Page 444 - Design of Reinforced Masonry Structures

7.6 CHAPTER SEVEN

be considered fixed at both top and bottom (similar to a fixed-ended beam). It is common
practice to consider shear walls in one- or two-story buildings as cantilevered, whereas in
a multistory building, the segments of the walls between various stories are considered to
be fixed both at the top and bottom.
While the discussion in this chapter is focused on the design of wall elements as shear
walls (i.e., on their in-plane resistance), it is noted that these walls, as components of a bear-
ing wall system, must posses adequate strength to resist the following forces:
1. Gravity loads from diaphragms (roofs or floors), which may be applied eccentrically
2. Lateral or in-plane loads received from the diaphragms
3. Out-of-plane loads (due to wind or earthquake) acting perpendicular to it

Loads in cases 2 and 3 are assumed not to act simultaneously.

7.3 TYPES OF SHEAR WALLS

Shear walls can be variously classified depending on the objective. They can be classified
as load-bearing or nonload-bearing, depending on whether they carry gravity loads also in
addition to lateral load. They can be classified based on the type of masonry and construc-
tion used, for example, brick or concrete, reinforced and unreinforced, single or multiple
wythe, single story or multistory, solid or perforated, rectangular or flanged, cantilever or
coupled, etc. Most commonly used shear walls have rectangular or flanged configuration.
Several types of shear walls are shown in Fig. 7.8.

Pier Spandrel
Window
Door Pier
opening opening

Solid Wall with Solid cantilever Perforated Coupled
wall openings wall wall wall
(a) (b)
FIGURE 7.8 Types of shear walls: (a) single story, (b) multistory [7.1].

Efficiency of shear walls is best described in terms of their rigidities (or stiffnesses).

As such, solid shear walls are the most efficient and, therefore, highly desirable. Often
shear walls would have opening in them as a matter of functional necessity (e.g., doors
and windows); such walls are sometimes referred to as perforated (i.e., wall with open-
ings). The portion of a shear wall between two adjacent openings is called a pier, whereas,
the segment of shear wall above the adjacent openings is called a spandrel or a beam. A
shear wall with openings can be analyzed as a frame composed of short stiff wall seg-
ments (also called piers). In many shear walls, a regular pattern of windows or doors, or
both, is required for functional considerations. In such cases, the walls between the open-
ings may be interconnected by spandrels (or beams), resulting in coupled shear walls.
The connecting elements (i.e., beams) between coupled shear walls typically require
horizontal and vertical reinforcement to transfer shear from one segment of the wall to the
other (Fig. 7.9). When the connecting elements are incapable of transferring shear from