Dynamics: Damping

Reducing footbridge vibrations induced by walking

(a)                                                                    (b)
Fig. 17-5: Damping devices installed on the London Millennium Footbridge

A total of 37 viscous dampers were installed on the London Millennium Footbridge in order to remove the lateral vibrations of the bridge which occured when people walked across the bridge. The majority of these dampers are situated beneath the bridge deck supported by transverse members (Fig. 17-5a). One end of each viscous damper is connected to the apex of a steel V brace, known as a chevron. The apex of the chevron is supported on roller bearings that provide vertical support but allow sliding in the other directions. The other ends of the chevron are fixed to the neighboring transverse members [17.5]. Viscous dampers were also installed in the planes between the cables and the deck at the piers (Figure 17-5b) to provide damping of the lateral and lateral-torsional modes of vibration.