Techno Press
Techno Press

Wind and Structures
  Volume 27, Number 5, November 2018 , pages 293-309
DOI: https://doi.org/10.12989/was.2018.27.5.293
 

Modeling of self-excited forces during multimode flutter: an experimental study
Bartosz Siedziakoand Ole Oiseth

 
Abstract
    The prediction of multimode flutter relies, to a larger extent than bimodal flutter, on accurate modeling of the self-excited forces since it is challenging to perform experimental validation by using aeroelastic tests for a multimode case. This paper sheds some light on the accuracy of predicted self-excited forces by comparing numerical predictions of self-excited forces with measured forces from wind tunnel tests considering the flutter vibration mode. The critical velocity and the corresponding flutter vibration mode of the Hardanger Bridge are first determined using the classical multimode approach. Then, a section model of the bridge is forced to undergo a motion corresponding to the flutter vibration mode at selected points along the bridge, during which the forces that act upon it are measured. The measured self-excited forces are compared with numerical predictions to assess the uncertainty involved in the modeling. The self-excited lift and pitching moment are captured in an excellent manner by the aerodynamic derivatives. The self-excited drag force is, on the other hand, not well represented since second-order effects dominate. However, the self-excited drag force is very small for the cross-section considered, making its influence on the critical velocity marginal. The self-excited drag force can, however, be of higher importance for other cross-sections.
 
Key Words
    forced vibration test; flutter; bridge aerodynamics; section model; aerodynamic derivatives
 
Address
Bartosz Siedziakoand Ole Oiseth:Department of Structural Engineering, Norwegian University of Science and Technology, Richard Birkelands vei 1A, 7491 Trondheim, Norway

 
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