# Evaluation of Structural Stresses of Mountain-Embedded Railway Systems
## 5 Conclusions  
In this study, a three-dimensional structural analysis model of a mountain-ERS track with a steep gradient of 180% was established. The ground coefficient was applied to simulate the ground conditions at the site where the mountain railway was constructed. By applying service loads to the factors presented in the DIN Technical Report 101 [10], the safety of mountain-ERS was evaluated, and their structural behaviors were analyzed. 1. The safety assessment revealed that the maximum principal tensile stress in the precast concrete panel, bedding layer, and subgrade layer of the mountain-ERS did not exceed the tensile strength of the concrete under the applied factored loading conditions. The stress values inside the concrete elements did not exceed their linear elastic limits. The mountain-ERS did not exhibit overall flexural deformation, and localized behavior was observed in the sections where the train load was applied to the rails. 2. With respect to the application of high-strength concrete materials for precast concrete panels, the maximum principal tensile stresses of the concrete elements increased as the elasticity modulus of the concrete increased, whereas those of the bedding and subgrade layers decreased. Applying a high-strength concrete material to the reinforcing bars inside the precast concrete panel reduced the von Mises stresses. The variations in S11 and S33 in the lower part of the concrete panel (close to the bedding layer) were attributed to the differences in the elasticity modulus. Under the load conditions considered in this structural analysis, the application of high-strength concrete material to the precast concrete panel resulted in a slight increase in the internal stresses within the concrete components, although this effect was not prominent. 3. The trends in the occurrence of S22 (vertical direction) and S11 (transverse direction) were similar when the gradient was varied. However, they induced a considerable variation in S33 (in the longitudinal direction). As the gradient of the mountain-ERS changed, the magnitude of the longitudinal component of the train load transmitted from the rail also changed considerably, indicating a difference in S33 in the uppermost part (Point A) of the precast concrete panel. The stress trends in the bedding and subgrade layers were similar. For each variable, the magnitude of the maximum principal tensile stress inside the concrete member did not exceed its tensile strength. 4. No significant differences were observed in the occurrence of S22 (in the vertical direction) when the thickness of the subgrade layer of the mountain-ERS track decreased. However, noticeable changes were observed at sites S11 and S33 in the lowest part of the subgrade layer. Even with a reduced subgrade layer thickness (compared with the initial thickness), the maximum principal tensile stresses within each concrete member did not exceed the tensile strength of the concrete material when service loads with factors were applied in the structural analysis model of this study. Based on the above results, it was concluded that the precast concrete panels of the mountain-ERS exhibited sufficient robustness against factored service loads. 5. The analysis methods applied in the structural analysis model and the results derived in this research can be utilized as basic research data for the analysis of the behavior of mountain-ERS and the optimization of sections of mountain-ERS tracks.