Study On Interaction Between Water And Array Of Bodies Under Earthquake Action Or Wave Action

Most of the offshore structures in China are in strong seismic active regions,they not only bear wave loads,but also face the threat of earthquakes,and the main bearing members of many offshore structures are composed of multi-columns.To ensure the safety of the structures during construction and use,it is important to study the loading of the multi-columns under the action of earthquakes and waves and to establish an analytical method.The columns currently used in offshore structures not only use circular cross-sections,but also include non-circular cross-sections,such as elliptical,round-end,etc.Therefore,it is meaningful to establish corresponding analytical solution for multiple non-circular cross-section columns under wave action or earthquake ground motion.This thesis proposes an analytical method and the main research contents:(1)The analytical method of water-multi-columns interaction under wave and earthquake is studied,and the formulas of wave force and hydrodynamic force of the column array are established;the correctness of the proposed method is verified by comparing this method with a numerical one.The analytical method for wave force considers the scattered waves generated after the waves are incident on the column,which includes those resulting from multiple scattering problem;the analytical method for hydrodynamic force considers the radiated waves generated by the column and scattered waves generated after the radiated waves are incident on the columns.(2)The analytical method of water-multi-elliptic-bodies interaction under wave action is studied,and a wave force calculation formula is established.The method uses the Mathieu function to separate the wave pressure equation into radial and angular terms,which are substituted into the control equation and boundary conditions to obtain the undetermined coefficients.The method considers the scattered waves generated after the waves are incident on the bodies,which includes those resulting from multiple scattering problem.(3)The analytical method of interaction between water and multiple arbitrary smooth-section cylinders under wave and earthquake is studied,and the formulas of wave force and hydrodynamic force for array of arbitrary smooth-section cylinders are established.The method expands the Bessel function,Hankel function and cylinder section radius function into Fourier series and substitutes them into the wave force or hydrodynamic force function and boundary equation to determine the undetermined coefficient.The method considers multiple scattering problem as well.