The sensitivity of the flutter derivatives and the flutter speed to the eccentricity of the cross section

Abstract

The flutter instability analysis of a bridge deck is based on flutter derivatives determined by wind tunnel tests on a section model having two degrees of freedom, heave and pitch (hereafter referred to as the heave-pitch model). The imperfections and the eccentricity that arise during the forced sinusoidal vibration of the section yield erroneous derivatives. This paper studies the relationship between these errors and the imperfections. Rotational excitations around two eccentric axes (hereafter referred to as the pitch-pitch model) of the section model show that the determined derivatives are less error-prone to imperfections. Determining the derivatives, like angular speed flutter derivative A_2^\ast for the aeroelastic torsion moment, gives a more accurate value, so the flutter instability analysis yields a more accurate estimate of the flutter wind speed. Numerical values are presented for the case of a thin airfoil and a bluff bridge cross section.