Smart base isolation systems for seismic response control of plan-asymmetric buildings

Base isolation is a mature technology that is widely accepted as an effective approach to earthquake hazard mitigation. Although base isolation systems are expected to generally perform well during strong earthquakes, a variety of concerns have recently been raised about such systems. One particular concern is the lateral-torsional response of plan-asymmetric base-isolated buildings with regard to near-field ground motions due to excessive bearing deformation that can occur along building corners. Conventional passive dampers have been shown to improve isolator deformations, but at the expense of increased accelerations. To improve the seismic performance of plan-asymmetric base-isolated buildings, a smart isolation system, consisting of low-damping rubber bearings, semi-active controllable fluid viscous (CFV) dampers and a supervisory fuzzy logic control (SVFLC) feedback control algorithm, is developed that can intelligently respond to disparate earthquake ground motions.; Both numerical and experimental studies are performed to validate the smart system for seismic response reduction of plan-asymmetric base-isolated structures. Numerical simulations are performed on a full-scale, eight-story, plan asymmetric (L-shaped) base-isolated building, wherein a neuro-fuzzy model of the CFV dampers is utilized to more accurately predict damper force response. Validation is culminated by an experimental study of a 1:6-scale, plan-asymmetric (L-shaped) base-isolated steel structure consisting of low-damping rubber bearings combined with two controllable fluid viscous dampers. Damper properties are independently controlled and modulated in real-time based on a SVFLC algorithm that utilizes relative displacements and velocities measured directly above the dampers. Experimental shaking table tests are used to evaluate the effectiveness of the smart isolation system in reducing the dynamic response of the isolated test structure when subjected to eight different earthquake ground motions, including both near-field and far-field earthquake records. Experimental test results demonstrate that the proposed smart isolation system shows potential for improving lateral-torsional responses as compared to passive dampers in some cases, but that realizable improvements may depend on characteristics of the ground motion.