1-g Shaking Table Test Study on the Influence of Soil–Caisson Dynamic Interaction (SCDI) on the Caisson Foundation Motion

Caisson foundations are commonly used as the tower foundations in many long-span bridges. However, the seismic performance analysis of bridge structures using caisson foundations typically assumes that the tower is fixed at the base, applying the free-field ground acceleration to the base. Consequently, the impact of soil–caisson dynamic interaction (SCDI) on the caisson foundation motion is not considered. To investigate the SCDI effects on the motion of the caisson foundation, two different systems of 1 g shaking table model tests were carried out: a free-field system model test and a soil–caisson system model test. The test results show that an increase in the peak acceleration of the table input seismic wave is associated with a greater influence of SCDI on the motion of the caisson foundation. Compared with the free-field ground motion, the SCDI effects reduce the amplitude of the horizontal acceleration of the caisson foundation motion but introduce a significant rotational component. Additionally, both effects are frequency-dependent and become more significant with increasing frequency. The shaking table test study presented in this paper reveals several crucial features of SCDI that influence the motion of the caisson foundation, enhancing the comprehension of the mechanism of SCDI and providing essential data support for subsequent theoretical and numerical simulation studies.