Boundary Elements: Diaphragm and shear wall boundary
members to which sheathing transfers forces. Boundary
members include chords and drag struts at diaphragm and
shear wall perimeters, interior openings, discontinuities,
Acceptance Criteria: Permissible values of such
and reentrant corners.
properties as drift, component strength demand, and
inelastic deformation used to determine the acceptability of
Boundary Members: Portions along wall and diaphragm
a component' projected behavior at a given Performance
edges strengthened by longitudinal and transverse
reinforcement and/or structural steel members.
Action: Sometimes called a generalized force, most
Braced Frames: An essentially vertical truss, or its
commonly a single force or moment. However, an action
equivalent, of the concentric or eccentric type that is
may also be a combination of forces and moments, a
provided in a building frame system or dual frame system
distributed loading, or any combination of forces and
to resist in-plane lateral loads.
moments. Actions always produce or cause displacements
or deformations; for example, a bending moment action
Concentrically Braced Frame (CBF): A braced
causes flexural deformation in a beam; an axial force action
frame in which the members are subjected primarily to
in a column causes axial deformation in the column; and a
torsional moment action on a building causes torsional
deformations (displacements) in the building.
Eccentrically Braced Frame (EBF): A diagonally
braced frame in which at least one end of each brace
Addition: An increase in building area, aggregate floor
frames into a beam a short distance from a beam-
area, height, or number of stories of a structure.
column joint or from another diagonal brace.
Alteration: Any construction or renovation to an existing
Ordinary Concentrically Braced Frame (OCBF): A
structure other than an addition.
steel concentrically braced frame in which members
and connections are designed in accordance with the
Appendage: An architectural component such as a
AISC Seismic Provisions.
canopy, marquee, ornamental balcony, or statuary.
Special Concentrically Braced Frame (SCBF): A
Approval: The written acceptance by the regulatory
steel or composite steel and concrete concentrically
agency of documentation that establishes the qualification
braced frame in which members and connections are
of a material, system, component, procedure, or person to
designed for ductile behavior. Special concentrically
fulfill the requirements of these provisions for the intended
braced frames shall conform to Sec. 8.2.1 or
Architectural Component Support: Those structural
V-Braced Frame: A concentric braced frame (CBF)
members or assemblies of members, including braces,
in which a pair of diagonal braces located either above
frames, struts and attachments, that transmit all loads and
or below a beam is connected to a single point within
forces between architectural systems, components, or
the clear beam span. Where the diagonal braces are
elements and the structure.
below the beam, the system also is referred to as an
"inverted V-brace frame," or "chevron bracing."
Attachments: Means by which components and their
supports are secured or connected to the seismic-force-
X-Braced Frame: A concentric braced frame (CBF)
resisting system of the structure. Such attachments include
in which a pair of diagonal braces crosses near the
anchor bolts, welded connections, and mechanical
mid-length of the braces.
Y-Braced Frame: An eccentric braced frame (EBF)
Base: The level at which the horizontal seismic ground
in which the stem of the Y is the link of the EBF
motions are considered to be imparted to the structure.
Base Shear: Total design lateral force or shear at the base.
Brittle: Systems, members, materials, and connections
that do not exhibit significant energy dissipation capacity in
Basement: A basement is any level below the first story.
the inelastic range.