Electromagnetic damping for control of vibration in civil structures
Ao, Wai Kei
Thesis or dissertation
University of Exeter
Reason for embargo
Some contents of the thesis are still proceeding the journal publication
This thesis investigates an alternative solution to deal with the civil structure vibration. Non-contact electromagnetic or Eddy current damping is selected as a score of vibration suppression. Electromagnetic damping relies on the interaction between a permanent magnet and conductor. An electromagnetic damper (EMD) is applied both to a laboratory footbridge structure and 6-storey model-scale aluminium moment resisting frame (AMRF). In this first study the EMD is connected in series with an electronic shunt circuit to construct an electromagnetic shunt damper (EMSD). A robust optimisation method is applied to develop the corresponding optimal design formula of the EMSD. The principle of an EMSD is to convert mechanical energy to electrical energy. Hence, the induced electromotive force (emf) is generated by electromagnetic induction. This emf induces an amount of shunt damping, which is fedback to the structure to achieve vibration suppression. It was found that when the impedance was applied, the shunt damping feature was of a similar nature to viscous dampers. In contrast, when an RLC (resistance-inductance-capacitance) circuit is connected, the shunt damping is analogous to a tuned mass damper. A second form of EMD is Eddy current damper (ECD), which relies on a geometrical arrangement of permanent magnets and conductors to produce damping forces. The vertical and horizontal orientation of the magnet, unidirectional and alternative pole projection and moving different direction of the conductor are investigated. A theoretical study involving the infinite boundary and finite boundary (the method of images current) is carried out to obtain an analytical calculation of the damping force. On the basis of this analysis, one type of ECD prototype was physically built. A performance test was carried out to determine the damping characteristics of the ECD, which agreed with the results of the numerical analysis. In addition, the ECD was applied to control the dynamics of the 6-storey AMRF. It was found that, the ECD can effectively increase system damping and have a satisfactory control effect.
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"
Chapter 5 (Ao, W.K. and Reynolds, P. Analysis of $H_\infty$ and $H_2$ optimal design scheme for an electromagnetic damper with shunt resonant circuit. Proceedings of IMAC-XXXIII Congress, Orlando, FL, USA, 2-5 February, 2015)
Chapter 5 (Ao, W.K. and Reynolds, P. Optimal analysis, design and testing of an electromagnetic damper with resonant shunt circuit for vibration control of a civil structure. Proceeding of ICSV-23 Congress, Athens, Greece, 10-14 July, 2016)
Chapter 6 (Ao, W.K. and Reynolds, P. Analytical and experimental study of Eddy current damper for vibration suppression in a footbridge structure. Proceedings of IMAC-XXXV Congress, Hyatt Regency Orange County, Garden Grove, California, USA, 30 January-2 February, 2017
PhD in Engineering