(3) Boundary zone requirements for special
Section 9.1.1.13 in FEMA 302 modifies the boundary
reinforced concrete shear walls.
zone provisions in Section 21.6.6 of ACI 318 with
more explicit statements regarding when boundary
(a) Boundary zones are required for special
zones are required; the design of boundary zones; and
reinforced concrete shear walls, except where the
when the boundary zone is no longer required.
following conditions exist.
(c) Wall boundary elements may also occur
in the building frame system and the dual system
'
1. Pu < 0.10 Ag f c for geometrically
where the usual configuration is to place the shear
'
symmetrical wall sections Pu < 0.05 Ag f
for
walls within the bays between the frame columns.
c
geometrically unsymmetrical wall sections, and
See Figure 7-8 for details of shear walls with
either
boundary
elements.
Note
that
the
vertical
reinforcement in the boundary zones in Figure 7-8 is
2. Mu/Vu lw < 1.0
extended to be developed above and below the
prescribed limit of the boundary zones.
or
(d)
When boundaries are not required,
'
3. Vu < 3 Acv
f
and Mu/Vu lw < 3.0
c
special reinforced concrete shear walls shall comply
with Section 21.6 of ACI 318, as modified by the
f e' / 4 where:
applicable provisions of Section 9.1.1.13 of FEMA
The metric equivalent is vu ≤ Acv
302.
Pu = 1.2D+0.5L + E, kips (kN).
(4) Acceptance criteria.
Ag = gross area of the wall, in2 (mm2).
(a) Response modification factors, R, for
Performance Objective 1A are provided in Table 7-1.
Mu = required moment strength, kip-in (kN-
m).
(b) Modification factors, m, for enhanced
performance objectives are provided in Table 7-2 for
Vu = required shear strength, kips (kN).
components controlled by flexure, and in Table 7-3
for components controlled by shear.
lw = horizontal length of wall, in (mm).
Acv = net area of wall bounded by the web
thickness and length of section in2 (mm2).
(b) Design and detailing of boundary zones
shall be in accordance with the provisions of ACI
318, as modified by Section 9.1.1.13 of FEMA 302.
7-20
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