Bridge which has been retrofitted with four PVD's to reduce vibration.
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Lead Rubber Bearing force displacement curve.
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The first building in the world to be seismically isolated with either vulcanised rubber bearings or lead-rubber bearings (1980). The William Clayton Building, Wellington, Ministry of Health Head Office, New Zealand.
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C-1 Building, Tokyo. The largest (floor area) seismically isolated building in the world.
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Ideal for seismically isolating a structure with the lead-rubber bearing carrying the weight of the structure, providing an elastic restoring force and the required damping.
Used throughout the world for seismically isolating buildings and
bridges.
Vertical load 1 to 10,000 tonne. Displacements up to 1m.
Robinson Seismic Limited's most successful product is the lead-rubber
bearing which Dr Bill Robinson invented and developed in the 1970's.
The lead-rubber bearing is world famous for being the seismic isolation
system which successfully protected the University Hospital from damage
during the 1994 Los Angeles earthquake while nearby hospitals were so
badly damaged they had to be evacuated.
The reason for the wide use of the lead-rubber bearing is illustrated by
the behaviour of the University Hospital during the January 1994 Los
Angeles earthquake. The fact is that of the ten hospitals affected by the
Los Angeles earthquake, only the hospital seismically isolated by a
lead-rubber bearing system was able to continue to operate. This
seven-storey hospital, (the University of Southern California Teaching
Hospital), underwent ground accelerations of 0.49g , while the rooftop
acceleration was only 0.21g , that is a reduction by a factor of 1.8 . The
Olive View Hospital, nearer to the epicentre of the earthquake, underwent a
top floor acceleration of 2.31g compared with its base acceleration of
0.82g , a magnification by a factor of 2.8. The Olive View Hospital,
designed to strength criteria, suffered no structural damage but had to be
closed temporarily because the high acceleration caused a water pipe to
burst on the top floor. A comparison between the hospital seismically
isolated with lead-rubber bearings , the University Teaching Hospital, and
the unisolated building, the Olive View Hospital, shows an advantage by a
factor of 1.8x2.8 ~ 5 in favour of the isolated hospital .
One kilometre closer to the epicentre than the University Teaching
Hospital, the older Los Angeles County Hospital suffered severe damage
causing the closure of a number of wings. Repair of this damage is
estimated to cost US$400 million.
Further support for the lead rubber bearing isolation system occurred in
the January 1995 Great Hanshin Earthquake where a building isolated with
the lead-rubber bearing system in the affected zone survived with no
damage or disruption to services. For this building, the Computer Centre
of the Ministry of Post and Telecommunications, preliminary results
indicate a maximum ground acceleration of 0.40g while the sixth floor
acceleration had a maximum of 0.13g , that is an attenuation by a factor
of 3.
These two examples of the behaviour of unisolated and isolated buildings
in real earthquakes, clearly illustrate the advantages of the Robinson
lead rubber bearing isolation system.
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