A FE Procedure for Foundation Design of Offshore Structures – Applied to Study a Potential OWT Monopile Foundation in the Korean Western Sea

Abstract

A finite element based calculation procedure that accounts for the effect of cyclic loading of soils under undrained conditions is presented. A material model called UDCAM that uses 3D strain contour diagrams from undrained cyclic and monotonic triaxial and DSS tests is used in the procedure. The model accounts for cyclic degradation by using the cyclic strain accumulation procedure developed at NGI in the seventies. The load history is idealized by a load composition containing load parcels with constant average and cyclic loads in each parcel. The applicability of the procedure is verified by back calculating a model test of a gravity base structure (GBS) in soft clay subjected to monotonic and cyclic loading. The procedure is then used to predict the behaviour of a monopile for a potential offshore wind turbine (OWT) in the Korean Western Sea. These results are compared with results obtained with traditional beam-spring analyses.