Comparison of methods for the prediction of long-time-deformations of OWEA monopile foundations in sand

In the process of renewable-energy-development the number of offshore wind parks in the North Sea and the Baltic Sea increases. The offshore wind power plants are often founded on a single large pile, a so-called monopile. The cyclic loading due to wind and waves causes an accumulation of deformation in the soil which may lead to a permanent tilting of the monopiles. Different methods have been developed for the prediction of these non-linear long-term deformations. In this study the predictions made by the various methods are compared for realistic dimensions and loadings of an offshore wind power plant as well as different densities of a non cohesive soil. The quality and the limitations of the methods were examined. The following methods were studied: the P-y-curves of the American Petroleum Institute (API) [1], a method proposed by DUHRKOP [2], the ESWM by TASAN et al. [3], the SDM by ACHMUS et al. [4] and a method which is used at the IBF (KIT), here referred to as HIA. In this article, beside the description of the different approaches, the procedure of parameter calibration will be discussed and the parameters for each method will be retrieved by laboratory tests performed on an offshore-typical fine sand. Part 2: Simulations and conclusions [5] will present and compare the deformations of the monopile foundation due to high-cyclic loading predicted by the different approaches.