Maxwell Nonlinear Slider Model for Seismic Response Prediction of Semi-Active Controlled Magneto-Rheological Dampers

Abstract eng:
Magneto-rheological (MR) dampers are a promising device for seismic hazard mitigation of structural systems due to their ability to adaptively vary their damping characteristics using an appropriate control law. A majority of past research has involved small-scale MR dampers. In order to investigate the dynamic behavior of large-scale MR dampers, characterization tests have been conducted on large-scale MR dampers at the Lehigh NEES equipment site. A new MR damper model, called the Maxwell Nonlinear Slider Model (MNS), was developed using the data from these tests. The new MR damper model can independently describe the pre-yield and post-yield behavior of an MR damper, making it easier to identify the model parameters. The new damper model utilizes the Hershel-Bulkley visco-plasticity formulation to describe the post-yield behavior of the damper, and possesses the characteristics of a non-Newtonian fluid, i.e., shear thinning and thickening behavior of MR fluid. The effects of the dynamics of an MR damper associated with variable current input from a semiactive control law is integrated into the model by a nonlinear differential equation describing the eddy current effect and the magnetization behavior of damper materials. The accuracy of the new MR damper model is compared with other existing models, such as the Bouc-Wen and hyperbolic tangent models. Experimental studies are performed involving real-time hybrid simulations of complete structural systems, where MR dampers in the structure are subjected to realistic demands associated with the design basis and maximum considered earthquakes. Comparisons of the measured hysteretic response of the large-scale dampers in the tests with the predicted behavior by the MNS damper model show that the new model is able to achieve a high degree of accuracy compared to existing MR damper models under earthquake loading conditions. The MNS model enables accurate nonlinear time history analysis for the response prediction of structural systems with MR dampers to be performed.

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