Self-Excited Aeroelastic Instability of a Bridge Deck

The self-excited loads due to the response of a suspension bridge are critical to the stability of the motion. Although buffeting loads due to the random components of the wind enter into the mean square of the response, the response is dominated by the inherent instability of the system near the critical velocity. In this study of a particular deck, experimental information in the form of quasisteady aerodynamic coefficients of an actual bridge deck is used to determine the flutter speed. This is compared to the critical speed obtained by a general unsteady aerodynamic formulation. Finally, the inability of classical airfoil theory to determine the flutter speed is demonstrated.