During the past decade a number of researchers have investigated the behavior of magneto-rheological (MR) dampers and semi-active control laws associated with using these devices for earthquake hazard mitigation of civil engineering structural systems. A majority of this research has involved reduced-scale MR dampers. A new MR damper model is developed based on full-scale damper characterization tests. The new MR damper model can independently describe the pre-yield and post-yield behavior of an MR damper, simplifying the process to identify the parameters for the model. The model utilizes the Hershel-Bulkley visco-plasticity to describe the post-yield behavior with shear thinning and thickening of the MR fluid. A nonlinear differential equation is proposed to describe the dynamics of an MR damper associated with variable current input. The accuracy of the new MR damper model is compared with existing MR damper models and experimental tests results. The comparisons show that the new model can achieve better accuracy in predicting damper behavior.
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