For the responses of bridge piers and pile foundations in deep water during earthquakes

hydrodynamic pressures of the waterflow acting on the structure and back action of structure deformation on waterflow belong to the classical close fluid-soild interface coupling.A 3D close waterflow-structure coupling finite element model is established

in which the Navier-Stokes equation described by arbitary Lagrange-Euler format is employed to control the waterflow movement.Dynamic responses of cylindrical structres with the top out of the water during the excitation of sine wave are investigated.The hydrodynamic pressure behaviour of the waterflow acting on the structure and dynamic effects of the waterflow are analyzed.The results indicate that the distributions of hydrodynamic pressures are dependent on the excitation frequency strongly.High frequency excitations may intensify the action of hydrodynamic pressures on the structure.The dynamic effects of waterflow may restrain the displacement and inner force responses of structures because of the viscosity and radiation daming of the waterflow.Some main factors including the structure modulus

velocity of waterflow

water height

excitation frequency and amplitude are discussed.