permits large lateral deformations under seismic load.
and qualify the portion of the component, where used, as a
An isolator unit may be used either as part of or in
confined region.
addition to the weight-supporting system of the
Steel Frame Elements:
building.
Connection: A link between components or elements
Maximum Displacement: The maximum
that transmits actions from one component or element
earthquake displacement of an isolation or energy
to another component or element. Categorized by type
dissipation system, or elements thereof, excluding
of action (moment, shear, or axial), connection links
additional displacement due to actual or accidental
are frequently nonductile.
torsion.
Tie-Down System: The collection of structural
bottom of the panel zone.
connections, components, and elements that provide
Diagonal Bracing: Inclined structural members
restraint against uplift of the structure above the
isolation system.
carrying primarily axial load, employed to enable a
structural frame to act as a truss to resist lateral loads.
Total Design Displacement: The design
Dual System: A structural system included in
displacement of an isolation or energy dissipation
building with the following features:
Seismic Isolation and Energy Dissipation continued:
An essentially complete space frame provides
system, or elements thereof, including additional
support for gravity loads.
displacement due to actual and accidental torsion.
Resistance to lateral load is provided by concrete
of steel shear walls, steel eccentrically braced
Velocity-Dependent Energy Dissipation Devices:
frames (EBF), or concentrically braced frames
Devices having mechanical characteristics such that
(CBF) along with moment-resisting frames
the force in the device is dependent on the relative
(Special Moment Frames, or Ordinary Moment
velocity in the device.
Frames) that are capable of resisting at least 25%
of the lateral loads.
Wind-Restraint System: The collection of structural
elements that provides restraint of the seismic-
isolated
Joint: An area where two or more ends, surfaces, or
structure for wind loads. The wind-restraint system
edges are attached. Categorized by the type of fastener
may be either an integral part of isolator units or a
or weld used and the method of force transfer.
separate device.
Lateral Support Member: A member designed to
Seismic Response Coefficient: Coefficient Cs as
inhibit lateral buckling or lateral-torsional buckling of
determined from Sec. 5.3.2.1 of NEHRP' 7.
9
a component.
Seismic Use Group: A classification assigned to a
Link: In an EBF, the segment of a beam that extends
building based on its use as defined in Sec. 1.3 of
from column to brace, located between the end of a
NEHRP' 7.
9
diagonal brace and a column, or between the ends of
two diagonal braces of the EBF> The length of the
Shear Panel: A floor, roof, or wall component sheathed to
link is defined as the clear distance between the
act as a shear wall or diaphragm.
diagonal brace and the column face, or between the
ends of two diagonal braces.
Site Class: A classification assigned to a site based on the
types of soils present and their engineering properties as
Link Intermediate Web Stiffeners: Vertical web
defined in Sec. 4.1.2 of NEHRP' 7.
9
stiffeners placed within the link.
Site Coefficients: The values of Fa and Fv, indicated in
Link rotation angle: The angle of plastic rotation
Tables 1.4.2.3a and 1.4.2.3b, respectively.
between the link and the beam outside of the link
derived using the specified base shear, V.
Special Transverse Reinforcement: Reinforcement
composed of spirals, closed stirrups, or hoops and
supplementary cross-ties provided to restrain the concrete
C-8
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