together at top and bottom, but structurally separated
from each other by vertical joints. Since all elements
(c)
Modeling parameters and numerical
in a line are tied together at the top, they must have
acceptance criteria for nonlinear procedures are
equal horizontal deflections; therefore, a horizontal
provided in Table 7-4 for members controlled by
force parallel to the line of units will be resisted by
flexure, and in Table 7-5 for members controlled by
the individual elements in proportion to relative
shear.
rigidities.
Such elements may not have equal
Expected strength, QCE, shall be
rigidities, since some may contain large openings or
(d)
determined using 1.25fy for the contribution attributed
may be of different height-width ratios.
Some
to the reinforcement in flexure and 1.0 fy in shear.
elements may deflect primarily in shear, and others
primarily in flexure.
Where significant dissimilar
deflections are found, the building elements tying the
(e)
Lower-bound strength for force-
individual units together must be analyzed to
controlled actions (e.g., length of splices, dowels, or
determine their ability to resist or accept such
embedments) shall be equal to the values provided in
deformations, including angular rotation, without
ACI 318 without a strength reduction factor, N.
losing their ability to function as ties or diaphragm
chords or footings.
Mechanical keys or sleeved
g.
Tilt-up and Other Precast Concrete Shear
dowels may be used to assist in eliminating
Walls.
differential movement of adjacent precast panels
separated by control joints where appearance and
(1) Analysis. Precast concrete shear walls
weather-tightness
are
otherwise
satisfactorily
shall be designed in accordance with Section 9.1.1.5
provided.
of FEMA 302, and shall emulate the behavior of
monolithic reinforced concrete construction. Where
(3)
Connectors for shear walls.
Past
tilt-up or precast concrete walls are used as shear
earthquakes have shown that the performance of weld
walls, the analysis is similar to that for walls of cast-
plates or other nonductile connectors has often been
in-place concrete; however, in this case, the boundary
poor, and in many cases they have resulted in
conditions become critical, and the shears between
failures. These connectors have been weak links in
precast and cast-in-place elements must be analyzed.
the shear wall connection. It is important that the
Shears between two precast elements or between a
load-bearing shear walls be more stringently or
precast element and a cast-in-place element may be
conservatively designed, since any connector failure
developed by shear keys, dowels, or welded inserts.
during an earthquake may result in progressive
The contact joint itself is a cold joint, and will be
given no shear or tension value.
(2) Joints. Precast concrete elements tend to
be structurally separate, one element from another. In
the case of precast wall construction, for instance,
these could be a series of concrete elements tied
7-25
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