I, of the corner pier is 1.5 times that of a rectangular
which typical frame action predominates. Openings
pier; for other I-values, the bending portion of the
commonly occur in regularly spaced vertical rows
throughout the height of the wall, and the connection
deflection would be proportional.
The deflections
shown on the charts are for a horizontal load, P, of
between the wall sections is provided by either
connecting beams (or spandrels) which form a part of
1,000,000 pounds.
The deflections shown on the
the wall, or floor slabs, or a combination of both. If
charts are reasonably accurate. The formulas written
the openings do not line up vertically and/or
on the curves can be used to check the results;
horizontally, the complexity of the analysis is greatly
however, the charts will give no better results than
increased. In most cases, a rigorous analysis of a
the assumptions made in the shear wall analysis. For
wall with openings is not required. "Strut and Tie"
instance, the point of contraflexure of a vertical pier
procedures that depict shear walls as consisting of
may not be in the center of the pier height. In some
compression struts and tension ties are useful tools
cases, the point of contraflexure may be selected by
for the evaluation of shear walls with openings (see
judgment and an interpolation made between the
Paulay and Priestley, 1992). In the design of a wall
cantilever and fixed conditions.
with openings, the deformations must be visualized
in order to establish some approximate method for
(c) Foundation effects. The rotation at the
analyzing the stress distribution to the wall. Figures
foundation can greatly influence the overall rigidity
7-3 and 7-4 give some visual descriptions of such
of a shear wall because of the very rigid nature of the
deformations.
The major points that must be
shear wall itself; however, the rotational influence on
considered are the lengthening and shortening of the
relative rigidities of walls for purposes of horizontal
extreme sides (boundaries) due to deep beam action,
force distribution may not be as significant.
the stress concentration at the corner junctions of the
Considering the complexities of soil behavior, a
horizontal
and
vertical
components
between
quantitative evaluation of the foundation rotation is
openings, and the shear and diagonal tension in both
generally not practical, but a qualitative evaluation
the horizontal and vertical components.
will be provided.
(a) Relative rigidities of piers and spandrels.
(d) Framework effects. The relative rigidity
The ease of methods of analysis for walls with
of concrete or unit masonry walls with nominal
openings is greatly dependent on the relative
openings is usually much greater than that of the
rigidities of the piers and the spandrels, as well as the
building framework; therefore, the walls tend to resist
general geometry of the building. Figure 7-3 shows
essentially all or a major part of the lateral force.
two extreme examples of relative rigidities of exterior
walls of a building. In Figure 7-3A, the piers are
(2) Effect of openings. The effect of openings
very rigid and the spandrels are very flexible.
on the ability of shear walls to resist lateral forces
Assuming a rigid base, the shear walls act as vertical
must be considered. If openings are very small, their
effect on the overall state of stress in a shear wall is
minor.
Large openings have a more pronounced
effect, and if large enough, result in a system in
7-11
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