The effects of earthquakes on pile-supported wharves include damage to piles by inertial forces acting on the superstructure, and damage caused by horizontal displacement of retaining walls. Piles can also be damaged through kinematic forces generated by slope failure. Such forces are significant but it is difficult to clearly explain pile damage during slope failure since the inertial force of superstructure and the kinematic force by slope failure can occur simultaneously during an earthquake. In this study, dynamic centrifuge model tests were performed to evaluate the effect of the kinematic force of the ground due to slope failure during earthquake on the behavior of a pile-supported wharf structure. Experimental results indicate that the slope failure in the inclined-ground model caused the deck plate acceleration and pile moment to be up to 24% and 31% respectively greater than those in the horizontal-ground model due to the kinematic force of the ground.

Pile-supported structures incorporating batter piles are commonly used, and can be installed both on the horizontal and inclined ground. Recent studies have considered the positive role of batter piles during earthquakes, highlighting their satisfactory contribution to structural seismic performance. However, in these structures, even though the dynamic system responses can vary greatly depending on the ground slope, few previous studies have evaluated the seismic performance of batter piles relative to the ground slope. Therefore, this study evaluates the seismic performance of pile-supported structures with batter piles, relative to the ground slope using dynamic centrifuge model tests. The acceleration, displacement, moment, and axial force of the system were experimentally derived and reviewed, and the pile moment and axial force (M–N) interaction diagrams of the pile cross-sections were analyzed. The installation of the batter piles resulted in a greater reduction in the system response in the inclined-ground model (acceleration: −48%, displacement: −50%, and moment: −84%) compared to that in the horizontal-ground model (acceleration: −27%, displacement: +650%, and moment: −77%). Overall, batter piles showed better seismic performance in the inclined-ground model than in the horizontal-ground model.

Response spectrum analysis is widely employed in the seismic design of pile-supported wharves, as it can easily determine the maximum response of a structure. The analysis typically uses virtual fixed points to model the structure, without modelling the ground, as the structure is assumed to be a frame. Virtual fixed points can adequately simulate pile responses under horizontal static loads; however, pile responses under seismic loads have not been well studied. Therefore, the dynamic centrifuge tests evaluate the applicability of response spectrum analysis, using virtual fixed points, to the seismic design of a pile-supported wharf. Comparison of results from scale models (3 × 3 groups of piles from sections of Pohang New Port, Korea) with those from the analysis showed that the response spectrum analysis using virtual fixed points does not adequately simulate the natural period or pile bending moment of a pile-supported wharf system.

Traditionally, in the codes for seismic performance evaluation of pile-supported structures (PSS), the piles are modeled using either a virtual fixed-point (VFP) method or a soil spring method, which can additionally simulate soil-pile interactions. The applicability and accuracy of the VFP method, which is originated from statically loaded piles, to evaluate piles under seismic loads has not been sufficiently explored, despite the popularity of the technique. Thus, this study evaluates the applicability of the VFP in the seismic design of PSS through pseudostatic and response spectrum analyses (RSA). Our results indicated that there was a significant difference in between the experimentally derived and VFP model-derived values for the natural period, acceleration, and moment response of the structure. This difference occurs because the soil-pile interaction is simulated through the fixed end in the VFP model.

This study fabricated friction pendulum (FP) and rolling pendulum (RP) seismic isolation systems using 3D printing to conduct 1g shaking table tests of pile-supported structure models incorporating these systems. The test results indicate that, when the FP bearing was applied to the pile heads, the acceleration response of the structure decreased once the FP bearing began to operate; as the input earthquake frequency increased (1, 3, and 10 Hz), the seismic isolation system engaged at lower input accelerations (0.16, 0.11, and 0.02 g, respectively), and the deck acceleration response decreased significantly (15, 37, and 65%, respectively) compared to that in the fixed pile head condition. Similarly, when the RP bearing was applied to the pile heads, a higher input earthquake frequency (1, 3, and 10 Hz) corresponded to a greater decrease in the deck acceleration response (82, 95, and 96%, respectively) compared to that in the fixed condition. However, a significant deck displacement was observed when using the RP bearing owing to the resonance phenomenon when the natural period of the structure was similar to the frequency of the input earthquake. Therefore, since applying RP bearing is not desirable in terms of structural displacement, it is appropriate to apply FP bearing, which can avoid resonance by changing the natural period during the operation of the seismic isolation system.