Page 124 - Design of Reinforced Masonry Structures

3.18 CHAPTER THREE

TABLE 3.5 Allowable Stresses in Steel Reinforcement (Source: Concrete Reinforcing Steel Institute.)

Minimum tensile Minimum yield Allowable stress in
2
Grade of steel strength f u , lb/in. 2 stress f y , lb/in. tension, lb/in. 2
40 70,000 40,000 0.5f y = 20,000
50 80,000 50,000 0.4f = 20,000
y
60 90,000 60,000 0.4f = 24,000
y
75 100,000 75,000 Not listed
Wire joint 30,000
reinforcement

TABLE 3.6 Minimum Inside Diameters of Bend for Reinforcing Bars

Grade of steel Minimum inside
reinforcement Bar No. diameter
40 3 through 7 5 bar diameters
50 or 60 3 through 8 6 bar diameters
50 or 60 9, 10, and 11 8 bar diameters

of bend is referenced to the inside of the bars as it is easier to measure than the radius
of the bend. The primary consideration for these limitations is the feasibility of bending
without breakage.
Both 2009 IBC and MSJC-08 codes permit use of steel reinforcing bars conforming to
the following ASTM designations, which specify certain chemical and mechanical proper-
ties, and dimensions:
1. ASTM A82/A82M-05a: Standard Specification for Steel Wire, Plain, for Concrete
Reinforcement [3.26]. This specification covers most commonly used and commer-
cially available plain bars in sizes up to ¾ in. The ¼-in. bar, the smallest diameter bar
that is permitted by codes for use as ties in masonry members is a plain bar manufac-
tured to this specification. The ultimate strength of the ¼-in. plain bar is 80 ksi and the
yield strength is 70 ksi.
2. ASTM A615/A615M-5b: Standard Specification for Deformed and Plain Billet-Steel
Bars for Concrete Reinforcement [3.27]. This specification covers most commonly used
and commercially available bar sizes—sizes 3 through 18 in Grade 60, sizes 3 through
6 in Grade 40, and sizes 6 to 18 in Grade 75.

3. ASTM A706/A706M-05: Standard Specification for Low-Alloy Steel Deformed Bars
for Concrete Reinforcement [3.28]. This specification covers bars intended for special
applications where weldability, bendability, or ductility is important.
4. ASTM A767/A767M-05: Specification for Zinc-Coated (Galvanized) Steel Bars for
Concrete Reinforcement [3.29]. The surface of these bars is coated with a layer of zinc
as a means to provide protection from corrosion. The bars are galvanized after their
fabrication. The specification covers requirements for the zinc-coating material, the
galvanizing process, the class or weight of coating, finish, and adherence of coating.
This specification has three supplementary requirements (S1, S2, and S3), which deal
with condition assessment and special requirements and apply only when specified by
the purchasers.