Geology Reference
In-Depth Information
Figure 4. Optimal points of Pareto front and design range for bilinear isolators (× Feasible range), (●
Pareto front)
from the table that bilinear base isolators provide
more reduction on building responses in com-
parison with the linear ones. In average 71.68%
reduction is obtained on building top story hori-
zontal displacement response (Pourzeynali &
Zarif, 2008).
The results obtained from linear and bilinear
modeling of the base isolators show that bilinear
model needs more stiffness for base isolators in
comparison with the linear model, while for this
case the mass of the base slab is less. The damp-
ing ratio in elastic phase of the bilinear model is
also slightly less than that of the linear one.
Table 5. Horizontal displacements (m) of the isolated building by considering non-linearity of the bear-
ings and optimized by GA
Stories of the building
Earthquakes
Base
1 st
2 nd
3 rd
4 th
5 th
6 th
7 th
8 th
9 th
10 th
Kobe
0.151
0.010
0.015
0.022
0.028
0.033
0.038
0.043
0.047
0.052
0.056
El Centro
0.289
0.025
0.040
0.054
0.061
0.064
0.067
0.070
0.071
0.073
0.074
Loma prieta
0.201
0.041
0.063
0.072
0.079
0.084
0.087
0.089
0.091
0.093
0.096
Northridge
0.271
0.024
0.038
0.051
0.058
0.062
0.065
0.067
0.068
0.068
0.068
Ensemble average
responses (m) (Optimized
by GA)
0.218
0.018
0.029
0.037
0.044
0.049
0.052
0.056
0.059
0.062
0.064
Ensemble average reduc-
tion ratios (%)
-------
34.71
49.50
56.45
66.44
63.84
67.05
68.71
70.46
69.34
71.68
 
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