Earthquake Engineering Research - HKU Libraries - The University ...

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INTRODUCTION
In recent years, the large earthquakes have frequently occurred near the urban area and brought
about enormous damage to not only building structures but also lifeline system. Especially the
damage to information equipment has great impact on city functions with the advance of
information society. Therefore it is important to take effective measures to keep the safety of
the equipment against the earthquakes.
In the previous paper *\ the excellent vibration control effect on the equipment by the device of
high-stiffness and high-damping rubber had been shown where the equipment was installed on
the upper floor of information buildings. In this study, the vibration control device of
low-stiffness and high-damping rubber has been considered through the shaking table tests
using the artificial wave made from the lower floor response of buildings against earthquakes
with seismic intensity scale MM8.
VIBRATION CONTROL DEVICE
The vibration control device is consisted of pieces of low-stiffness and high-damping laminated
rubber sized to match the equipment and is attached to the bottom of the equipment. This
rubber was designed to reduce the acceleration response at the time of an earthquake by
absorbing the vibration energy.
The characteristics of the equipment and level of the earthquake motion used in this shaking
table test are shown in Table 1. The characteristics of each low-stiffness and high-damping
rubber are shown in Table 2. Two kinds of rubber with different damping ratio were used as A
and B. Their dynamic characteristics are described in Fig. 2. The equivalent stiffness is almost
the same for type A and B. The equivalent damping factor of type A is larger than type B. The
vibration control device, the equipment system, and the raised-floor were set up on the
three-dimensional shaking table as in Fig. 1.
TABLE. 1.
CHARACTERISTICS OF THE EQUIPMENT AND TEST CASE
Test Case
Equipment size(mm)
Equipment own weight (kg)
Dummy weight (kg)
Equipment Total weight (kg)
Type of rubber
X direction
Natural Period (sec)
Y direction
Horizontal (m/sec 2 )
Earthquake motion level
Vertical (m/sec 2 )
CaseN Case A CaseB
_
0.23
0.16
700X900X2000
190.5
228.5
419.0
Type A
0,24
0.17
4-6-8
2-3-4
TypeB
0.25
0.17