Geology Reference
In-Depth Information
Table 2. Stories displacements (m) in the fixed-base building (Pourzeynali & Zarif, 2008)
Stories of the building
Earthquake
1
st
2
nd
3
rd
4
th
5
th
6
th
7
th
8
th
9
th
10
th
Kobe
0.049
0.094
0.141
0.186
0.227
0.269
0.307
0.339
0.365
0.378
El Centro
0.020
0.038
0.057
0.073
0.088
0.104
0.120
0.134
0.145
0.151
Loma prieta
0.035
0.067
0.098
0.171
0.153
0.179
0.202
0.222
0.237
0.245
Northridge
0.025
0.049
0.075
0.101
0.126
0.152
0.178
0.201
0.220
0.230
Ensemble average
responses (m)
0.0302
0.0578
0.0856
0.1304
0.1340
0.1573
0.1791
0.1996
0.2004
0.2245
Table 3. Horizontal displacements (m) of the isolated building supported on elastomeric bearings with
linear behavior (Pourzeynali & Zarif, 2008)
Stories of the building
Earthquake
Base
1
st
2
nd
3
rd
4
th
5
th
6
th
7
th
8
th
9
th
10
th
Kobe
0.173
0.034
0.064
0.093
0.120
0.144
0.168
0.189
0.208
0.223
0.230
El Centro
0.094
0.018
0.033
0.048
0.060
0.072
0.084
0.094
0.103
0.111
0.114
Loma Prieta
0.139
0.026
0.049
0.071
0.090
0.108
0.126
0.141
0.154
0.165
0.170
Northridge
0.132
0.024
0.042
0.058
0.070
0.082
0.098
0.113
0.127
0.139
0.145
Ensemble average
responses (m)
0.099
0.019
0.036
0.052
0.066
0.078
0.092
0.104
0.114
0.122
0.126
Ensemble average
reduction ratios (%)
------
36.94
38.45
39.88
49.6
41.35
41.61
42.08
42.95
39.06
43.74
response. The problem associated with this type
of vibrational response protection system is that
still the base displacement in comparison with
that of the building stories is relatively high
(Pourzeynali & Zarif, 2008).
Now, using a genetic algorithm (GA) optimizer,
parameters of the isolators including their stiff-
ness, damping, and the base mass are calculated
to simultaneously minimize both the building
top story and base isolators displacements using
a multi-objective optimization procedure given
in the following section. For this purpose, the
variation domains (domain constraints) of the
design parameters are assumed as (Pourzeynali
& Zarif, 2008):
D
=
[0.10 , 1.50]
,
D
=
[0.02 , 0.30] ,
m
¾
0
b
D
=
[0.02 , 0.20]
k
0
in which
D
m0
,
D
ξb
and
D
k0
are, respectively, the
domains of mass, damping, and stiffness ratios
of the base isolators.
Multi-Objective Optimization
by Considering Linear
Behavior of the Bearings
In this section, in order to simultaneously minimize
both the building top story displacement and that
of the base isolation system, a multi-objective
GA optimizer is used. For this purpose, first us-
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