Characteristics of Track Dynamic Stiffness of Ballastless Turnout in High-Speed Railway

Based on analysis of track stiffness composition of high-speed railway ballastless turnout, a computing method is established to study the characteristics of track dynamic stiffness in switch, connecting part and frog zones. Turnout used in this study is No.18 ballastless turnout with a speed of 350km/h. Results show that when a train passes a turnout at the speed of 350km/h, all three parts mentioned above provided better vibration isolation for irregularities with wavelengths that are larger than 0.374m, 0.360m and 0.432m respectively. As for ratio of dynamic to static stiffness, nose rail has the largest; stock rail, switch rail and guide rail the second and wing rail the smallest. Each rail has only one same-phase formant when frequency is < 300Hz. Fastener stiffness and damping have great effects on the track dynamic stiffness in turnout zone, i.e. in a frequency range 0~180Hz, dynamic stiffness will increase with increases in either fastener stiffness or damping, thus it is better to set fastener damping ratio within the range 0.1~0.3. Track stiffness of a turnout area is a key parameter that influences the dynamic interaction between train and turnout. Reasonable track stiffness can decrease dynamic stress of the turnout by weakening wheel/rail interaction to improve the riding comfort of train, prolong the service life of equipment and reduce maintenance (Wu, 1999 and Lopez, 2001). Passenger dedicated railway lines (PDLs) with a total length of 18,000 km will be built in China. More than 7, 000 sets of high speed railway turnouts are needed, most of which are ballastless turnouts. Since there is little research on the characteristics of dynamic stiffness of ballastless turnout at home and abroad (Chen, 2008; Yao, 2006; Cai, 2007), it is vital to carry out such research to design reasonable track stiffness. Based on analysis of track stiffness composition of ballastless turnout, a calculation method is established to study track dynamic stiffness of switch, connecting parts and frog zones and the influence factors of track dynamic stiffness, with the goal of obtaining useful guidance and instructions for track stiffness design in turnout zones.