Electrorheological-Fluid Dampers: Testing Modeling and Application in Vibration and Seismic Protection of Buildingsand Bridges

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9300827 Makris Seismic response of buildings and bridges can be substantially improved when additional dissipative units (dampers) are used. The energy dissipation ability of most dampers is based on the shearing action of some viscous or viscoelastic fluid that they contain. So far, it has been used mainly in a passive manner. Herein it is proposed to combine the concepts of passive control with the benefits of active control, to produce an optimal, yet stable and reliable damping system. This combination is feasible when the fluid within the dampers is replaced with electrorheological fluid. Electrorheological (ER) fluids can quickly undergo a drastic change in their viscosity and dynamic shear modulus when an electric field is applied. In this study it is proposed: (1) To manufacture in laboratory stable electrorheological fluids, adequate for civil engineering applications. (Several of the existing ER fluids consist of particle suspensions within a dispersant phase. After long inactive periods settling of the suspension occurs which results to loss of the fluid ER activity. (2) To develop realistic phenomenological models for the rheological behavior of the developed ER fluid, which will be experimentally calibrated. (3) To develop analytical and numerical tools to predict the damper response based on the constitutive models developed for the material behavior. These tools will lead to realistic macroscopic force displacement models for the damper unit, and possibly to the design of optimal damper geometries. (4) To extend and develop algorithms that will actively control the structural response by modifying the physical and mechanical properties of ER h) 0*0*0* fluid dampers for linear viscoelastic and nonlinear viscoplastic behavior. (5) To experimentally verify the developed models and algorithms with shake table tests on simple model structures. ***