Identification of flutter derivatives of bridge deck from free vibration data

This paper proposes a method of simultaneous identification of all eight flutter derivatives of bridge decks from free vibration data consisting of two modes. This method is applied to a thin box girder section and its applicability is examined. Problems involved in identifying the derivatives from free vibration are also discussed. First, the uniqueness problem in reducing the identified quantities to non-dimensionalized flutter derivatives is discussed. A method to overcome this problem is proposed and its accuracy is confirmed through numerical simulations. Second, some difficulties in identifying aerodynamic unsteady coefficients at high wind speed near the flutter onset speed are discussed. It is shown by experiments that the increase of mass and inertial moment of the sectional model leads to better accuracy in identifying the aerodynamic derivatives at higher wind speed.