Analytical solution for kinematic response of offshore piles under vertically propagating S-waves

Abstract

This study develops an analytical framework to investigate the kinematic response of offshore piles under vertically propagating S-waves considering hydrodynamic pressure. The hydrodynamic pressure is calculated by using the radiation wave theory. The offshore pile and saturated soil are described by the Euler-Bernoulli beam theory and Biot's poroelastic theory, respectively. The motion of water, scattered field soil and free field soil are derived from governing equations separately. Neglecting water-soil interaction, the rigorous solution for the translational kinematic response factor and curvature ratio along the pile shaft are then obtained based on the boundary conditions of pile-soil and pile-water interaction. The rationality and accuracy of the proposed mathematical model have been verified by comparing the calculated results with the existing studies. Parametric analyses are finally conducted to investigate the influence of hydrodynamic pressure, water depth, embedment depth, slenderness ratio and soil porosity on the kinematic response of offshore piles. The results show that the frequency corresponding to the strongest kinematic response of piles will be overestimated while curvature ratio along the pile shaft will be underestimated if the hydrodynamic pressure is not taken into consideration.