Geology Reference
In-Depth Information
earthquake are given in Table 7 and Table 8, re-
spectively. The time history diagram of the fuzzy
tuned damping ratio of the selected optimum
STMD device is shown in Figure 17. Referring
to Table 8, it can be concluded that the results of
the STMD system are approximately 36 percent
less than those of the TMD system.
Table 9 compares the responses of the ex-
ample building equipped with STMD and TMD
control systems. It can be seen from the table that
the average values of displacement, velocity and
acceleration of the building with STMD has been
decreased approximately about 61%, 73%, and
60%, respectively. It also shows the comparison
of the performance of the TMD and STMD in
reduction of the building responses for seven
different earthquake excitations. The percentages
of reduction in Table 9 are defined as
(
and TMD control systems are studied. The isolated
building is modeled as a 2-D, planar-shear frame
having one lateral degree of freedom at each story
level; while the building equipped with STMD/
TMD is modeled as a 3-D frame having 3 degrees
of freedom, two translational and one torsional,
in each story level.
In isolated building, elastomeric bearing sup-
ports are considered as one additional degree of
freedom with three unknown parameters: base
mass, stiffness, and damping ratio. In order to
calculate the building response, the governing
equations of motion of the system are solved in
state-space. The building's top story horizontal
displacement and that of the base isolation system
are considered as the objective functions to be
simultaneously minimized. The base isolators'
mass, stiffness, and damping ratio are evaluated
using GAs which take into account the linear and
nonlinear behaviors of the isolator bearings. For
this purpose, a fast and elitist NSGA-II approach
is used to find a set of Pareto-optimal solutions.
For a numerical example, a realistic ten-story
building, located in Mashhad, Iran, was chosen and
studied under action of 18 worldwide earthquake
accelerogrames. From the results of the numerical
studies, it is found that:
1
−
x
c uc
where
x
c
is the controlled response, and
x
uc
is the
uncontrolled one.
)
CONCLUSION
In this chapter, multi-objective optimization of
the dynamic response of base-isolated building
structures, as well buildings equipped with STMD
Table 7. The optimum values of design parameters evaluated for STMD/TMD devices
max of
ξ
STMD
(
)
P
s
1
P
s
2
P
i
1
P
i
2
θ
rad
m
0
ω
d
ξ
tmd
TMD
0.009
4.12
0.12
STMD
1.82
1.79
0.59
0.82
1.52
0.009
4.01
0.33
Table 8. The values of objective functions for optimum point with lowest ||J||
2
for STMD /TMD systems
J
1
J
2
J
3
||J||
2
TMD
0.32
0.28
0.61
0.61
STMD
0.21
0.18
0.37
0.41
Search WWH ::
Custom Search