Building: Any structure whose use could include shelter of
Critical Action: That component action that reaches its
elastic limit at the lowest level of lateral deflection, or
Building Performance Level: A limiting damage state,
loading, for the structure.
considering structural and nonstructural building
Damping: The exponential decay of the free vibration of
components, used in the definition of Performance
an elastic single-degree-of-freedom system due to internal
energy dissipation. Usually expressed as a percentage of
Capacity: The permissible strength or deformation for a
Component: A part or element of an architectural,
required to restrain a displaced elastic single-degree-
of-freedom system from vibration beyond the initial
electrical, mechanical, or structural system.
"at rest" position.
Component, Equipment: A mechanical or electrical
Demand: The amount of force or deformation imposed on
component or element that is part of a mechanical
an element or component.
and/or electrical system within or without a building
Design Earthquake Ground Motion: The earthquake
Component, Flexible: Component, including its
effects that buildings and structures are specifically
proportioned to resist as defined in Sec. 4.1 of NEHRP' 7.
attachments, having a fundamental period greater
than 0.06 sec.
Design Earthquake: The earthquake for use with Chapter
Component, Rigid: Component, including its
10 that is two-thirds the maximum considered earthquake.
attachments, having a fundamental period less than or
Diaphragm: A horizontal or nearly horizontal system
equal to 0.06 sec.
acting to transfer lateral forces to the vertical resisting
elements. Diaphragms are classified as either flexible or
rigid according to the requirement of Sec. 22.214.171.124 of
Plain Concrete: Concrete that is either unreinforced
or contains less reinforcement than the minimum
Diaphragm, Blocked: A diaphragm in which all
amount specified in ACI-318 for reinforced concrete.
sheathing edges not occurring on a framing member are
Reinforced Concrete: Concrete reinforced with no
supported on a fastened to blocking.
less than the minimum amount required by ACI-318,
Diaphragm Boundary: A location where shear is
prestressed or nonprestressed, and designed on the
assumption that the two materials act together in
transferred into or out of the diaphragm sheathing. Transfer
is either to a boundary element or to another force-resisting
Confined Region: That portion of a reinforced concrete
Diaphragm Chord: A diaphragm boundary element
component in which the concrete is confined by closely
spaced special transverse reinforcement restraining the
perpendicular to the applied load that is assumed to take
concrete in directions perpendicular to the applied stress.
axial stresses due to the diaphragm moment in a manner
analogous to the flanges of a beam. Also applies to shear
Construction Documents: The written, graphic,
electronic, and pictorial documents describing the design,
Diaphragm Collector: A diaphragm component provided
locations, and physical characteristics of the project.
to transfer lateral force from the diaphragm to vertical
Control Node: The node in the mathematical model of a
elements of the later-force-resisting system or to other
portions of the diaphragm.
building used to characterize mass and earthquake
Coupling Beam: A beam that is used to connect adjacent
Design Displacement: The design earthquake lateral
concrete wall piers to make them act together as a unit to
displacement, excluding additional displacement due
resist lateral loads.