Prognose der Langzeitverformungen für Gründungen von Offshore-Windenergieanlagen mit einem Akkumulationsmodell

Prediction of long-term deformations for offshore wind power plant foundations using an accumulation model.

The estimation of long-term deformations for offshore wind power plant foundations (OWPP) is still an unsolved problem. For certain foundation types (e.g. monopiles) simple models have been proposed which still have to be validated for the prototype scale - similar to the method proposed in this paper. The paper describes the estimation of long-term deformations of OWPP foundations by means of the finite-element method (FE) using an accumulation model specially developed for high-cyclic loading. The advantages, compared to the simple engineering models, are the applicability to arbitrary foundation systems and geometries (applicable to monopiles and shallow foundations) and the sound description of soil behaviour based on numerous cyclic laboratory tests. In contrast to models using decoupled springs, the interaction between adjacent soil zones and changes of the soil state parameters during cyclic loading are considered. After a simple presentation of the calculation strategy and the model equations, the calibration of the material parameters from cyclic tests is shown exemplary for an offshore-typical fine sand. The simplified estimation of the parameters based on the grain size distribution curve is also explained. Beside a discussion of the procedure for packages of cycles, exemplary FE-calculations of monopile and gravity foundations are shown.