to occur as a result of inelastic lateral displacements.
c.
Wall Components. Reinforced concrete and
Type 2 mechanical splices shall be permitted to be
reinforced masonry shear walls are seldom simple
used at any location.
walls. Whenever a wall has doors, windows, or other
openings, the wall must be considered as an
21.2.7 Welded splices
assemblage
of
relatively
flexible
components
(column segments and wall piers), and relatively stiff
21.2.7.1
Welded
splices
in
elements (wall segments).
reinforcement resisting earthquake-induced forces
shall conform to 12.14.3.3 and shall not be used
(1) Column segments. A column segment is a
within a distance equal to twice the member depth
vertical member whose height exceeds three times its
from the column or beam face or from sections where
thickness, and whose width is less than two and one-
yielding of the reinforcement is likely to occur as a
half times its thickness.
Its load is usually
result of inelastic lateral displacements.
predominantly axial.
Although it may contribute
little to the lateral-force resistance of the shear wall,
21.2.7.2 Welding of stirrups, ties,
its rigidity must be considered. When a column is
inserts, or other similar elements to longitudinal
built integral with a wall, the portion of the column
reinforcement required by design shall not be
that projects from the face of the wall is called a
permitted."
pilaster.
Column segments shall be designed
b.
Design Forces. Walls may be subjected to
according to ACI 318 for concrete and ACI 530 for
masonry.
both vertical (gravity) and horizontal (wind or
earthquake) forces. The horizontal forces are both in-
(2) Wall piers. A wall pier is a segment of a
plane and out-of-plane. When considered under their
wall whose horizontal length is between two and one-
in-plane loads, walls are called shear walls; when
half and six times its thickness, and whose clear
considered under their out-of-plane loads, they are
height is at least two times its horizontal length.
called normal walls.
Walls will be designed to
withstand all vertical loads and horizontal forces,
(3)
Wall segments.
Wall segments are
both parallel to and normal to the flat surface, with
components that are longer than wall piers. They are
due allowance for the effect of any eccentric loading
the primary lateral-load-resisting components in the
or overturning forces generated. Any wall, whether
shear wall.
or not intended as part of the lateral-force-resisting
system, is subjected to lateral forces unless it is
d.
In-Plane Effects. Horizontal forces at any
isolated on three sides (both ends and top), in which
floor or roof level are generally transferred to the
case it is classified as nonstructural. Any wall that is
ground (foundation) by using the strength and rigidity
not isolated will participate in shear resistance to
of shear walls (and partitions). A shear wall may be
horizontal forces parallel to the wall, since it tends to
considered analogous to a cantilever plate girder
deform under stress when the surrounding framework
standing on end in a vertical plane, where the wall
deforms.
7-8
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