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Utah State Capitol
Building |
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Golden Gate Bridge,
San Francisco, California |
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Seismic
isolation is physically achieved by
placing the structure on isolators.
The isolators are laterally flexible
elements, yet they are able to carry
the vertical loads of the stucture.
Since the isolators are more flexible
than the structure, most of the lateral
movements occur in the isolators.
As a result the isolated structure
experiences less motion and reduced
forces. |
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DUE
TO THE SMALLER MOTIONS
AND LOWER FORCES IN THE
SUPERSTRUCTURE, LIVES
ARE PROTECTED, CONTENTS
ARE PRESERVED AND BUILDINGS
REMAIN OPERATIONAL. |
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The
Design Earthquake
has a 10% probability of occuring
during the lifetime of the structure.
It will measure from 6.0 to
8.0 on the Richter scale. |
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| What type of structures are isolation
candidates? |
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- Hospitals, Bridges and Emergency
Centers that require operation
during and immediately after
an earthquake.
- Structures with valuable
contents or operations such
as data centers, communmications
facilities, high-tech manufacturing
facilities and museums.
- Buildings with high occupancy
such as low to medium-rise
residences and office buildings.
- Historic structures.
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| What performance
can be expected from isolation? |
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Seismic
isolation provides superior
performance compared to a traditional
structural design. It reduces
the forces and displacements
in the structure by up to 75%.
The isolation system accomplishes
this by deforming laterally
during the earthquake. After
the earthquake this results
in a functional structure with
little or no damage. |
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| What performance
can be expected from a conventional
structure? |
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Traditional
structural design is intended
to prevent major failures and
loss of life. This design approach
does not consider immediate
occupation, the maintenance
of operation nor does it provide
for easy repair. Traditional
design relies on damage to the
structure, such as yielding
and plastic deformation to dissipate
an earthquake’s energy.
Ductile design of the yielding
members helps prevent collapse
of the structure. Inherent to
this design is the possibility
of significant damage to the
structure, contents and an inoperable
unusable structure after an
earthquake. |
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ISOLATED
STRUCTURES HAVE DEMONSTRATTED A RECORD
OF
EXCELLENT PERFORMANCE DURING EARTHQUAKES. |
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| How have
isolation systems performed
in Earthquakes? |
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The
USC Hospital
was isolated using Dynamic
Isolation Systems isolators.
The building remained
operational throughout
the 1994 Northridge Earthquake.
There was no damage to
the USC Hospital. In contrast
the Los Angeles County
Medical Center located
less than a mile away
suffered $400 million
of damage and was not
operational after the
earthquake. |
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The
Stanford Linear Accelerator
in Palo Alto California was unscathed
by the 1989 Loma Prieta earthquake.
Elsewhere on campus damage was reported
to be approximately $160 million.
The Eel
River Bridge in Humboldt
County, California, was isolated using
DIS isolators in 1988. It experienced
accelerations of 0.55g in the 1992
Petrolia Earthquake. The bridge displaced
9 inches laterally and sustained no
damage. |
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| How does isolation
provide cost savings? |
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In
bridges, the foundation design
is based on elastic forces.
Isolation reduces elastic forces
by up to 75%; this translates
into direct cost savings in
the foundation.
In
buildings, Isolation provides
cost savings over the life of
the structure. An isolated building
will be essentially undamaged
in an earthquake. By comparison
a conventional building’s
structure and contents will
be damaged. The occupants will
also experience interruption
of their businesses sometimes
for weeks or even months. |
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