stable and predictable inelastic behavior when
built using these technologies. Buildings in many
subjected to repeated cycles of seismic loading.
countries, including Canada, Mexico, Italy, France,
Nevertheless, there is nothing inherent in these
China, England, Russia, Iran, Chile, and South
devices that guarantees better building performance.
Africa, now use these systems.
Facilities with
The addition of energy dissipation devices will only
isolation and supplemental damping systems include
improve the seismic performance of a building if the
apartment houses, nuclear power plants, government
devices have been carefully integrated into the
office buildings, highrises, commercial structures,
seismic design of the structural system, taking into
and monumental historic buildings.
consideration the dynamic characteristics of the
building, the dissipators, and the soil at the site.
(2) Applications within the U.S. In the United
States, many projects are recently completed or under
b.
Performance Objectives. Passive energy
construction. The first new base-isolated building in
systems can be used to achieve building performance
the U.S. was completed in Rancho Cucamonga,
goals ranging from a life-safety standard to a higher
California in 1985; the first seismic upgrade using
standard that would provide damage control and post-
steel yielding devices was completed in San
earthquake functionality. The life-safety standard is
Francisco, California in 1992.
The most recent
currently reflected in the minimum design lateral-
examples of seismic upgrading by base isolation
force requirements of conventional building codes.
includes
the
Oakland,
California,
City
Hall
Damage control and post-earthquake functionality
completed in 1997, and the San Francisco City Hall,
reflect higher performance goals that would provide
scheduled for completion in 1999.
A number of
additional
protection
from
structural
and
essential facilities have been built using base-
nonstructural damage and loss of function.
The
isolation systems, including the Fire Command and
discussion below compares how these various
Control Facility and the Emergency Operations
performance objectives can be met using either
Center, both in East Los Angeles, California; the
conventional design or passive control systems.
Titan Solid Rocket Motor Storage Facility at
Vandenburg Air Force Base, California; and the V.A.
(1)
Life Safety Standard.
The philosophy
Hospital in Long Beach, California.
embodied in building codes governing conventional
fixed-base construction is that structures should resist
8-2.
Design Objectives.
minor
earthquakes
without
damage;
moderate
earthquakes with nonstructural but without structural
a.
General. Passive control systems can be
damage; and major earthquakes with structural
used to achieve different design objectives or
damage but without collapse. This is often referred
performance goals ranging from a life-safety standard
to as a life-safety standard, since the objective of
to a higher standard that would provide damage
these requirements is primarily to prevent loss of life
control and post-earthquake functionality.
The
due to catastrophic failures, not to prevent costly
energy dissipation units used in passive control
damage or loss of function.
systems are generally simple devices that exhibit
8-4
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