Neuro-fuzzy model of hybrid semi-active base isolation system with FPS bearings and an MR damper

Full-scale experiments are carried out on a single-degree-of-freedom mass that is equipped with a hybrid base isolation system. The isolator consists of a set of four friction pendulum system (FPS) bearings and a magnetorheological (MR) damper. The 13,620 kg mass and its hybrid isolation system are subjected to various intensities of near- and far-fault earthquakes on a large shake table. The proposed fuzzy controller uses feedback from displacement or acceleration transducers attached to the structure to modulate resistance of the semi-active damper to motion. Results from several types of passive and semi-active control strategies are summarized and compared. The study shows that a combination of FPS bearings and an adjustable MR damper can provide robust control of vibration for a large full-scale structure undergoing a wide variety of seismic loads. Low power consumption, real-time feedback control, and fail-safe operation are validated in this study. A combination of the FPS bearings and the MR damper appears to offer significant possibilities for reduction of displacement and acceleration due to seismic load. A neuro-fuzzy model is used to represent behavior of the damper for various displacement, velocity, and voltage combinations that are obtained from a series of laboratory evaluation tests. Modeling of the FPS bearings is carried out with a nonlinear analytical equation and neuro-fuzzy training. Numerical simulation using neuro-fuzzy models of the MR damper and FPS bearings predict the response of the hybrid base isolation system very well. Results show that dynamic behavior of the FPS bearings and MR damper can be successfully estimated using these neuro-fuzzy models.