Tuned Mass Damper optimization for the mitigation of human-induced vibrations of pedestrian bridges

The design of Tuned Mass Dampers (TMD) to satisfy serviceability requirements is becoming more and more usual in the current design of footbridges. This paper analyzes the TMD design for the mitigation of pedestrian-induced vibrations with three main objectives: the introduction of a specific TMD optimization criterion for pedestrian-induced vibrations of footbridges, a critical analysis of the applicability to this specific loading scenario of classic literature optimization criteria, and a quantification of the TMD efficiency in the reduction of the footbridge acceleration. A numerical optimization criterion is proposed, based on the maximization of an efficiency factor, defined as the ratio between the uncontrolled acceleration standard deviation and the controlled one. Optimum TMD parameters are compared with classic criteria given by the literature. A possible modification of TMD parameters that permits to keep the TMD relative displacement within prescribed limits (aspect that is often a technical requirement in the TMD design) is also discussed. Monte Carlo simulations are carried out in order to confirm the validity of the standard deviation-based optimization for the reduction of the maximum dynamic response of the bridge. An application to a real footbridge is finally presented.