ANALYSIS OF THE MONOPILE FOUNDATION USING THE FINITE ELEMENT METHOD AND THE P-Y CURVES METHOD

Resumo

The Monopile type foundation has been widely used by the offshore industry as an
economically and technically optimal choice for water depths from 20 to 40m. However, with the
current trend towards the installation of wind turbines with higher capacities and deeper waters, the
need for large diameters arises, which directly affects pile-soil interaction and dynamic structure
response. Common design procedures for laterally loaded piles are based on the p-y curves method
present in the API regulation. Such procedures were developed considering small diameter piles
subjected to low loading cycles. However, recent studies have questioned the applicability of the
traditional method for the design of the most modern monopiles, which have diameters between 6 and
8m, whose behavior tends to be rigid body and not a flexible foundation, as expected when using the
curves p-y. This work aims to analyze the behavior of the foundation of a wind turbine of 5MW under
horizontal load induced by wind, waves and currents taking into account the load x displacement curve
obtained from three dimensional models in finite elements. In the construction of the models, the
elastoplastic and non-linear behavior of the soil are considered. The obtained results are later
compared with those obtained by the traditional method of the p-y curves. It is expected to show that
for the monopiles analysis of wind towers, the p-y curves can be imprecise when representing the
behavior of the soil, presenting values of displacements and rotations at the top of the monopile
significantly different from the real displacements, making necessary a method that best represents the
behavior of these structures.