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posed to be the accelerations of the base and the top floor of the structure and the relative displacement between
the base and the first story of the structure.
The specification of the 10 degree-of -feedom structure model shown in Fig. 3 are shown in Table. 1. The no
isolation case means the case that its first damping ratio is 5%. Then the passive case 1 measns no control, and
the passive case 2 means the case where its first damping ratio is much higher than the passive 1, the passive case
3 measns on isolation with lead rubber bearing, the skyhook case means that skyhook control method is adopted
as a semi-active control The disturbance-accommodating sliding mode control (DA-SMC) case and skyhook
cace deal with the case of installing variable viscous damper between the base and the first story. The frequency
range is assumed to be less than 7 Hz.
Numerical calculation was carried out for the case that the absolute velocity is adopted as an objective
function as follows:
O lx , 1 0 0]
(16)
And in order to consider the dynamics of oil damper, Maxwell model is introduced in the numerical calculation.
Figs. 4-8 and Table.2 show the time history of the top floor acceleration and the first floor dispacement
under El Centro earthquake,and so on. From these figures the effectiveness of the DA-SMC was demonstrated.
And it was seen that the DA-SMC can reduce the maximum response of acceleraion at the top floor more than
the passive control and also reduces the residual vibration which appears in no-control.
Figure 9 shows the numerical results of the vibration transrnissibility for respective controllers. In the case of
the skyhook control the performance at the frequency range is affected, while DA-SMC is effective at the whole
frequency range.
Table, 1 Parameters of the sturucture
Fig. 3 10-DOF structure model possessing an semiactive
base isolator
Layer
1
2
3
4
5
6
1
8
9
10
Mass [t]
4981.40
3438.20
2490.60
1826.40
2033.10
2050.00
2036.90
2037.10
2066.40
2499.90
Spring constant
ft/cm]
68.20
2320.00
2820.00
2020.00
1840.00
1850.00
1600.00
1410.00
1180.00
1020.00
Coefficient of
viscous damping
[t s/cm]
0.90
12.94
1971
13.34
11.15
11.05
10.55
10.15
8.48
8.71