Special Issue; Products for Industrial Machinery - NTN

“SSB” of Sliding Aseismic Isolution Unit Multi-ply Rubber
and velocity dependency formula below based on the
data from their experiments, and these are being
considered in the structural design of seismically
isolated building structures.
Surface pressure dependency formula (for velocity
15 mm/s)
= 0.0618 -0.351
where, : surface pressure (N/mm 2 )
Velocity dependency formula (for surface pressure
15 N/mm 2 )
= 0.0173 (V/10) 0.132 where, V: velocity (mm/s)
6.2 Durability
The durability of the multi-ply rubber SSB is
indicated in Fig. 7 in terms of the trend with the friction
coefficients of the authors’ multi-ply rubber SSB. The
grouping of the friction coefficient values is fairly
stable. Therefore, a total sliding distance of 180 m for
a seismically isolating device appears to be sufficient.
8. Conclusion
The NTN R&D Center, which is shown in Photo 1,
is a typical example of a seismically isolated building
structure supported by the authors’ SSB, and Photo 2
is a view of an installed SSB. Capable of withstanding
an earthquake as severe as the Hanshin Earthquake
level, the NTN R&D Center is expected to function as
a disaster relief center for the NTN Iwata Works. NTN
remains committed to improving the reliability of our
multi-ply rubber SSBs. We have been providing our
customers with a full line of products that are capable
of withstanding conditions in a variety of seismic load
isolating applications. The NTN believes that their
products can contribute to saving human lives and
protecting property during seismic disasters.
0.15
Test
conditions
Sliding member diameter: 400 mm
Surface pressure: 15 N/mm 2
Excitation waveform: Triangular wave
Velocity: 150 mm/sec
Dynamic friction coefficient
0.12
0.09
0.06
0.03
Photo 1 Appearance of NTN R&D center
Building structure
SSB
0.00 0 30 60 90 120 150 180
Sliding distance m
Fig. 7 Durability of the friction coefficient
7. Multi-Ply Rubber SSB Variations
Each building structure needs to cope with unique
column loading considerations. Thus, NTN offers nine
standard multi-ply rubber SSB types with bearing
diameters ranging from 300 to 1300 mm.
Table 2 Specification of multi-ply rubber SSB standard series
Photos of authors
Foundation
Photo 2 Installed SSB
References
1) Multi-ply Rubber for Seismic Isolation Editorial
Committee: Handbook of Multi-ply Rubber for
Seismic Isolation, Rikoh Tosho. (In Japanese)
Bearing diameter (mm)
3001300
Long-term bearing load (kN)
1,06019,910
0.024
Friction coefficient
(15N/mm 2 standard surface pressure)
Variation in friction coefficients (%)
30
Horizontal rigidity (kN/m)
4,71222,122
Variation in horizontal rigidity (%)
20
Vertical rigidity (MN/m)
4,60730,222
Norio ITOH
Engineering Dept.
NTN Engineering Plastics Corp.
Takuya ISHII
Engineering Dept.
NTN Engineering Plastics Corp.
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