While the track irregularity in turnout areas has a significant impact on wheel-rail contact, driving safety, and stability, the impact of track irregularity in front of the incoming turnout on vehicles is often overlooked. This paper fills the gaps in the study. As a result, a rigid-flexible coupled dynamic model of the vehicle and turnout is developed. The effect of various irregularities in front of the turnout on the dynamic performance of a vehicle at high speeds has been investigated based on a random sampling method. The results show that different types of track irregularities in front of the turnout have different effects on the dynamic responses of vehicles. The vehicle dynamic performance is most sensitive to short-wavelength (3 m) irregularities in front of the turnout. The alignment irregularity with long-wavelength (40 m) has a significant effect on the wheelset lateral force and lateral acceleration of the vehicle body, caused by two-point contact between the wheel and rail. The frequency range of the effect of the irregularities on the wheel-rail force, safety indicators, and accelerations of the vehicle is mainly below 200 Hz, 50 Hz, and 20 Hz. In this study, a comprehensive assessment of different irregularities is conducted, as well as a quantitative reflection on the effect of the irregularity on the dynamic indicators, providing a reference for maintenance.

The turnout is a vital railway infrastructure. Setting reasonable reduced values of the switch rail is the key to ensuring high stability and security when a vehicle passes a turnout. Poor reduced value condition leads to a car body swing or even derailment. To improve the turnout performance and reduce maintenance costs, of great importance is studying the reduced value. However, the current research did not consider wear rail profiles, and most optimizations were based on the given reduced values. Therefore, to promote dynamic performances as a vehicle passes through the turnout and to improve the traditional optimization method for the reduced value, the following investigations were carried out in this study. First, the tracking measurement of the rail profiles was conducted, and the variation law of the rail wear and the reduced value were analyzed. Further, based on the vehicle-turnout coupled model, an optimization model for the reduced value of the switch rail by the multi-island genetic algorithm was proposed. This model aims to minimize the dynamic responses. The objective functions of a vehicle passing a turnout in the main and diverging route were determined under the constraint conditions of the monotonicity of the reduced values. Finally, the optimizations were carried out in cases in which a vehicle passes on the main and diverging routes. The optimal results indicate that, after optimization, the objective function for the main and diverging routes decreased by 33.66% and 11.92%, respectively, illustrating the effectiveness of the optimization model.

A turnout is a key piece of equipment and one of the weakest links of the railway infrastructures. Continuously welded turnouts (CWTs) have been widely laid on high-speed railway bridges because of the topographic and environmental limitations, where special attention is required to ensure the safety of the high-speed railways. A real-time monitoring system will be interesting for the service status of the CWT on the bridge, which was designed and established for the first time in China. Real-time data of the service status indicators were obtained by fiber grating and video perception technologies. The data features of the monitoring results were analyzed. A regression model and backpropagation neural network model were adopted to predict the key indicators. An alarm mechanism with a static threshold and outlier diagnosis was established. The monitoring system has been in good operation state for more than 4 years, effectively ensuring railway safety and security.

The steel-spring floating slab track (SSFST) is a low-stiffness structure, sensitive to the vehicle loads. Due to the coupling effect of the superposition of adjacent bogies, it is difficult for conventional single-carriage models to meet the simulation requirements. To find a balance between computation efficiency and authenticity of analytical model results, the influence of carriage number on SSFST should be studied. Based on the finite element method and multi-body dynamics, a refined three-dimensional coupled model of multi-carriage-SSFST-tunnel was established. The difference in the dynamic response of the SSFST between single-carriage and multi-carriage models was analyzed and compared with the measured data. The field test results show that structural displacements and accelerations under the two-carriage model are much closer to the measured data. The dynamic model analysis results show that the maximum displacement of the rail and SSFST in the midspan of the slab increase by 0.48 mm and 0.34 mm under the multi-carriage model, and the vibration reduction effectiveness increases by 1.4–2.0 dB. Dynamic responses of the rail and SSFST show minor differences under the two-carriage and three-carriage models. The article is expected to provide a reference for the theoretical research, design, and layout optimization of subway SSFST.