Geology Reference
In-Depth Information
Table 2. Design parameters of the fabricated MTMD
2nd-Mode
TMD
1st-Mode MTMD
Parameters
Unit 1
Unit 2
Unit 3
Unit 4
Unit 5
Designed mass, kg
µ
( )
93.2
79.9
70.0
61.0
56.0
(1.69%)
(0.31%)
Optimal frequency ratio
0.87
0.94
1.01
1.08
0.99
Designed
k
s
0
, N / m
3,361
22,746
27.8
68.2
Optimal
c
s
0
, N·s / m
ξ
( )
(2.5%)
(2.7%)
(2.9%)
(3.1%)
(3.0%)
71.0
71.0
Designed
c
s
0
, N·s / m
(
ξ
s
)
(6.5%)
(7.0%)
(7.4%)
(7.9%)
(3.1%)
Designed
α
0.1
0.0
0.36
0.60
Designed
R
j
R
v
s
( )
(0.38)
(0.40)
(0.38)
(0.34)
(0.97)
inherent damping of the first-mode MTMD was
equivalent to the case of
α
=
0.1. For the second-
mode TMD, the inherent damping ratio, 3.1%,
was very close to the optimal damping ratio, 3.0%.
Since the stiffness of the second-mode TMD was
large enough, there was no stroke problem and
stroke-reduction design was not required. Hence,
no supplementary damping was installed as well.
ing SRIM technique based on the recorded ac-
celeration measurements. With the identified
controlled and uncontrolled systems, transfer
functions of roof displacement and roof accel-
eration of the building can be obtained as shown
in Figure 6. It shows that the displacement of the
uncontrolled building is dominated by the first
mode, whereas the acceleration is dominated by
the second mode. With the MTMD installed, both
displacement and acceleration resonance peaks
of the first and second modes were significantly
reduced. Comparing with Figure 4(a), the unclear
local five peaks near the first mode of the con-
trolled system also revealed that
α
>0
for the
first-mode MTMD. On the other hand,
α
= 0
for
the second-mode TMD resulted in two clear local
peaks near the second mode.
Figure 7 presents the recorded time-history
accelerations and displacements at roof with and
without the MTMD device under the three input
excitations along with the peak values and reduc-
Building-MTMD System Tests
In this experimental study, three different ac-
celeration time histories, i.e., an artificial white
noise, the 1940 El Centro earthquake, and the
1999 Chi-Chi earthquake at NCHU, were used as
input excitations of the shaking table. The PGA
of the three inputs was scaled to 30 gal so that
the PGA effect between these input forces could
be eliminated.
After the tests, the system matrices of the
experimental building were identified by employ-
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