ANÁLISE MODAL EM AEROGERADORES OFFSHORE CONSIDERANDO A INTERAÇÃO SOLO-ESTRUTURA

Camilla Mahon Campello de Souza¹; Paulo Marcelo Vieira Ribeiro¹

¹ Universidade Federal de Pernambuco

doi:10.20906/CPS/CILAMCE2017-0805

Resumo

Offshore Wind Turbines are very sensitive structures due to their slenderness nature and because their natural frequencies are close to the excitation spectrum. Modal analysis in the project phase is important in order to minimize undesirable effects and avoid failure. With this in mind, two scenarios are proposed to describe the problem: a beam with top mass, elastic end supports, water added mass and another one, more complete, considering tower-foundation interaction. A modal analysis is performed for both cases, in which the natural frequencies are found. For the first case, an analytical solution is proposed, in which a fourth order PDE is solved considering the effects of the water, the top mass and the elastic end supports. Also, a numerical solution using a MATLAB routine, based on the Finite Element Method is suggested, and comparisons between the two methods are presented. With regard to the second approach, a numerical analysis is conducted in MATLAB, and its results are compared to the ones obtained by SAP2000. Also, is suggested a procedure that reduces the scenario with the foundation to the one with the elastic supports only, considering three types of springs: translational, rotational and cross-coupling. Comparisons between the two models are showed and important differences regarding the vibration modes of both models are discussed using data from a real Offshore Wind Turbine.

Palavras-chave: Offshore Wind Turbines; Natural Frequencies; Soil-Structure Interaction; Finite Element Method; Simplified Models; Structural Dynamics