In Japan, each long-rail section is generally equipped with no more than one turnout set, since no methods have yet been established to analyze the axial force of long-rails studded with two or more turnouts. To evaluate the axial force in such cases, the RTRI constituted a finite element model and proposed a method of analysis based on this. The method enables calculation of the lateral resistance required for the ballast and discussion of a method of laying long-rails studded with successive turnouts. The RTRI also performed a measurement test on a long-rail section of ballast track where two turnouts were installed without a break (Fig. 1), confirming the validity of the analysis method.
      To study the axial force characteristics of long-rails installed with a turnout on a viaduct, the RTRI then developed a program to analyze the axial force of long-rails in relation to the expansion and contraction of the viaduct beam due to temperature changes. When the turnout was laid near the beam end, the maximum rail axial force frequently exceeded the current limit value of 980kN (obtained from the longitudinal load on the long-rail in the current design standard (Fig. 2)). The relationship between the beam length, the arrangement of supports and the rail axial force was analytically clarified, making it possible to obtain the conditions for installing direct fixation turnouts in long-rail sections.

Fig. 1 A long-rail section installed with two turnouts in succession


Fig. 2 Analysis of rail axial force in a long-rail section studded with successive turnouts

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