Page 353 - Design of Reinforced Masonry Structures

WALLS UNDER GRAVITY AND TRANSVERSE LOADS 6.5

special precautions may be required when a single-wythe wall is used on the exterior of
a building. The thickness t of a single-wythe wall is equal to the width of the masonry
unit used, which can be solid, cored, or hollow.
4. Walls can be solid as constructed from solid bricks of concrete or clay or from hollow
masonry units, which can be single- or multiple-wythe. When constructed from hollow
masonry units, masonry walls can be partially or fully grouted. Before the development
of modern masonry, solid wall consisted of two wythes of brickwork or stonework, with
the space in-between filled with rubble or concrete. In modern masonry construction
practice, solid walls are constructed with two or more closely spaced wythes. The inter-
3
3
vening space between the wythes, generally, / 8 to / 4 in. wide, is filled with mortar or
grout (Fig. 6.5) and referred to as the collar joint. In some cases, the intervening space
may be 2 to 3 in. wide, referred to as the cavity, which is later filled with grout forming
a grouted wall. Such walls are called the cavity walls. It important to construct two-
wythe walls in such a manner that sufficient shear strength is developed at the interface,
and the two separate wythes act integrally. This is accomplished by providing sufficient
number of headers and metal ties that tie the two wythes together. These walls can be
reinforced both horizontally and vertically. In cavity walls, it is common practice to
provide horizontal and vertical reinforcement in the grouted cavity. In two-wythe walls
with collar joints, the horizontal reinforcement is provided in mortar joints and vertical
in the collar joints. Because of their greater thickness, the two-wythe walls offer greater
strength and moisture-penetration resistance relative to a single-wythe wall.
When walls are made from hollow masonry units, all or only a few selected cells may
be grouted depending on the design requirements. When all the cells are grouted, a wall
is rendered solid and referred to as a solid or fully grouted wall. Grouting only a few
selected cells renders a wall partially grouted wall. Grouted cells might have reinforcing
bars passing through them; such a wall is called a reinforced masonry wall. Reinforced
masonry walls are usually single-wythe walls, unless two-wythe walls are used for some
specific purposes.
5. Masonry walls can be built without any reinforcement, resulting in unreinforced masonry
walls (not discussed in this book). Masonry walls built with reinforcement are called
reinforced masonry walls. Both solid and single-wythe walls can be reinforced. Wall
reinforcement can be horizontal or vertical. Horizontal reinforcement can be placed
in bed joints, in collar joints, or in the grouted cavity between the wythes (Fig. 6.5).
Vertical reinforcement can be provided in the grouted cores of hollow units or in the grouted
pockets of walls constructed from solid units (Fig 6.6a and b). In single-wythe walls built

FIGURE 6.5 Cavity walls. (Courtesy: BIA.)