Study On Improvement Measures Of The Beam End Deformation Allowable Value Based On Ballastless Track Static Properties

When ballastless track is laying on bridge, the deformation of beam end will cause uplift force and down force at the rail joint of the beam end nearby. The deformation of beam end also produces the rail bending stress.If the uplift force acting on the concrete slab is large, the whole concrete slab may lose stability. The problems seriously affect the safety of track structure. In this paper, some measures are researched to improve load-carrying capability of track structure. As special fasteners is set in the beam ends, the allowable values of the beam end vertical angel are studied. The main contents and contributions are as follows.1. By comparing the related high-speed railway specifications of China,Japan and Germany, the limit value of the beam end vertical angel in China specification is testified to be the strictest.. Besides, by the three vertical stiffness limit values (beam end of vertical angel, mid-span deflection, natural frequency) are compared, and the vertical angel limit value of beam end is found to play an control role.2. The finite element model for beam-track static analysis is established, and the cases with different combinations of vertical angel and vertical downward displacement in the end of beam are calculated.The results show that the combination with bearing counterclockwise rotation in one end of the beam and downward diaplacement in the other end of beam is the most unfavorable case of beam end deformation.For the most unfavorable case, controlling indexes for beam-track structure are analyzed and it can be found that the stability of bed board in beam end and uplift force of fastenersare the controlling indexes for load-carrying capability of track structure.3. The influence factors on the load-carrying capability of track structure are analyzed. The results show that overhang length of the beam end bearing and fastener joint stiffness are two major influencing factors, fastener spacing on the bridge has little effect the load-carrying capability of track structure. Addtionally, CRTS â…¡ slab track is of the best flexibility for the end of beam deformation.4. Analyzed several measures for reduced beam end track force,the result indicate that when set the joints and hinges above the upper supported structrue or introduct the transitional plate structrue between the beam end,will be on improving the track structure force play an significant effect.5. The stability of bed board in beam end and uplift force of fasteners are easy to reach their allowable value. In order to raise pullout capacity of the beam end fastener and solve the stability problem of the bed board, PBNDROL SFC fasteners with large initial deduction pressure are set near the end of the beam, and pegs are set between the bed board and beam end When these measures are adopted, the corresponding allowable values of vertical angel are obtained. The new allowable values are larger than the existing limit values in the code. Therefore, the new limit values of vertical corner of beam end can provide references for the design of vertical stiffness for high speed bridge.