Análise estática e sísmica de fundação de aerogerador em radier estaqueado

Abstract

The present dissertation proposes to evaluate the static and seismic behavior of piled rafts foundations for a wind turbine located in the city of Macau, on the northern coast of the state of Rio Grande do Norte. Static and seismic analysis were performed using the Finite Element Method, using the ABAQUS software. Initially, in the static analysis, it was observed that in a piled raft with 24 piles (originally predicted number of piles in the foundation design) the raft resisted 63% of the vertical load applied on system, which demonstrates the importance of considering the raft-soil contact in this case. It was concluded, in the static analysis, that a piled raft with 8 piles (RE8) was sufficient to fulfill the necessary safety and displacement criteria. In this case, the raft started to support 85% of the vertical load applied on foundation and the criterion that limited the reduction of more piles was the rotational stiffness, which is related to the differential settlement of the foundation. For seismic analysis, an artificial accelerogram compatible with the seismic conditions observed in Brazil was generated. It was observed that the action of the earthquake at the base of the model caused variations in the loads and vertical displacements of the foundations, as well as in their rotational and translational stiffness, throughout the duration of the event. The RE8, a proposal optimized for a situation of only static loading, experienced an increase in settlement of up to 34% during the seismic loads, as well as decreases of the same order of magnitude in its rotational and translational stiffness. This made the foundation unsuitable for the case, as it did not meet the displacement criteria imposed by the wind turbine manufacturer, as well as the possibility of structural failure due to pile traction. Finally, it was noticed that a piled raft with 20 piles (RE20) fulfilled all the design criteria during static and seismic loads and, therefore, proved to be a suitable foundation proposal for the case. It was concluded that, although the seismic loads are of low magnitude, consistent with the Brazilian territory, it is capable of causing important effects in structures sensitive to displacements and rotations, such as wind turbine foundations.