A new design approach to isolate vibrations in monopile grippers

Abstract

Monopiles represent the most widely adopted foundation type for offshore wind turbines. The increase in turbine size, along with deployment in deeper waters and at greater distances from shore, has driven a corresponding growth in monopile dimensions. As the monopile dimensions increase, greater impact energy from the hammer is required to drive them into the seabed, generating significantly larger dynamic forces which result in a greater radial expansion of the monopile at the same axial stress. These hammer-induced forces generate shock loads that propagate through the system along various paths, inducing structural vibrations most critically through the path defined by the monopile-gripper interface, which can lead to damage of the installation equipment. To isolate these vibrations, spring elements could be introduced to decouple components from the transmitted vibrations. This, however, would affect the ability of load-baring components to support the high static loads. This research proposes a new design approach to isolate hammer-induced vibrations in the monopile gripper. The design consists of a vibration isolation system which position is proposed based on the vibration spectrum. The results demonstrate that the proposed approach can effectively attenuate vibrations in monopile grippers, thereby reducing the risk of damage to the installation equipment during impact pile driving.