Passive Control of Bridge Wind-Induced Instabilities by Tuned Mass Dampers and Movable Flaps

This study investigates ways to passively suppress wind-induced instabilities such as flutter and torsional divergence. The control system design study is based on a sectional flexible bridge model interacting with a constant velocity airstream. Two strategies are considered, separately and in combination. The first makes use of trailing and leading flaps adjacent to the bridge deck, the motion of which is triggered by the deck's movement through a combination of springs, dampers, and inerters at the hinged connection. Emphasis is placed on the effect of the flap hinge location and an optimization procedure is used for determining the compensator parameters that result in favorable aeroelastic properties. The second approach reexamines the efficacy and limitations of using tuned mass dampers (TMDs) placed inside the bridge deck for controlling self-excited motion. The paper then combines the two approaches and introduces a kinematic constraint between the masses of the TMD and the flaps. This combined mechanical system, the flap mass damper (FMD), combines favorable aerodynamic properties of the flaps with a driving force provided by the vibrating mass. Consequently it has the advantage of not requiring complex and often impractical linkages in order to transmit the deck motion to the flaps. Special attention is given to ensuring that the passive control system attains optimum robustness properties and maximizes tolerance to uncertainties. Uncertainties are quantified in a series of simulations showing how the alteration of the bridge's natural frequencies affect the stability of the controlled system. The Humber Bridge in the United Kingdom is chosen as an example for the numerical simulations. (C) 2017 American Society of Civil Engineers.