Suppression of wind-induced instabilities of a long span bridge by a passive deck-flaps control system: Part I: Formulation

A passive aerodynamic control method for suppression of the wind-induced instabilities of a very long-span bridge is presented. The control system consists of additional control flaps attached to the edges of the bridge deck. Rotational motion of the control flaps is governed by prestressed springs and additional cables connecting the flaps to an auxiliary transverse beam supported by the main cables of the bridge. The rotational movement of the flaps is used to modify the aerodynamic forces acting on the deck, as well as to provide aerodynamic forces on the flaps, used to stabilize the bridge. A time domain formulation of self-excited and buffeting forces is obtained through the rational function approximation of the generalized Theodorsen and Küsner functions, respectively. Performance indices assessing improvement in critical wind speed and degree of stability of the system are proposed to find the optimal configuration of the deck-flaps system. This paper lays the theoretical groundwork for the one that follows.