## 5 Conclusions  
In this study, the behaviors of turnout sleepers under dynamic loading were investigated using a three-dimensional finite element model. Additionally, the effects of variations in vehicle speed, the modulus of elasticity of sleeper materials, rail pad stiffness, and wheel load were considered. The model was verified by the results of field measurements obtained from previous studies. The results show that the sleepers under dynamic loading have a distinct behavior compared to the sleepers under static loading. Particularly, turnout bearers under the crossing nose are subjected to high asymmetrical bending moments. This dynamic effect is crucial in terms of load definitions and should be considered in design codes. Currently, there is no approved design method for railway concrete sleepers and bearers in Europe. Unlike Europe, several non-European countries use design codes for sleepers and bearers. Nevertheless, the philosophy of the design codes is based on the static loadings. Such design  
Figure 18: Bending moment distributions of specific sleepers with reference to wheel loads: (**a**) sleeper at the entrance; (**b**) sleeper under the switch blades; (**c**) sleeper at the closure panel; (**d**) sleeper under the crossing nose; (**e**) the longest sleeper; (**f**) the shortest sleeper. codes cannot address the effects of dynamic forces on the components (i.e., premature cracking of sleepers). As a consequence, this paper highlights the effects of dynamic loading on track components such as sleepers. It demonstrates that an approach, similar to that used in this paper, could be applied at the design stage to include the effects of dynamic forces. This paper also highlights different conditions affecting the responses of the sleepers under dynamic loadings. The main outcome is that the maximum positive bending moment for all cases appears to occur at the sleeper section under the rail seats at the time step when the wheel load is directly applied to the rails on that sleeper. However, the matter of the location of the maximum negative bending moment cannot be directly addressed. It could be between two loaded rails or anywhere else along the sleeper. Another finding of the study is that the magnitude of the bending moment is affected mostly by variations in vehicle speeds. The most critical part, regarding only the sleepers, shifts from the sleepers at the closure panel to the sleepers under the crossing nose with reference to vehicle speed. At lower speeds, the impact forces seem to be ineffective; therefore, the concentrated rail stiffness at the crossing nose appears to impose lower bending moments on the sleepers with a magnitude of 7 kNm, which is roughly the half of maximum bending moment of the sleepers at the closure panel. Higher speeds escalate the impact forces causing higher bending moments of the sleeper under the crossing nose. This is important, showing the effect of the dynamic loadings. It is likely that static calculations neglect this effect and will point out a single point as a critical part. Furthermore, static calculations neglect the effect of irregularities which influence magnitude of dynamic response of the sleepers significantly. Results also show that specific sleepers such as the sleepers at the closure panel and under the crossing nose have asymmetrical bending moment distributions. The magnitude of the bending moment at one loaded rail seat could be two times higher than the opposite loaded rail seat, for these sleepers. This effect could be overlooked in the static calculations which would result in under or over estimation of the forces acting on the sleepers. Parametric studies demonstrate that variations in the modulus of elasticity of the sleeper, the rail pad stiffness, and wheel load could also have a serious effect on the bending moment distributions. In general, higher values of these parameters cause higher positive and negative bending moments.