Dynamic response of offshore piling

Abstract

A mathematical model which describes the dynamic response of a laterally loaded offshore pile was developed in this research. Interaction effects between the pile and its water environment were considered in formulating the problem. Also considered were the nonlinear material properties of the soil and the geometrical nonlinearity of the pile. A discrete element system was utilized in idealizing the pile, soil, and water medium. Airy wave theory was used to describe the wave kinematics and Morison's equation was used to describe wave kinetics. To solve the second-order nonlinear differential equations of motion of the system, the fourth-order Runge-Kutta numerical integration method was applied. Matrix notation was used in formulating the problem and a computer program was written to provide numerical solutions. Dynamic tests were conducted on three different size model piles and the results were compared with simulated results from the mathematical model. A close comparison verified the accuracy of the model and analysis employed. Parameter studies were conducted to determine the influence of some of the significant factors on the pile's response. The effects of soil modulus of subgrade reaction, soil damping, wave-pile interaction, and axial load in the pile were investigated. A typical offshore pile was utilized in the studies.