Irregular Wave Effects on Dynamic Behavior of Piles

The paper presents computer-aided numerical analyses which are utilized to investigate the dynamic behavior of piles under wind-generated irregular wave loads. A pile is modeled as a single-degree-of-freedom system. The equation of motion of the system is numerically integrated using a fourth order Runge-Kutta method. The equation of motion includes shape function that is obtained approximately. It is needed to compare the solutions with another method to determine the approximation leads whether significant differences or not. For this purpose the dynamic behavior of structure is modeled by the Time History Tool of SAP 2000 and the results compared with those found by a single-degree-of-freedom system. Irregular wave is represented with equivalent regular waves with two different approaches; based on either superimposed multi-sinusoidal wave (Loading I) or significant wave (Loading II), utilizing the energy spectrum. Wave forces are obtained from Morrison Equation. The analyses account for a soil-pile interaction in a simplified way. As the lateral ground pressure changes by delving deep into the ground, soil spring stiffness also changes. Those forces are calculated separately for different depths and taken into account in both analyses. Lateral displacement of the employed pile varying with the time is obtained from analyses for Loading I and Loading II. Critical results are obtained from which loading is determined. Finally, the frequencies of the external loads and natural frequency of pile are compared to examine whether the resonance came true or not.