ABSTRACT
Large diameter monopiles are an established foundation type for Offshore Wind Energy Converters (OWECs), although the knowledge about the behavior of these piles under cyclic loading in particular is still not comprehensive. The so-called Stiffness Degradation Method (SDM) is a numerical scheme that enables the prediction of deformation accumulation of a pile-soil system under cyclic one-way loading, using finite element simulations in connection with results of cyclic laboratory tests. Using this method, comprehensive parametric studies were carried out in order to identify the main factors affecting the cyclic pile performance. From the results, a practicable scheme could be derived that enables the estimation of the degree of cyclic increase of the pile head deformation by means of an analytical approach that captures the main influencing parameters. Herein, first a measure of pile-soil system stiffness is determined. Then, dependent on this system stiffness measure and the relative load level, cyclic accumulation parameters can be read off from diagrams. The results of field tests on steel pipe piles conducted on an intermediate scale could be regarded for an evaluation of this scheme, which shows that the proposed novel way to assess the cyclic pile deformation behavior yields plausible results.
