MCE = Expected moment capacity of the
by flexure, are evaluated as shown in Figure 6-5 for
beam or column with the design axial load and Fy for
beams in moment frames.
Coupling beams
the reinforcement equal to Fye.
controlled by shear are evaluated as indicated above
for walls controlled by shear, and the acceptance
d =
Depth of the beam or column, in.
criteria are tabulated in Table 7-5.
(mm).
4. Reinforced masonry shear walls. The
Ec = Elastic modulus of the concrete, ksi
acceptance criteria for these shear walls, tabulated in
(kPa).
Table 7-9, are provided in terms of drift ratios, ) /h,
as indicated in Figure 6-2b. Acceptance criteria for
Ig = Gross moment of inertia of the beam of
coupling beams for reinforced masonry walls are
column, in4 (mm4).
similar to criteria for coupling beams in reinforced
(Note that in Equation 6-11, the yield curvature, Ny,
concrete shear walls described in Paragraph iii
is calculated with Ig/2 and the plastic hinge length is
above.
assumed to be d/2.)
(c)
Force-controlled actions. Structural
components shall have lower-bound strengths, QCL,
3. Reinforced concrete shear walls.
not less than the required strength, QUF, from the
i.
Controlled by flexure.
For shear
appropriate combinations of seismic and gravity load
walls in which the vertical reinforcement is expected
effects. Lower-bound strengths, QCL, are defined in
to yield in flexure prior to the wall exceeding its
Paragraph 6-3a(3)b and in Chapters 7 through 10.
shear capacity, the acceptance criteria in Table 7-4
are provided in terms of the plastic rotation, 2 , as
(d). Reanalysis. The results of the analysis
indicated in Figure 6-4 and are similar to that for
must be carefully monitored to determine whether
concrete moment-resisting frames in Paragraph 2
any of the structural components have exceeded the
above with the depth, d, in Equation 6-11 to be
deformation limits indicated in Chapters 7 through
replaced by the length of the wall.
10 for the desired performance objectives. Minor
exceedance (i.e., 10 to 15 percent) of the deformation
ii.
Controlled by shear.
For shear
limits in a limited number of components may be
walls when the shear capacity is attained prior to
acceptable if it can be demonstrated that the
flexural yielding of the reinforcement, the tabulated
additional deformation does not have an adverse
acceptance criteria values in Table 7-5 represent
effect on the performance of the structure. All other
allowable values of the interstory drift ratio, ) /h,
components with excessive deformations should be
with reference to Figure 6-2b, and it is not necessary
strengthened to meet the acceptance criteria. If the
to determine ) y.
revised member sizes for the components are
significant, a reanalysis may be required to confirm
iii. Coupling beams. The acceptance
an acceptable response. Similarly, if the results of
criteria in Table 7-4, for coupling beams controlled
6 - 12
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