A comparative study on the effectiveness of a moving versus a fixed passive damper in beam vibration mitigation

Abstract

This work compares the effect that two categories of passive dampers have on the vibratory motion of a bridge modeled as simply supported uniform beam, namely the fixed versus the moving tuned mass damper (TMD). Assuming that the suspension system of the moving vehicle performs like a TMD, its effect on the vibratory motion at points on the beam is studied by juxtaposing it with the performance of the same system placed at a specific location on the bridge span. In both cases, the vehicle suspension is modeled as a single degree-of freedom (SDOF) system with a mass, a stiffness and a damping element. Specifically, we first examine the eigenproblem of this combined structural system comprising the bridge, the moving mass and the TMD, to compute spectrograms that show the time–frequency evolution of the eigenfrequencies for both fixed and moving TMD cases. Subsequently, we examine vibrations at a point close to center span of the beam and produce energy measures to contrast fixed versus moving TMD effectiveness, which changes over time thus making it impossible to produce a concrete measure.