Fuzzy Friction Controllers For Semi-active Seismic Isolation Systems

Abstract

Some studies have shown that a conventional seismic isolation system may suffer from an excessive isolator displacement when subjected to a near-fault earthquake that usually has a long-period velocity pulse waveform. In order to alleviate this problem, a semi-active isolation system (SAIS) with a variable friction damper (VFD) controlled by proposed fuzzy controllers is investigated in this study. By varying the clamping force in the VFD damper, the slip force of the damper applied on the isolation system can be regulated on-line. Moreover, in order to determine the clamping force, four types of simple fuzzy controllers are developed based on the concept of antilock braking systems used in automobiles, and their isolation performances are simulated and compared. In addition, in order to assure a fair comparison, four types of earthquakes, namely far-field, weak near-fault, strong near-fault, extreme near-fault earthquakes, representing a wide variety of ground motions are considered as the ground excitations in the simulation. The numerical result shows that among the four fuzzy controllers proposed, the one that takes the ground velocity as an input variable has the best overall performance. As compared to the uncontrolled passive isolation system, the SAIS system with this controller greatly reduces the structural acceleration and base displacement responses simultaneously in a strong or extreme near-fault earthquake, whereas the controller results in a roughly equal level of acceleration response and a much less base displacement in a far-field or weak near-fault earthquake.

Experimental realisation of the real‐time controlled smart magnetorheological elastomer seismic isolation system with shake table

“…For example, a passive friction pendulum system can only cope with certain types of earthquakes because its fixed isolation period is only correlated to the radius of the concave curvature . From another perspective, the near‐fault seismic activities, which feature intense, long‐period velocity waves (usually with amplitude of 0.5 m/s and period range between 2 and 4 s), can be detrimental and induce excessive displacement response in the conventionally base‐isolated structures with a period in this range …”

“…7 From another perspective, the near-fault seismic activities, which feature intense, long-period velocity waves (usually with amplitude of 0.5 m/s and period range between 2 and 4 s), 8 can be detrimental and induce excessive displacement response in the conventionally base-isolated structures with a period in this range. 9 Recognising the aforementioned issues, researchers started seeking solutions from the perspective of "smart" base isolation system combining passive base isolation system with controllable active actuators or semiactive damping devices. 9 In the actively controlled smart base isolation system, the control action is applied via the control force generated by active actuators, [10][11][12] whereas in the isolation system with semiactive dampers, the control action is realised indirectly by altering the damping properties of the auxiliary dampers, of which the most popular semiactive damping device is magnetorheological (MR) damper.…”

“…9 Recognising the aforementioned issues, researchers started seeking solutions from the perspective of "smart" base isolation system combining passive base isolation system with controllable active actuators or semiactive damping devices. 9 In the actively controlled smart base isolation system, the control action is applied via the control force generated by active actuators, [10][11][12] whereas in the isolation system with semiactive dampers, the control action is realised indirectly by altering the damping properties of the auxiliary dampers, of which the most popular semiactive damping device is magnetorheological (MR) damper. [13][14][15][16] In the disciplines of structural control, such smart isolation system, regardless of whether augmented with an active actuator or semiactive damping devices, should be categorised as hybrid control system.…”

Development of adaptive seismic isolators for ultimate seismic protection of civil structures

“…A hybrid system [19][20][21][22][23] was proposed by combining seismic base isolator with passive damping devices, such as viscous liquid damper, friction damper and metallic yielding damper. Smart base isolation [8][9] system is also proposed by researchers through introducing active or semi-active damping device, such as piezoelectric friction damper and magnetorheological (MR) damper, into base isolation systems.…”

Development of a novel multi-layer MRE isolator for suppression of building vibrations under seismic events

“…To overcome the shortcomings of traditional passive base isolations, recent and emerging research has been exploring various options such as adding supplementary energy-dissipating members with a magnetorheological damper, or a friction or hydraulic fluid damper, to reduce the seismic response of building structures during near-field earthquakes [4][5][6][7][10][11][12]. Yoshioka et al [4] and Ramallo et al [5] proposed a combination of conventional base isolators and controllable dampers to compensate for a traditional base isolation system in extreme earthquakes.…”