Response of Offshore Towers with Pile Interaction

Abstract

Interaction between piles, known as pile‐soil‐pile interaction or group effect, modifies both group stiffness and damping and, consequently, affects the dynamic properties and behavior of the offshore tower. The formulation of the pile group stiffness by means of dynamic interaction factors is outlined, frequency dependent dynamic interaction factors are presented for piles with separation (gapping), and examples of pile group stiffness and damping are given. Then, the pile group properties are included in the dynamic analysis of an offshore tower. The effects of pile‐soil‐pile interaction on tower modal properties, i.e., natural frequencies, mode shapes, and damping, as well as response to wave action, are demonstrated.