Page 522 - Design of Reinforced Masonry Structures

7.84 CHAPTER SEVEN

as SFRS elements in Seismic Design Category A and B structures. Although classified as
unreinforced, these walls are subject to certain reinforcement detailing (both vertical and
horizontal) requirements (MSJC-08 Section 1.17.3.2.3.1) as follows:
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1. Vertical reinforcement of 0.2 in. in cross-sectional area at
(a) All corners
(b) Within 16 in. of each openings
(c) Within 8 in. of each side of movement joints
(d) Within 8 in. of ends of wall
(e) At a maximum spacing of 10 ft
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2. Horizontal reinforcement of at least 0.2 in. in cross-sectional area of bond beam rein-
forcement spaced not more than 10 ft on center, or at least two wires of W 1.7 joint
reinforcement spaced not more than 16 in. at
(a) Top and bottom wall openings extending at least 24-in. or 40-bar diameters (which-
ever is greater) past openings
(b) Continuously at structurally connected roofs and floors
(c) Within 16 in. of top of walls

Ordinary reinforced masonry shear walls are shear walls in which the tensile strength
of masonry is neglected and tension at any cross section is assumed to be resisted by the
reinforcement. For seismic design, they are permitted as parts of SFRS in Seismic Design
Category A, B, and C structures (limited to a height of 160 ft in Seismic Design Category C);
they are assigned an R value of 2 and an overstrength factor W = 2.5. They are designed to
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comply with requirements of MSJC-08 Sections 2.3 and 3.3 for ASD and SD, respectively.
Additionally, these walls must also comply with detailing requirements for detailed plain
masonry shear walls specified above (MSJC-08 Section 1.17.3.2.3.1).
Minimum reinforcement requirements for detailed plain and ordinary reinforced
masonry shear walls are shown in Fig. 7.31.
Intermediate reinforced masonry shear walls are designed to comply with requirements
of MSJC-08 Sections 2.3 and 3.3 for ASD and SD, respectively. They must be provided
with detailing requirements for detailed plain masonry shear walls (described above) except

FIGURE 7.31 Minimum detailing requirements for detailed plain and ordinary reinforced masonry shear
walls [7.16]. (Courtesy: CMACN.)