Centrifuge and numerical modeling of monopiles for offshore wind towers installed in clay

Offshore wind power has gained momentum as a means to diversify the world0s energy infrastructure; however, little is still known of the global stiffness behavior of the large diameter low aspect ratio monopiles which have become the foundation of choice for offshore wind towers. Traditionally, offshore foundations have been associated with gravity structures for the oil and gas industry, which in general need to resist large vertical loads with limited lateral and moment loading. However, wind towers are purposely designed to be subjected to large lateral and moment loads from the wind and waves in order to maximize power generation. Geotechnical centrifuge tests were conducted and numerical models are being developed to examine the behavior of low aspect ratio piles in clayey soils. Monopiles with aspect ratio of two are being tested in the the 150g-ton centrifuge at Rensselaer Polytechnic Institute. Initial results include momenttheta and force-displacement for various loading conditions. Numerical studies consist of finite element (FE) simulations in order to predict capacities and permanent deformations. The comparisons are to be performed in terms of the total resistance that is exerted by the soil on the caisson. FE studies allow to model capacity for different displacement fields and also to compute interactions between different loading modes. This paper outlines our progress to date including both numerical and experimental results