A high-cycle model for sand - experimental basis, validation on model and field tests, and application to offshore wind turbine foundations
With Prof. Dr.-Ing. habil. Torsten Wichtmann, Ruhr-University Bochum
This webinar is hosted by University of Liverpool and sponsored by Optum CE.
During their lifetime offshore wind turbine (OWT) foundations are subjected to a large number of cycles caused by wind and waves. This high-cyclic loading may lead to an accumulation of deformations in the soil, resulting in a tilting of the structure, possibly endangering serviceability. The permanent deformations of the OWT foundations thus have to be accurately predicted during the design phase. Finite element calculations with a high-cycle accumulation (HCA) model may be performed for that purpose. The equations of the HCA model and the procedure applied in calculations with this model are introduced. The HCA model is based on numerous drained cyclic triaxial tests with a large number of cycles performed on sand. The most important findings of these tests regarding the influences of stress or strain amplitude, average stress, relative density, grain size distribution curve and particle shape are presented. The calibration of the HCA model based on the experimental data is shown. Deficits of the actual formulation of the HCA model related to the consideration of the cyclic preloading history are also addressed. The validation of the HCA model based on successful recalculations of element, model and field tests is demonstrated. Finally, the application of the HCA model to OWT monopile foundations is presented.