Vibration insulation of footbridges so as to reduce human discomfort

Low frequency vibrations in footbridges is a cause of annoyance for pedestrians crossing the bridge. Bagers bro, a footbridge built in Malmö (Sweden) had several constraints in the physical design that caused the first eigenmode of the bridge to be at 1.8Hz which is a severe problem for pedestrians. Therefore the bridge was fitted with tuned mass dampers to mitigate the vibration problem. To evaluate the performance of the dampers and the accuracy in the predictions of the Finite Element (FE) Models of the bridge, an investigation trough modeling and measurements with respect to the performance of the tuned dampers fitted to the bridge has been done. The measurements were performed both with and without the mass dampers engaged. The results from the operational modal analysis of the bridge were compared with finite element simulations. The mass dampers were found to greatly improve the vibratory performance of the bridge in as much as making an otherwise almost unusable bridge acceptable.