Ballastless - Transition Section Vertical And Dynamic Behavior Of Ballasted Track,

Ballastless-ballast track transition sections are widely existent in the linking of subgrade and bridge or subgrade and tunnel. The track transition section problem has always aroused the greatest concern with the rapid development of high-speed railway and passenger dedicated lines.Because of the mostly different configurations between ballastless track and ballast track,firstly,it would lead to the abrupt changes of the track vertical stiffness.With the changes come up to some extent,it would cause obviously different displacement when a train transit,which would change to be irregularity as the transportation increasing.The being of the irregularities would aggravate the vibration between the wheel and rail,then the problem would be more and more serious.Secondly,different subsidence would come into being at the ballastless-ballast track transition section after the track's paved in a new railway's buiding,which also lead the travelling quality to be reduced most.So,due to the ballastless-ballast track transition section problem, we should do our best to reduce the subsidence difference and set a track stiffness transition section with rational structure.The research in this thesis is about the vertical vibration characteristic of the vehicle-track at the transition section between CRTS I slab track and ballast track.Referring to the actual structure of transition section,the research is on the basis of the half-width track.On the basis of the structural characteristics of slab ballastless track,the two-layer-FEM model based on composite beam theory is established, in which the rail is simulated as a infinitely long Euler beam supported by distant springs and dampers,the slab is simulated as a short free Euler beam resting on continuous viscoelastic foundation. On the basis of the structural characteristics of ballast track, the three-layer-FEM model based on discrete viscoelastic supports theory is established, in which the effect of ballast's shearing is ignored.The vehicle is simulated as 6-freedom multi-body model,more vehicles also can be thought over.Wheel and rail are connected with the osculation theory. The equations describing the vertical vibration of the system are formulated according to the principle of total potential energy with stationary value in elastic system dynamics and the "set in right position"rule formulating matrixes and simulating program is constructed accordingly with FORTRAN. With certain sine wave periodical irregularity as vibrating resource, the vehicle-track vertical vibratory responses are analyzed,and some time-history dynamic response curves of the system are put forward,which confirm the method in this thesis is feasible and correct.On the basis of the system model,a study of parameter work is processed,which is mainly about the effects of the stiffness ration of the transition section,speed of vehicle, irregularity,direction of the travelling.By the work,the necessarity of transition section's improving is indicated and the essential reason of the existent of irregularity is opened out,the appropriate value of some main parameters are obtained at the same time.An analysis that contrasts the dynamic behavior of several kinds of stiffness setting,then the effect of improving is discussed.As a result,the impact between wheel and rail come to be a low extent. According to the value of the different subsidence at the transition section and vehicle's speed, the appropriate length of the transition section is put forward.Referring to the foregoing study and the transition section types at home and abroad ,several types of transition remedies are listed at the end of this thesis.