Geology Reference
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Figure 28. Base isolator and third-floor displacement and acceleration responses under Big Bear earth-
quake for clipped optimal based MR damper monitoring
celeration responses are shown together for better
comparison. The peak displacement response of
the isolator in simple isolation condition has been
found to be 0.1229m, which is reduced to 0.0070m
by the DI monitored MR damper. The third floor
time histories also show a decrease displacement
response from 0.0020m in uncontrolled condition
to 0.0011m in MR damper controlled case.
The acceleration response at the isolator level
is increased whereas at the superstructure it is
reduced due to the implementation of MR damp-
er. Since the MR damper decreases the isolator
displacement, the isolator acceleration increases.
The base acceleration of 2.3214m/s
2
in uncon-
trolled case is increased to 6.5054m/s
2
in the MR
controlled case. This rise is due to some sudden
peaks in the acceleration response. Figure 30
reveals that this is not always the case all along
the time history of the input excitation. For the
third floor the acceleration is reduced from 2.3631
m/s
2
to 1.6068m/s
2
.
Figure 31 shows the input voltage to the MR
damper and the corresponding control force at
the damper location. It is to be noted that the
maximum allowed input voltage is not supplied
for all the time, which is observed in the clipped
optimal case.
Base isolated structures behave as a rigid mass
over the base under seismic ground motion (Cho-
Figure 29. Voltage input and control force under
Big Bear earthquake for clipped optimal based
MR damper monitoring
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