| Summary: | The design of offshore wind turbine foundations is increasingly driven by considerations of cyclic loading. Finite element modelling of offshore wind turbine foundations subjected to cyclic loading necessitates adequate soil constitutive models. Current advanced constitutive models for sand are complex and fail to represent cyclic laboratory tests sufficiently. HySand, a new effective stress sand model for cyclic loading, has been developed within the framework of hyperplasticity. Its objective is to capture the cyclic response of sand in a simple, and sound mathematical way. HySand is a multi-surface model based on a purely frictional Matsuoka-Nakai yield surface, where plastic volumetric strain is introduced through two mechanisms: a pressure dependent contraction, and a density and anisotropy dependent dilation. HySand models sand across densities, undrained and drained behaviour, virgin loadings and pre-loaded tests, monotonic and cyclic tests. This is demonstrated through a comparison with data on Karlsruhe fine sand.
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