re-centering variable friction device for vibration control of structures subjected to near-field earthquakes

this paper proposes a re-centering variable friction device (rvfd) for control of civil structures subjected to near-field earthquakes. the proposed hybrid device has two sub-components. the first sub-component of this hybrid device consists of shape memory alloy (sma) wires that exhibit a unique hysteretic behavior and full recovery following post-transformation deformations. the second sub-component of the hybrid device consists of variable friction damper (vfd) that can be intelligently controlled for adaptive semi-active behavior via modulation of its voltage level. in general, installed sma devices have the ability to re-center structures at the 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 in this study. a neuro-fuzzy model is used to capture rate- and temperature-dependent nonlinear behavior of the sma components of the hybrid device. an optimal fuzzy logic controller (flc) is developed to modulate voltage level of vfds for favorable performance in a rvfd hybrid application. to obtain optimal controllers for concurrent mitigation of displacement and acceleration responses, tuning of governing fuzzy rules is conducted by a multi-objective heuristic optimization. then, numerical simulation of a multi-story building is conducted to evaluate the performance of the hybrid device. results show that a re-centering variable friction device modulated with a fuzzy logic control strategy can effectively reduce structural deformations without increasing acceleration response during near-field earthquakes.