## 3 Centrifuge Test Results and Discussion
Figure 12: Response of horizontal ground model corresponding to the input acceleration. (scaled to the prototype): (**a**) peak acceleration of deck plate; (**b**) horizontal residual displacement of deck plate; (**c**) maximum moment of vertical pile; and (**d**) maximum axial force of batter pile. The peak acceleration and residual displacement of the deck plate in both figures show that the response increased with the input acceleration, for both horizontal and inclined ground models. The batter piles had little effect at low input motion intensities (less than 0.1 g), although their influence increased with the input motion intensity. The batter piles decreased the residual displacement in the inclined-ground model, but more than doubled it in the horizontal-ground model. The maximum moments of the vertical piles in Figures 12 and 13 changed significantly when the batter piles were installed. Both the horizontal- and the inclined-ground models had significant axial force in the batter piles, as the vertical pile moment is reduced when a batter pile is installed because the lateral earthquake load is transmitted to the axial force. The differences in the system responses were derived to evaluate the performance of the batter piles according to the ground slope. The bar graphs in Figure 14 express the change in system response according to the installation of the batter piles. A negative value indicates that the batter piles decreased the response, while a positive value indicates an increased response. Figure 13: Response of inclined ground model corresponding to the input acceleration. (scaled to the prototype): (**a**) peak acceleration of deck plate; (**b**) horizontal residual displacement of deck plate; (**c**) maximum moment of vertical pile; and (**d**) maximum axial force of batter pile. Figure 6:0 Difference in response with and without the batter pile according to the ground slope: (**a**) peak acceleration of deck plate; (**b**) horizontal residual displacement of deck plate; and (**c**) maximum moment of vertical pile. The peak acceleration of the deck plate (Figure 14a) decreased when the batter piles were installed in all cases, except for the horizontal-ground model with 0.09 g input acceleration. The batter piles reduced the peak acceleration of the deck plate significantly as the input acceleration increased; the decrease was more significant in the inclined-ground model (up to 48%) than in the horizontal-ground model (up to 27%). The residual displacement of the deck plate (Figure 14b) increased significantly when the batter piles were installed in the horizontal-ground model but decreased in most cases for the inclined-ground model. The increase observed in the horizontal-ground model resulted from the asymmetry of the structure in the landward and seaward directions, as the batter piles were installed close to the seaward side, as shown in Figure 6:1 However, in the inclined-ground model, the residual displacement of the deck plate decreased because the batter piles constrained the structure's behavior. Figure 14c shows that the batter piles reduced the maximum moment of the vertical pile more significantly in the inclined-ground model (by up to 84%) than in the horizontal- ground model (up to 77%). A large difference was observed in the peak acceleration and residual displacement in the response based on the installation of batter piles. However, in the case of the pile's maximum moment, the difference in response to the installation of batter piles was not large. This is because the batter pile carries most of the lateral load, so the moment of the vertical piles is significantly reduced in both the horizontal and inclined ground models. Table 5 shows the system responses. For the models without batter piles, the system response was greater in the inclined-ground model (IA62) than in the horizontal-ground model (HA45). This is because an additional kinematic force may be generated in the inclined ground during an earthquake, and the system response increases significantly [18; 29].