Mitigation of Pedestrian-induced Vibrations in Suspension Footbridges via Multiple Tuned Mass Dampers

Abstract

The dynamic response of suspension footbridges to pedestrian-induced excitations and its passive mitigation, via multiple tuned mass dampers (TMDs), are investigated. First, the nonlinear equations of motion are obtained assuming finite planar motions of the suspension bridge. A suitable approximate version of the equations of motion is shown to be in agreement with existing theories and its linearization is then employed in the structural dynamics analyses. A Galerkin discretization is exploited to calculate both the free and forced dynamic response towards the design of the vibration control system. First, the leading characteristics of the bridge dynamic response are outlined. Resonant vibrations induced by the passage of pedestrians are shown to be effectively reduced using viscoelastic TMDs. As the frequencies of the lowest two modes in suspension footbridges can be very close in the proximity of the crossover phenomenon, three different design scenarios are considered: below, near and above the crossover. In particular, the influence of these scenarios on the passive control architecture is investigated.