An accurate and ready-to-use approach for the estimation of impedance functions of regular pile groups for offshore wind turbine foundations. Vertical and rocking components

The interaction factor superposition method in the determination of the vertical and rocking impedances of pile groups for jacket-supported Offshore Wind Turbines is studied. The vertical and rocking group dynamic impedances obtained by this method are compared with those computed by a previously developed continuum model. The influence of the main parameters that define the problem is also studied. In order to propose an alternative calculation solution, some expressions dependent of these parameters are fitted from an extensive selection of jacket pile group configurations. These expressions allow to estimate the vertical flexibility of the source pile and the interaction factor between a pair of piles. Subsequently, applying elastic superposition, the group impedance functions are determined. Results show that the interaction factor superposition method correctly reproduces the vertical and rocking group dynamic impedances. Therefore, for these regular pile groups with large spacing ratios, the assumption of only considering the direct interaction between pile pairs leads to accurate results. Results obtained with the proposed fitted expressions generally conduct to a good estimation, properly reproducing the variation produced by the influence of the different parameters. Thus, this superposition method and the proposed expressions can be employed to quickly and simply reproduce the vertical soil–structure interaction of this type of structures.