Cyclic loading response of monopile foundations in cohesionless soils

Abstract

Most offshore wind farms around Europe are being constructed with monopile foundations. Whilst there is some knowledge transfer from oil and gas design there are also a number of key differences, which means new design guidelines are needed. This paper outlines some of the key issues confronting the offshore wind turbine foundation designer and concentrates on the effect of cyclic loading. It presents experimental results from a series of 1 g model tests, following on from the work of Leblanc et al. (2010a). The tests aim at further exploring a framework for calculating the long term accumulated rotation. The results confirm the phenomenological laws proposed by Leblanc et al. (2010a) for the accumulated rotation and the cyclic secant stiffness. The results also highlight that in addition to the relative density and load characteristics, the accumulated rotation and the secant stiffness appear to be dependent on the sand properties.