Experimental Evaluation of Adaptive Elastomeric Base-Isolated Structures Using Variable-Orifice Fluid Dampers

An experimental study of a base-isolated, 1:4 scale, three-story steel frame is presented. The isolation system incorporates laminated rubber (elastomeric) bearings combined with variable-orifice fluid dampers. The dynamic behavior of the variable-orifice dampers is modulated in accordance with an H∞ optimal feedback control algorithm. An experimental shaking table test program was used to evaluate the effectiveness of the variable-orifice dampers in reducing the dynamic response of the isolated test structure when subjected to both near-field and far-field earthquake records. The experimental test results demonstrate that the adaptive isolation system can significantly reduce the superstructure response compared to a conventional passive isolation system. In addition, analytical models of the isolated test structure were developed and calibrated via experimental system identification testing. Numerical simulations of the experimental tests demonstrate that the analytical models are well suited for describing the dynamic behavior of the isolated structure.