To improve the low-frequency vibration reduction effect of a steel spring floating slab track (FST), nonlinear quasi-zero-stiffness (QZS) vibration isolato

The purpose of this research was to investigate and improve the accuracy of the existing slab-track mat (STM) specifications in the evaluation of the vibration reduction effect. The static nonlinearity and dynamic mechanical characteristics of three types of STMs were tested, and then a modified fractional derivative Poynting–Thomson (FDPT) model was used to characterize the preload and frequency dependence. A modified vehicle–floating slab track (FST) coupled dynamic model was established to analyze the actual insertion loss. The insertion loss error evaluated by the frequency-dependent tangent stiffness increased with the increase in STM nonlinearity, and the error obtained by the third preload tangent stiffness was usually greater than that of the second preload. Compared with the secant stiffness, the second preload frequency-dependent tangent stiffness was more suitable for evaluating STMs with high-static–low-dynamics (HSLD) stiffness. In order to reflect the frequency dependence effect and facilitate engineering applications, it is recommended that second preload tangent stiffness corresponding to the natural frequency of the FST be used for evaluation. Furthermore, the insertion loss of the STMs with monotonically increased stiffness decreased as the axle load increased, and the opposite was true for the STMs with monotonically decreased stiffness. The vibration isolation efficiency of the STMs with HSLD stiffness was both stable and better than that of the STMs with monotonic stiffness.

As the requirements for reduced vibration of URT viaduct lines continue to increase, low-stiffness structures have been used extensively. When the TSI are adversely affected by low-stiffness structures, the TGI maintenance workload increases sharply. Therefore, it is necessary to predict and evaluate the TDGS of low-stiffness URT viaduct to resolve the conflict between vibration-reduction design and track maintenance. First, the train–steel spring floating slab track-U-beam viaduct model is established. Second, virtual track inspection method is used to obtain the virtual dynamic irregularities. After comparing with actual measurement results, we investigated the influence of linetype, bridge span, and static irregularities on the security indexes and the TDGS. The results showed that for curved viaduct, in addition to vertical dynamic irregularities, alignment/horizontal dynamic irregularities also have characteristic wavelengths at 1/n times bridge span. The time-domain peak values were larger than those of the straight viaduct. Moreover, as the bridge span increased, the TDGS degradation of the curve viaduct was more significant than straight viaduct. The vehicle security indexes of the low-stiffness viaduct lines have large safety margin, while TDGS indexes are close or even exceed the limit when structures are improperly designed. This could bring insurmountable difficulties to the track maintenance.