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 (a) Joint reinforced masonry construction consists of single or
multiple wythe walls and utilizes either hollow or solid masonry units. The
joint reinforced wall construction utilizes commercially available cold
drawn wire assemblies (see Figure 53), which are placed in the bed joints
between the rows of the masonry units. Two types of reinforcement are
available; truss and ladder types. The truss reinforcement provides the
more rigid system and, therefore, is recommended for use in blast resistance
structures. In the event that double wythes are used, each wythe must be
reinforced independently. The wythes must also be tied together using wire
ties. Joint reinforced masonry construction is generally used in
combination with flexible type supports. The cells of the units located at
the wall supports must be filled with grout. Typical joint reinforced
masonry construction is illustrated in Figure 54.
(b) Combined joint and cell reinforcement masonry construction
consists of single wythe walls which utilize both horizontal and vertical
reinforcement. The horizontal reinforcement may consist either of the joint
reinforcement previously discussed or reinforcing bars. Where reinforcing
bars are used, special masonry units are used which permit the reinforcement
to sit below the joint (Figure 55). The vertical reinforcement consists of
reinforcing bars which are positioned in one or more of the masonry units
cells. All cells, which contain reinforcing bars, must be filled with
grout. Depending on the amount of reinforcement used, this type of
construction may be used with either the flexible or rigid type support
systems.
(c) Non-reinforced masonry construction consists of single wythe
of hollow or solid masonry units. This type of construction does not
utilize reinforcement for strength but solely relies on the arching action
of the masonry units formed by the wall deflection and support resistance
(Figure 55). This form of construction is utilized with the rigid type
support system and, in particular, the shear wall and slab construction
system.
b.
Design Criteria for Reinforced Masonry Walls
(1) Static Capacity of Reinforced Masonry Units. Figure 56
illustrates typical shapes and sizes of concrete masonry units which are
commercially available. Hollow masonry units shall conform to ASTM C90,
Grade N. This grade is recommended for use in exterior below and above
grade and for interior walls. The minimum dimensions of the components of
hollow masonry units are given in Table 27.
(a) The specific compressive strength (f'm) for concrete
masonry units may be taken as:
Type of Unit
Ultimate Strength (f'm)
Hollow Units
1350
psi
Hollow Units filled with grout
1500
psi
Solid Units
1800
psi
while the modulus of elasticity, Em, of masonry units is equal to:
EQUATION:
Em =1000 f'm
(125)
2.08-200
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