Transient flutter analysis of bluff bodies

• Extraction of aerodynamic matrices for constant speeds and accelerations of motion.
• Extraction of aerodynamic mass.
• Nonlinear transient analysis of 3 DOF self-excited forces.
• Analytic stability curves.
• Use of the tip speed ratio for normalization.

This paper deals with the flutter theory for bridge decks and presents a new approach for the determination of 27 time domain dynamic force coefficients using forced motion of the deck section at either constant absolute speed (triangular wave form) or constant absolute acceleration (parabolic wave form). These coefficients are then introduced in a transient nonlinear flutter analysis where the wind speed is varied in order to predict the stability curve of a 3 degrees of freedom deck sections. This allows for considering the nonlinear nature of the flutter phenomenon, i.e. its variation according to multiple quantities (wind speed, frequency of motion, amplitude of motion, angle of attack, etc.), when predicting flutter amplitude at any wind speed. Results show good agreement with predictions from complex eigenvalue analysis and the stabilization of flutter was observed at different levels of vibration according to the wind speed. The effect of the aerodynamic mass is also studied and its non-inclusion is shown to lead to possible non-conservative results.