to determine the main parameters of the probability density distribution, lay the foundation for the subsequent generation of random traffic. The equations of motion of a typical vehicle are constructed by using the Lagrange principle. Often in the selection of highway simply-supported continuous fabricated prestressed concrete T beam bridge, the ANSYS finite element model is established and modal analysis. Using modal synthesis method of vehicle bridge interaction equation is established, the matlab program is compiled to calculate and analyze the parameters. Analysis of the different types of vehicles, different speeds and different deck uneven impact effect of flatness under vehicle load on the bridge structure, and calculation results of specification, provides the reference for the engineering application.Then, this paper discusses the mechanism of fatigue damage of reinforced concrete, and points out the main factors that control the fatigue failure of the bridge deck, and puts forward the method of damage mechanics to study the fatigue life of bridge deck. Under the effect of random vehicle, bridge panel of stress time history is calculated by using MATLAB vehicle bridge coupling vibration program, using the rain flow counting method to get stress amplitude and the mean stress, plug in the fatigue life prediction model based on damage mechanics of the fatigue life of bridge panel. At the same time, considering the factors such as traffic volume growth and the deterioration of bridge deck, the variation law of fatigue life of bridge deck is analyzed.Finally, the analysis of the domestic major highway overload situation points out that the vehicle type overload ratio and overload rate. Simulation with random traffic overloading of vehicles, the change law of the stress amplitude of the bridge under the action of the vehicle is analyzed. In the early and middle period of the service life of the bridge structure, the effect of the random traffic flow on the bridge deck is discussed.