Geology Reference
In-Depth Information
building. From Figures 10, 11, 12, 13, 14, and 15
one can see a good correlation between the ex-
perimental and analytical responses. The floor
inter-storey response plots in Figures 10, 11, and
12 show a noisy output from the capacitance type
LVDT.
The responses of the base isolated building
with the MR damper monitored by GAFLC are
shown in Figures 16 through 23. A good agree-
ment is seen between experimental and numerical
results except in the case of isolator displacement
(Figure 16). The experimental peak displacement
in the GA-FLC case is found to be 0.0028m which
is less than simple base isolated case (without MR
damper attached). This reduction in isolator dis-
placement has resulted in the increase in the
isolator acceleration (from 6.207m/s
2
in base
isolation case to 7.95 m/s
2
in hybrid base isolation
case). But the increase is not as much as compared
to benefit obtained from reducing the base dis-
placement. Table 3 reports the comparative values
obtained in three different cases, fixed base build-
ing i.e., building without any control mechanism;
building with only base isolation and building
with hybrid isolation mechanism.
Seismic isolators reduce the super structure
drift and acceleration at the cost of increased
displacement at the base. The theory is that most
of the earthquake input energy is dissipated at the
base level with little to pass to the super structure.
But in near field seismic motions the base itself
experiences out of limit base displacement. This
on the other hand increases safety concern, as
with little moment capacity at the base, large base
deflection can topple the building or the building
may collide with nearby structures. The hybrid
Figure 10. First floor drift of simple base isolated
building without control (N. Palm Springs)
Figure 11. Second floor drift of simple base iso-
lated building without control (N. Palm Springs
Table 3. Experimental results: peak responses under N. Palm Springs earthquake
Relative Displacement (x10
-2
m)
Floor Acceleration (m/s
2
)
Test Case
Base
FF
SF
TF
Base
FF
SF
TF
Fixed Base
0.0
0.2363
0.0656
0.0259
0.00
4.1331
3.1831
4.4149
Base Isolated
16.145
0.1993
0.0520
0.0387
6.2067
3.4458
3.1298
4.0787
Hybrid
Isolation
0.2859
0.1026
0.0320
0.0235
7.9447
1.944
1.7624
2.2667
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