17 Analytical and Experimental Study of Eddy Current Damper for Vibration Suppression in a Footbridge Structure 137 (a) (b) Fig. 17.7 Finzels Reach footbridge FEM and damping force outcome. (a) Meshing of ECD. (b) ECD damping force (a) (b) Fig. 17.8 ECD of Finzels Reach footbridge magnetic flux density and current density of one copper plate demonstration. (a) Magnetic flux density. (b) Current density On the other hand, the relative magnetic flux density can be shown in Fig. 17.8a. The vector plot demonstrates the orientation of magnet flux density points in a single direction. The current density is shown in Fig. 17.8b, where it can be seen that the flowing current tends to loop in one direction. The above vector plots are selected for an instantaneous time. However, the distribution of the parameters at different time steps can change over time. This shows that the uniformity assumption might not be appropriate, but it is good enough to perform a preliminary design of the ECD. 17.5 Discussion and Conclusions This study has investigated an alternative damping source for inclusion in a TMD to mitigate vibration of a footbridge structure. Therefore, an electromagnetic damper (EMD) or Eddy current damper (ECD) has been considered for this application. Based on this idea, electromagnetic induction theory was presented, including the method of image to find out the electromagnetic damping force analytically. After the introduction of the ECD, a footbridge structure was used as a case study. The vibration serviceability assessment of the footbridge illustrated that it had a potential problem over the second and third span, and the adoption of a TMD was recommended to deal with this circumstance. An ECD was considered as the damping element of the TMD, in contrast to the use of traditional viscous damping. After the design process, a projection panel of ECD with eight single magnetic poles was presented. The FEM and analytical simulation results showed that such a damper can match the design requirement in this case. Acknowledgements The authors acknowledge the financial assistance of the UK Engineering and Physical Sciences Research Council (EPSRC) through a Leadership Fellowship Grant (Ref. EP/J004081/2) entitled “Advance Technologies for Mitigation of Human-Induced Vibration”.
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