ANÁLISE DINÂMICA DE DIFERENTES GEOMETRIAS DE FUNDAÇÕES RASAS DE AEROGERADORES

Robson Ribeiro¹; José Neres da Silva Filho¹

¹ UFRN

doi:10.20906/CPS/CILAMCE2017-0322

Resumo

The wind turbine are huge structures which are subjected to several dynamic load sources, some of those being: wind load, wave load and vibration excitation due to the rotor and rotor blades passing, for example. Those loads have a dynamic nature which is very important to the dynamic analysis of the tower-foundation system, in a way that a comparison between different types of foundation solution must contemplate this aspect. This paper aims to carry out an analysis comparing the dynamic behaviour of different wind turbine shallow foundations. To do so, several modal analyses of the tower-foundation system were made considering circular, square and octagonal footings, taking into account three different lumped models, which were: Model A, which is a cantilevered beam model, assuming that the foundation has sufficient stiffness to allow for really small base displacements; Model B, which uses global foundation stiffness derived from the elastic semi-space theory for rigid plates, and, finally, Model C, which is uses the Finite Element Method (FEM) modelling the foundation with thin-plate elements. This study was carried out to evaluate the influence of the consideration of the soil-structure interaction and the foundation stiffness in the dynamic behaviour. Additionally, for each foundation geometry, three different towers were taking in account, those being soft-soft, soft-stiff and stiff-stiff structures. This measure was taken for the sake of analysing the foundations behaviour in a wider natural vibration frequencies range. All analyses were made using the FEM software SAP 2000. The results shown that the simplified analysis considering the cantilevered beam model lead to unconservative design, once the assumption of a flexible foundation made the system way more flexible. Besides that, it was verified that the square foundation shown slightly better results when compared to the other footing geometries.

Palavras-chave: Wind turbine; Finite Element Method ; Shallow Foundations