Active Control of the Nonlinear Vibrations in Suspension Bridges due to Wind and Vertical Moving Loads

The flexibility and low damping of the long span suspension bridges make them prone to nonlinear vibrations due to wind and moving loads. The self-excited wind forces introduce additional nonlinear excitations in addition to the geometric nonlinearity of the bridge. In order to control the nonlinear dynamic response in the suspension bridges, one has to introduce more damping forces (passive damping or active damping or both) to the bridge. In order to introduce the passive and/or active damping forces, one has to propose a control mechanism. The feasibility of using any proposed control mechanism is assessed before its approval. This paper considers the nonlinear dynamic response of a suspension bridge subjected to wind and vertical load moving with a constant speed on the bridge deck. To control the nonlinear dynamic response of the bridge, two control mechanisms are proposed. The design of the control force is made first on a linear structural model before applying it on the actual nonlinear structural model. The paper shows the controlled response of the suspension bridge using the proposed control mechanism and compare it with the uncontrolled response. The comparison will indicate the efficient control mechanism to be used for the suspension bridge. The paper concludes that, the feasibility of the proposed control mechanism depends mainly on how it creates the control forces on the bridge and it does not consume large external energy to generate the required active control force.

Keywords: Active damping; Active control; Control mechanism; Moving loads; Nonlinear vibrations; Suspension bridges; Suspended cables; Structural control; Wind loads