Re-centering variable friction device for seismic control of structures

This paper investigates the seismic response control of a nonlinear benchmark building with a new re-centering variable friction device (RVFD). The RVFD consists of three parts: (i) a friction generation unit, (ii) a piezoelectric actuator, and (iii) shape memory alloy wires. The friction unit and piezoelectric actuator compose the first subcomponent of the hybrid device that is a variable friction damper (VFD). The clamping force of the VFD can be adjusted according to the current level of ground motion by adjusting the voltage level of piezoelectric actuators. The second subcomponent of this hybrid device consists of shape memory alloy (SMA) wires that exhibit a unique hysteretic behavior and full recovery following post-yielding deformations. In general, installed SMA devices have the ability to re-center structures upon end of the motion and VFDs can increase the energy dissipation capacity of structures. The full realization of these devices into a singular, hybrid form which complements the performance of each device is investigated. A neuro-fuzzy model is used to capture rateand temperature-dependent nonlinear behavior of the SMA components of the hybrid device. A fuzzy logic controller is developed to adjust voltage level of VFDs for favorable performance in a RVFD hybrid application. Numerical simulations of seismically excited nonlinear benchmark building are conducted to evaluate the performance of the hybrid device. Results show that the RVFD modulated with a fuzzy logic control strategy can effectively reduce interstory drifts without increasing acceleration response of the benchmark building for most cases.