Figure : Friction controllable bearing tested by Feng
[28].
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HYBRID PROTECTION SYSTEM
In case of near-field earthquakes, such as Northridge, Kobe and Chi-Chi
earthquakes, the high peak acceleration and high velocity pulse with
long period, passive base isolation systems are not sufficient enough,
although for moderate to low magnitude earthquakes it is sufficient.
Hybrid systems are developed to improve the performance of structures in
high magnitude near field earthquakes. A hybrid system is a combined
application of passive, active and semi-active systems. Research in the
area of hybrid control systems has focused primarily on two
classifications of systems: (1) hybrid mass damper systems; and (2)
hybrid base isolation. Most of the work on hybrid controls in the United
States has been focused on combining base isolation with some form of
active control to limit excessive displacements [14].
The common usage of the term ”hybrid control” implies the combined use
of active and passive control systems. For example, a structure equipped
with distributed viscoelastic damping supplemented with an active mass
damper on or near the top of the structure, or a base isolated structure
with actuators actively controlled to enhance performance.