Offshore wind turbines are typically supported by monopile foundations subjected to a range of loading modes, including cyclic loads from wind and wave action and rotating turbine blades. There are currently limited design methods that properly account for cyclic loading or the effects of pile loading rate within the soil-structure response. There are also limited computational approaches that integrate cyclic loading effects easily into a computational model of the turbine for assessment of long-term performance. A major research project, PICASO (PIle Cyclic AnalySis: Oxford and Ørsted), is now underway to address cyclic loading design through new theoretical models, robust calibration methods combined with validation against new field-scale pile load tests. This paper briefly outlines the design of the field testing, where identical sets of tests will be conducted on 9 by 1.22 m and 3 by 2.5 m diameter piles at two sites, with ground conditions considered analogous to offshore sites. The sites will be well characterised through a detailed site investigation including in situ testing, high quality sampling and advanced laboratory element tests. The pile tests will include monotonic loading and high-number cyclic loading, applied in a range of amplitudes, loading directions and at various rates.
Róisín M. Buckley, Byron W. Byrne, Sarah C. Martin, Ross A. McAdam, Brian B. Sheil, Amin Aghakouchak and René Lindeboom
Keywords: monopile, cyclic loading, rate effects
Publisher: DFI