Monopiles are the most popular type of foundation for offshore wind turbines. Although capturing the effects of cyclic loading is critical to the design of monopiles, there is no recommended approach in the main design standards and no consensus in the literature as to how this can be achieved. Hence, this paper presents the step-by-step methodology and validation of a new cyclic model in sand and clay. The model consists of the degradation of monotonic soil reaction curves based on soil cyclic contour diagrams. The model is found to provide a very satisfactory match with the PISA field tests in Dunkirk dense marine sand and Cowden stiff glacial till.
