A guideline for pile driving fatigue assessment of welded joints and its application to offshore monopile installation

M. Orlando, J.M. van Wijk

IQIP, Sliedrecht, the Netherlands

Offshore wind energy has seen significant growth in recent years, driving the need for efficient and reliable foundation solutions, such as monopiles. Monopile foundations are commonly installed by means of impact pile driving. To ensure the structural integrity of the monopile foundations, which have a welded layout, correct evaluation of the cumulative fatigue damage due to the installation is essential. Currently, there is no recommended practice for modelling pile driving actions and evaluating the cumulative fatigue damage in the monopile due to impact driving. In this paper, three calculation methods with increasing complexity are presented as proposed guidelines for the engineers that will analyse this highly dynamic load case. The importance of such analysis is presented by a case study that highlights the effects of pile driving fatigue on the overall lifetime assessment of a monopile foundation. Finally, the study highlights the importance of incorporating accurate driveability predictions and realistic energy spectra for future lifetime extension calculations of a specific foundation.

Key words: Fatigue, pile driving, welded joints, stress wave analysis, monopile, finite element method