Comparison between models for the evaluation of the seismic response of offshore wind turbines on deep foundations

Abstract

In this work, a comparative study between several numerical methodologies for theseismic analysis of offshore wind turbines on deep foundations (monobuckets or monopiles)is presented. Three formulations are compared within the scope of linear elasticity. First, acoupled Boundary Element – Finite Element (BEM–FEM) model is considered for obtainingthe reference results. This methodology makes use of boundary elements to discretize the soil,while modelling the actual geometry of the hollow pile through shell finite elements. The secondmodel corresponds to a formulation based on the integral expression of the reciprocity theoremin elastodynamics and the use of specific Green’s functions for the layered half space for themodeling of soil, and the treatment of the pile as unidimensional beam elements. Finally, aBeam-on-Dynamic-Winkler-Foundation (BDWF) model is also considered as a commonly usedsimple tool for the analysis of deep foundations. The results are presented in terms of variablesof interest for the design of offshore wind turbines. From the analyses, the applicability range ofthese methodologies can be established depending on the properties of the turbine-foundation-soil system.