Diffraction and Radiation Effects of the Multi-Body Pontoon System Under the Combination of Earthquakes and Waves

This study aims to elucidate the “shielding effect” of the preceding pontoon on the target pontoon in a multi-body system under multiple disasters, focusing on the influencing mechanisms of diffraction and radiation effects as well as fluid-structure interaction. A series of scaled model tests were conducted using PIV technology. The experimental results indicate that, under earthquake-wave action, the radiation load in the heave direction of the target pontoon is minimal, whereas the loads in the roll and sway directions are substantial. Both roll and sway loads exhibit sensitivity to the vibration direction and frequency of the structure, with a resonance zone for the radiation load observed. Furthermore, the vibration frequency of the structure does not significantly alter the “shielding effect” of the preceding pontoon on the radiation effect experienced by the target pontoon in the multi-body system. Due to the combined effects of multiple hazards, the stability of the flow field surrounding the target structure is closely related to its vibration direction and frequency during earthquake-wave action. The aggregation, quantity, evolution, and decay of vortices are influenced by the structural vibration behavior.