Study On Random Vibration Of Railway Track And Reliebility Of Concrete Sleeper Ⅲ

Based on the thought of interaction between vehicle and track, the spatial coupled vehicle/track vibration model was built for high speed railway track, and applied in the track irregularity, which was treated as a stationary ergodicity process. The random vibration laws of railway track were investgated. Further more, the random vibration laws were studied by using Monte Carlo random FEM (finite element method) under the condition that the track parameters of fastener stiffness and ballast stiffness are treated as random parameters obeying normal distribution. The reliability of reinforced sleeperⅢwhich will be used in high-speed railway in China was investgated.Main contribution and achievement in this thesis are listed below:1. The model of spatial coupled vehicle/track system was established for high speed railway. In the model, track irregularity movement was used instead of train movement, rail was modeled as Euler beam element, sleeper and ballast was modeled as gird body element, the boundary was modeled as half-infinite beam element, and Hertz nonlinear contact was applied between wheel and rail.2. The new concept of artificial short wave of track irregularity was put forward, and a sample of artificial short wave was built. In combined of the sample of short wave and the sample of low disturbance track irregularity of high speed railway in German, a simulated sample of random track irregularity was established to study the vibration laws of track in high speed railway.3. The vibration of vehicle/track system was calculated under the excitations of random track irregularity, and the results were statistically analyzed. The effect of train speed on vibration was very large.The results showed that probability distribution of the acceleration of rail, sleeper and ballast, and the force on sleeper obeyed normal distribution. As train speed increases from 160km/h to 350km/h, the vibration responses of vehicle and track (which involve acceleration, contact force between wheel/rail, the force on sleeper, the stress on subgrade, and the displacement of rail, sleeper and ballast) were all increased but in a relatively different manner. The values of acceleration increase were the highest. The values of contact force between wheel/rail, force on sleeper and stress on subgrade were relatively low. The values of displacement increase were the lowest.When train speed increases from 250km/h to 350km/h, the value of vibration responses had a recognized increase, acceleration of rail increses from 158g to 581g, contact force of wheel/rail increases from 280kN to 350kN, and press force on sleepers increases from 92kN to 109kN,. The increase in value of acceleration was the highest, the value of acceleration of wheelset and rail may be doubled or even more. 4. Samples of fastener and ballast stiffnesses were established, because the variation range of fastener and ballast stiffnesses are wide and fastener and ballast stiffnesses are very sensitive, and the fastener and ballast stiffnesses were treat as random parameters that obey normal distribution through out this work.5. A sample of random parameter of fastener and ballast stiffnesses and a sample of low disturbance track irregularity of high-speed railway in German were combined as excitation, the random vibration was investigated by simulation calculation, and the results were statistically analyzed.(1) The range of extreme values of rail acceleration, sleeper acceleration, ballast acceleration, wheel/rail force, force on sleeper and stress on subgrade were very wide, but the range of extreme values of rail acceleration were the widest.(2) Probability distribution of the extreme values of vehicle/track vibration responses obeyed extreme value I distribution checked byχ2 condition in the signifycance level of 0.05.(3) When the train speed increases, the random vibration responses will increase same as the trend in point 3 above, but the values in comparing with it were much higher. It means that the dynamic responses of high speed railway are very significant, and more attention should be payed to it.(4) The parameters of high speed railway track structure (especially fastener and ballast stiffnesses) had much more impact to random vibration responses of vehicle/track system, so they should be optimized and remained in a narrow range.(5) The dynamic coefficients of design wheel load in all speed classes in China by studying the calculation results of wheel/rail forces were put forward. When train speed are 160,200,250,300,350km/h, the adviced coefficients of design wheel load in China are 2.4, 2.8,3.0,3.5,3.7.6. Four failure modes of concrete sleeperⅢwere established and influence factors of resistance and loading effects of them were analyzed, including concrete cracking and crush failures (because of fatigue bending moment in sleeper section) under rail and in the middle of sleeper section.7. Based on the real work conditions of concrete sleeperⅢ, a model of sleeper support was build and used to analyze the Concrete sleeperⅢ. In this model, there is a uniform distributed reaction force q1, as well as a pair of revised trapezoidal distributed reaction force which are symmetrical about the sleeper section under the rail, their height are (q2-g1), and their top and bottom edge width are (2l1+l2) and l2 correspondingly. Using the modle, the loading effects of concrete sleeperⅢwere solved.8. The calculation method to solve sleeper section resistance used static cracking test load, which was established to calculate the fatigue bending moment and the fatigue compressive stress on the edge of compressive concrete. 9. The distributions of loading effects, and resistance were given, also the statistical parameters and distribution functions were given. The distribution of loading effects obeyed extreme value I distribution, but the distribution of resistance obeyed lognormal distribution.10. Failure probability and reliability index were calculated by JC method. The reliability index and failure probability in case of the resistance reduction and loading effects development factors, were neglected, were 3.583 and 0.017% respectively, but in case they were considered the results were 2.909 and 0.18% respectively. For the concrete sleeperⅢ, both of the failures probability are acceptable.11. The above research results showed that the concrete sleeperⅢcan be used in high speed railway in China.