Study On The Limit Value Of Vertical Angle Of Rotation Of Beam-end On Ballastless Bridge With Transition Track

In recent years, the high-speed railway in China has been developed rapidly. The proportion of ballastless bridge including a number of large span bridges is very high. The beam end will deform under the action of train loads, temperature load, subsidence of abutment, etc. When the additional uplift forces or down forces of fasteners caused by the deformation of beam end exceed the limit values, the fastener system will be damaged. This is an important problem for the design of ballastless bridges especially the large span ones. Aimed at improving the load-carrying capability of fastener system, load-carrying capability of fastener system with a transition track at the beam end is analyzed, and the corresponding limit values of vertical angle of rotation of beam end are studied. The main contents and contributions of the paper are as follows.(1) The load-carrying character of ballastless track structure at the beam end is analyzed and two different finite element models of ballastless bridge by using ANSYS software are established, in which one can be used for ballastless bridges without transition track, and the other can be used for the ones with transition track. It is verified that both models are feasible.(2) The load-carrying capability of ballastless track at the beam end of the two different models is compared, the results shows that the additional force of fastener system decreases remarkably by setting the transition track. The decreasing amplitude of the maximum additional down force is between22%and79%, and that of the maximum additional uplift force is between26%and78%.(3) By analyzing the factors which influence the load-carrying capability of fastener system, it can be found that the stiffness of plate and length of cantilever at the beam end have an obvious influence on the load-carrying capability of fasteners. The distance between two adjacent fasteners has a certain influence, and the height of bridge body almost has no influence on the load-carrying capability of fasteners. (4) Based on the analysis of influencing factors, the structure parameters of transition track are optimized. The result shows that the most reasonable length of transition track is5.4meters with which8pairs of fasteners can be installed. In addition the space between the gap and the support of transition track should be as large as possible.(5) The load-carrying capability of ballastless track structure located at the position of ’beam end to abutment’ and ’beam end to beam end’ is calculated, and the results are suitable for the calculation of simple support beam or large span bridge. The corresponding limit values of vertical angle of rotation of beam end are established, which are larger than the existing limit values in the code. Consequently the new limit values of vertical angle of rotation of beam end can provide references for the design of vertical stiffness for high speed bridge.