Dynamics: Damping

Reducing floor vibration induced by walking

Fig. 17-6: Deformation of bonded layers

Fig.17-7: The test floor (Courtesy of Dr B Ellis)

Fig.17-8: Floor vibration induced by walking loads, with and without the damping layer, (Courtesy of Dr B Ellis)
Fig. 17-5: Damping devices installed on the London Millennium Footbridge

Damping can be introduced into concrete floors by sandwiching a layer of high damping material between the structural concrete floor and a protective concrete topping. This acts in a similar manner to the demonstration model described in Section 15.3.3.

During the bending of the floor induced by footfall vibrations, energy is dissipated through the shear deformation produced in the damping material by the relative deformations of the two concrete layers (Fig. 17-6). The technique was originally used to damp out vibrations of aircraft fuselage panels when the resonant frequencies of the panels were over 200 Hz.

A floor panel, 6 m by 9 m , in the steel-frame test building at the BRE Cardington Laboratory was selected for testing with and without damping layers (Fig. 17-7). A variety of comparative tests were conducted included heel-drop tests, forced vibration tests and walking tests at different paces.

Fig. 17-8 shows the comparison of acceleration-time histories induced by the same individual walking on the floor panel without and with the damping layer. The benefit of the constrained damping layer in reducing the vibration of the floor is obvious.