STIFFNESS ASSESSMENT OF TRANSITION PIECE ON HYBRID WIND TOWER : EIGENFREQUENCY ANALYSIS OF FINITE ELEMENT MODELS

Sammanfattning: A transition piece has responsibility to transmit forces from one member to another member. But when doing it, the transition piece must be stiff enough. Studying what parameter of the transition piece is contributing to the stiffness the most, will give economic advantages. Studies on the stiffness when introducing a transition piece on a hybrid tower will be carried out with an analytical procedure through Finite element method, with the software Abaqus. A linear perturbation, with a frequency step where extraction of the eigenfrequency value will be obtained. The value will reflect the stiffness of the structure, because it has a linear relation between each other. Higher eigenfrequency means higher stiffness and vice versa. The first model (Case A) is model of a fixed tubular tower. The frequency of case A is desired because it’s stiff at the bottom. Therefore a comparison has been made when introducing the transition piece.The eigenfrequency of the tubular tower (Case A) is 0,36765 Hz. And The eigenfrequency of the structure (Case D) is 0,21964 Hz, which make a stiffness reduction of 40,3 % when introducing the transition piece. 60,6 % of the total reduction is due to the bridging ring. The most efficient change on the bridging ring that will obtain a higher stiffness on the entire structure is to increase mid-plates layers.