Title | Comparison of Cyclic P-Y Methods for Offshore Wind Turbine Monopiles Subjected to Extreme Storm Loading |
Publication Type | Conference Proceedings |
Year of Publication | 2015 |
Authors | Carswell W, Fontana CM, Arwade SR, Degroot DJ, Myers AT |
Conference Name | ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering |
Volume | Volume 9: Ocean Renewable Energy |
Pagination | V009T09A060, 9 pages |
Date Published | 05/2015 |
Conference Location | St. John’s, Newfoundland, Canada |
ISBN Number | 978-0-7918-5657-4 |
Other Numbers | Paper No. OMAE2015-41312 |
Keywords | Offshore Wind Turbines, Storms |
Abstract | Approximately 75% of installed offshore wind turbines (OWTs) are supported by monopiles, a foundation whose design is dominated by lateral loading. Monopiles are typically designed using the p-y method which models soil-pile resistance using decoupled, nonlinear elastic Winkler springs. Because cyclic soil behavior is difficult to predict, the cyclic p-y method accounts for cyclic soil-pile interaction using a quasistatic analysis with cyclic p-y curves representing lower-bound soil resistance. This paper compares the Matlock (1970) and Dunnavant & O’Neill (1989) p-y curve methods, and the p-y degradation models from Rajashree & Sundaravadivelu (1996) and Dunnavant & O’Neill (1989) for a 6 m diameter monopile in stiff clay subjected to storm loading. Because the Matlock (1970) cyclic p-y curves are independent of the number of load cycles, the static p-y curves were used in conjunction with the Rajashree & Sundaravadivelu (1996) p-y degradation method in order to take number of cycles into account. All of thep-y methods were developed for small diameter piles, therefore it should be noted that the extrapolation of these methods for large diameter OWT monopiles may not be physically accurate; however, the Matlock (1970) curves are still the curves predominantly recommended in OWT design guidelines. The National Renewable Energy Laboratory wind turbine analysis program FAST was used to produce mudline design loads representative of extreme storm loading. These design loads were used as the load input to cyclicp-y analysis. Deformed pile shapes as a result of the design load are compared for each of the cyclic p-ymethods as well as pile head displacement and rotation and degradation of soil-pile resistance with increasing number of cycles. |
DOI | 10.1115/OMAE2015-41312 |