Institute for Geotechnical Engineering Research Research Projects
Accumulation of Lateral Deformation of Piles under General Cyclic Swelling and Alternating Loads (Part 1&2)

Accumulation of Lateral Deformation of Piles under General Cyclic Swelling and Alternating Loads (Part 1&2)

Led by:  Prof. Dr.-Ing. Martin Achmus
Team:  M.Sc. Dennis Frick
Year:  2020
Funding:  DFG
Duration:  01.04.2018 – 31.07.2023
Is Finished:  yes


Piles with relatively large diameters are often used to transfer horizontal or lateral loads. Such loads are usually variable and must therefore be considered as cyclical. This applies in particular to offshore piles, which are subjected to intensive cyclic loading due to wind and wave loads, i.e. with high numbers of load cycles. Cyclic horizontal loads lead to an accumulation of permanent deformations of the pile and thus to a skewed position. Although this phenomenon has been known for a long time, the exact prediction of such accumulated deformations was not the subject of practical interest until some time ago. Despite the intensive cyclic loads, this also applies to offshore practice, as piles for common offshore constructions such as drilling platforms are generally subjected to high vertical loads and the (cyclic) horizontal forces are therefore only of secondary importance.

However, this is fundamentally different for piles for the foundations of offshore wind turbines. For monopile foundations in particular, the horizontal forces from wind and waves are of the same order of magnitude as the vertical forces resulting from the tower's own weight. The horizontal forces therefore determine the pile design. In addition, relatively narrow tolerances apply to wind energy towers with regard to permanent misalignment. A reliable prediction of the permanent misalignment accumulated over the service life of the structure, taking into account the respective system and boundary conditions, is therefore crucial for the economic and safe design of such pile foundations.

The aim of the research project was to experimentally determine the relevant system properties and load parameters that significantly influence the size of the deformation accumulation of monopiles. Based on the findings from a large number of small-scale model test series and additional visualisation tests using particle image velocimetry, a new calculation approach for predicting permanent deformations of monopile foundations is to be developed.