| Synthesizing domestic and foreign existing tracks and the sleeper structures, comparing sleeper structures form at home and abroad appears that heavy haul sleeper form should be single block sleeper with shoulder on the ballast, using rubber mat under the sleeper to reinforcement if possible.Compare and analyze the dynamic load coefficient, the load distribution coefficient, support conditions under the sleeper, design bending moment and different calculation methods of bearing capacity of sleeper.Finite element method (FEM) is applied in simulating sleeper under different traction type, axle load, train running speed, the types of rail, the rail pad stiffness, sleeper spacing, the bearing stiffness under the sleeper and strength of concrete to get the sleeper’s mechanical characteristics. Within the scope of the working condition of each unit change, running speed is the most profound effect on the sleeper. Rail type and rail pad stiffness followed by. Sleeper spacing, the bearing stiffness under sleepers and strength of concrete is minimal. Suggest using electric traction, the highest speed of trains, the widest spacing between sleepers, the lightest weight of rail, the biggest stiffness of the rail pad and that under sleepers within the scope of the permit as boundary conditions in the sleeper design and calculation. Build vehicle-track vertical coupling dynamics model to calculate the load power spectral density and sleeper vertical acceleration power spectrum density in different train speed, the types of rail, rail, sleeper spacing, the rail pad stiffness and the bearing stiffness under sleepers. It is concluded that the frequency of the higher load on or under the sleeper occurred within2~3Hz and28~29Hz. Sleeper’s higher vertical vibration acceleration occurred within70~90Hz. With the improvement of train running speed, loads under the sleeper, as well as the vertical acceleration are on the rise. With the improvement of rail pad stiffness, loads under the sleeper and the sleeper vertical acceleration are on the rise. With the improvement of bearing stiffness under sleepers, loads on the sleeper and sleeper vertical acceleration are on the decline, loads under the sleeper are on the rise.Improving the concrete performance and label strength, the tensile strength of pre-stressed reinforcement, the number of pre-stressed reinforcement and optimizing pre-stressed reinforcement location can improve sleeper bearing capacity without changing the sleeper shapes and sizes. Integrated sleeper design equations and set the equivalence safety reserve between cross section under rail and in the middle as the objective function, put forward a pre-stressed reinforcement optimal location method, and put forward eight heavy haul sleeper plans. With the method, the optimal location of pre-stressed reinforcement force point from the bottom of IIIa sleeper is94.8mm. Contrast appears that increasing the number of pre-stressed reinforcement (increase the tension) is the most direct and effective method to improve the bearing capacity of sleeper with18~22%safety reserves. Other methods can have only2~5%safety reserves. |
