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Wind and Structures
  Volume 31, Number 6, December 2020, pages 561-573
DOI: http://dx.doi.org/10.12989/was.2020.31.6.561
 


Nonparametric modeling of self-excited forces based on relations between flutter derivatives
Mitja Papinutti, Matjaž Četina, Boštjan Brank, Øyvind W. Petersen and Ole Øiseth

 
Abstract
    Unsteady self-excited forces are commonly represented by parametric models such as rational functions. However, this requires complex multiparametric nonlinear fitting, which can be a challenging task that requires know-how. This paper explores the alternative nonparametric modeling of unsteady self-excited forces based on relations between flutter derivatives. By exploiting the properties of the transfer function of linear causal systems, we show that damping and stiffness aerodynamic derivatives are related by the Hilbert transform. This property is utilized to develop exact simplified expressions, where it is only necessary to consider the frequency dependency of either the aeroelastic damping or stiffness terms but not both simultaneously. This approach is useful if the experimental data on aerodynamic derivatives that are related to the damping are deemed more accurate than the data that are related to the stiffness or vice versa. The proposed numerical models are evaluated with numerical examples and with data from wind tunnel experiments. The presented method can evaluate any continuous fitted table of interpolation functions of various types, which are independently fitted to aeroelastic damping and stiffness terms. The results demonstrate that the proposed methodology performs well. The relations between the flutter derivatives can be used to enhance the understanding of experimental modeling of aerodynamic self-excited forces for bridge decks.
 
Key Words
    aerodynamic stability/instability; bridge aerodynamics; flutter, time-domain methods; wind loads
 
Address
Mitja Papinutti:Faculty of Civil and Geodetic Engineering, University of Ljubljana, Ljubljana, Slovenia/ Department of Structural Engineering, Faculty of Engineering, Norwegian University of Science and Technology, Trondheim, Norway
Matjaž Četina, Boštjan Brank:Faculty of Civil and Geodetic Engineering, University of Ljubljana, Ljubljana, Slovenia
Øyvind W. Petersen and Ole Øiseth: Department of Structural Engineering, Faculty of Engineering, Norwegian University of Science and Technology, Trondheim, Norway
 

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