## 2 Numerical Analysis
### Numerical Analysis Result
The results of the deformation analysis for each material are shown in Figure 8.  
Based on our analysis of the deformation characteristics of the rubber boots, as shown in Figure 8, a strain of about \(-0.0009\) to \(0.044\) mm/mm occurred at cross-section C for the existing SBR boots. In particular, the location where the maximum strain occurred was about 30 mm from the lower surface, and the deviation of the strain was very large. On the other hand, for the EP material, a strain of about \(-0.02\) to \(0.01\) mm/mm occurred at the side cross-section C, but as shown in Figure 8, the size and deviation of the overall strain were smaller than those of the existing SBR material. In the existing SBR material, approximately 90% or more were reduced at the location where the maximum strain occurred. Figure 9 shows the relationship between displacement and strain generated by the position of the rubber boots. Figure 8: Deformation of rubber boots according to material change. Figure 9: Displacement and strain by the position of the rubber boots: (**a**) SBR displacement; (**b**) displacement; (**c**) SBR strain; (**d**) EP strain. The displacement and analysis results according to the location of each material of the rubber boot are shown in Figure 9.  
In Figure 9a,c, the SBR boots show a large deviation in displacement and strain compared with the EP rubber boots seen in Figure 9b,d. In particular, the size of the displacement and strain generated at cross sections C and D were reduced by about 83% and 90%, respectively, compared with SBR materials. Equivalent stress analysis of rubber boots according to material change  
In this study, to analyze the deformation of the rubber boots according to changes in the material and to investigate the possible extent of damage reduction, the equivalent stress of the rubber boots for each material was calculated according to the load condition, and the results are shown in Figures 10 and 11. Figure 10: Cont. Figure 11: Equivalent stress of the rubber boots made of EP: (**a**) front part A; (**b**) rear part B; (**c**) side part C; (**d**) side part D; (**e**) floor surface E.  
Figure 5:0 Equivalent stress of the rubber boots made of SBR: (**a**) front part A; (**b**) rear part B; (**c**) side part C; (**d**) side part D; (**e**) floor surface E.  
The analysis of the equivalent stress of the SBR boots, as shown in Figure 10e, revealed that the equivalent stress was concentrated at the edge of the floor boundary that was in direct contact with the concrete bed. Also, Figure 10c,d confirm that the equivalent stress is concentrated on the internal bumps of cross-sections C and D due to the behavior of the RC block in Figure 5a. For the EP rubber boot, the equivalent stress was found to be concentrated in the internal bumps on the side surfaces, as shown in Figure 11c,d. Nonetheless, as the distribution of equivalent stress, generated from the internal, was relatively evenly distributed compared with that of the existing SBR material, the phenomenon of equivalent stress concentration was eliminated in the bumps and bottom boundary, and therefore the equivalent stress was also evenly distributed in the floor boundary and surface. In Figure 11a,c, the EP boots show a small deviation in displacement and strain compared with the SBR rubber boots shown in Figure 11b,d. In particular, the size of the displacement and strain generated at cross-sections A and B were reduced by approximately 90% and 94%, respectively, compared with SBR materials. (4) Deformation Analysis of Rubber Boots According to Shape Change  
In this study, shape design and prototype formation were carried out to derive the optimal shape of the rubber boot. A total of four types of rubber boots were designed to determine the optimal shape (draft). Figure 12 shows the proposed shapes of the rubber boot. Figure 5:1 Rubber boot shape design (draft): (**a**) type 1; (**b**) type 2; (**c**) type 3; (**d**) type 4.