Identification of structure characteristics for seismic mitigation with semi-active dampers

Building structures generally contain inherently low damping capability and hence are vulnerable to seismic excitations. Control devices therefore play a useful role to provide safety to building structures subject to seismic events. In recent years semi-active dampers have gained considerable attention as a structural control device in the building construction industry. Magneto-rheological (MR) dampers, a type of semi-active damper, has proven to be more effective in seismic mitigation of building structures. The MR damper contains a controllable MR fluid whose rheological properties vary rapidly with the applied magnetic field. Although some research has been carried out on the use of MR dampers in building structures, proper design guidelines have not been established for their use by practicing engineers. This paper describes new code requirements for incorporating MR dampers in building structures in order to obtain seismic performance that will satisfy current design codes and standards. The MR damper model was developed by integrating control algorithms commonly used in MR damper modelling. Variation characteristics of the MR damper developed were computed according to a seismically excited structure as a time domain function. Building structure models, with different heights, were evaluated in real time scenarios to identify the influence of MR damper properties and their locations on seismic performance. Those parameters which contribute towards acceptable structure performance were evaluated to formulate new design rules. Finally, the performance of building structures retrofitted with MR Dampers having the desirable properties identified above, were compared with the performance of the same structures designed using current design guidance.