## 2 Numerical Model  
### Geometry and Material Properties  
The FEM-MBS coupled model of a turnout was developed to investigate the dynamic behavior of a railway turnout subjected to dynamic impact loads. The track is modeled with FEM elements and the vehicle, and interactions between track and vehicle are defined by MBS elements. The coupling between the two models is provided by Hertzian Contact Theory. The model represents a right-hand turnout of 54E1/1:9 type consisting of an entrance, a switch, a closure panel and a crossing panel. The length is approximately 48 m. A descriptive figure of the model is illustrated in Figure 1. Two common element types, beam elements for rails and sleepers, and linear springs--viscous dampersfor substructure and rail pads--are used while modelling. The rails in the model have an equivalent rail profile compared to a standard UIC54 rail. The equivalent profile serves as an opportunity to reduce the model complexity as the stress-strain level investigation is not the main concern in the context. Furthermore, the rail surfaces are assumed to be perfectly smooth with the exception of a small irregularity representing the discontinuity found on the rail at the crossing panel in Figure 1c.  
The connectivity between rails and sleepers is enabled by rail pads. In practice, the range of stiffness values for rail pads is rather wide, between 20 and 3032 kN/mm [6; 34]. Selection of suitable rail pad is mainly based on experience and preference of the infrastructure managers. Hence, it is believed to be an effective and efficient approach to the select a rail pad stiffness regarding the similar values commonly used in the literature. In this model, a rail pad with a stiffness value of 1300 kN/mm is applied. Additionally, two stiffness values for different rail pads are collected and applied to simulate the conditions in the different reference cases [5; 10] for validation. It should be noted that the stiffness values are dynamic values obtained mostly by drop weight tests. An experimental study in [35] shows that maximum dynamic stiffness could be three times higher than static stiffness.  
The model consists of 77 sleepers and bearers including both shorter sleepers and the longer bearers. The average spacing between sleepers/bearers is 0.71 m. The sleepers/bearers have lengths varying from 2.44 to 4.7 m and supported by the ballast bed and subgrade. The ballast bed and subgrade is modeled by the use of a single-layered spring and damper couple representing the elastic foundation part of the 'beam on an elastic foundation concept' [6]. The collective stiffness and damping of this layer per normal sleeper is 45 kN/mm and 32 Ns/mm [27]. In addition, the stiffness and damping values per sleeper are adjusted along the turnout with reference to sleeper length.  
The unsprung mass seems to be the most influential variable affecting the impact forces [6; 36]. It is assumed in this study that the unsprung mass per wheel is 10 tons. The effect of the car body and inherently, the effect of consecutive bogies is neglected since they have limited effects. As a consequence, the vehicle is simplified as two rigid wheelsets and a rigid bogie. The wheelsets and the bogie are connected by linear springs and viscous dampers which represent primary suspensions. Stiffness and damping coefficients of the primary suspension are 1.15 MN/m and 2.5 kNs/m [27]. A summary of model properties could be found in Table 1.