Masonry Magazine June 1973 Page. 33
5.2
1/3 =
9.62
3
STRESS
MAGRAM
5.62
= 3.33 in.
3
3.21 in.
Therefore e t/3
Determine (section 3.8.8.2.):
f-0.75 fF
For solid block and type S mortar
F₁ = 39 psi
fa (brick face) =n
P
2000
A
= (1.41)
133.5
21.2 psi (comp.)
f (brick face) = n ()=
(2000)(3.33)
(1.41)
(238)
39.4 psi (tension)
fm-0.75 f=39.4-0.75 (21.2) =
23.5 psi 39 psi.. OK
Combined Stress (brick face)
fa-f21.2-39.4=
-18.2 psi (tension)
Combined Stress (block face)
2000 + 2000(3.33)
=
133.5
202
15+3348 psi (comp.)
At blockbrick interface:
Combined Stress (block)
37.32
= fa-f=15
(2000)(3.33)
1051/0.8
10 psi (compression)
Combined Stress (brick)
= n (fa-f)
1.41(10)=14.1 psi (comp.)
Design Tables. "Non-reinforced Concrete Masonry Design Tables,"
a 400 page report published by NCMA in 1971, contains approximately 160 pages of design tables pertaining to ten different types of composite concrete masonry walls.
These composite walls range in thickness from 8 inches to 16 inches, and in all cases, the exterior wythe of the wall is assumed to be a 4-inch thick solid concrete brick and the interior wythe is assumed to be either hollow or solid units varying in thickness from 4 inches to 12 inches. Table 1 indicates allowable vertical loads (kips per foot of wall length) for an 8-inch composite wall of 4-inch concrete brick and 4-inch hollow concrete block assuming a masonry strength (f'm) of 2500 psi.
The previously mentioned report also contains design tables for other masonry strengths ranging from 1000 psi to 3500 psi. Additional design tables are also included for (1) allowable vertical loads (pounds per foot of wall length) governed by tension in the wall due to eccentricity of loading, and (2) maximum uniform lateral loads (pounds per square foot) on walls of various height and supporting different magnitudes of axial compressive load. Non-structural properties such as thermal and acoustical data and fire-resistance ratings are also given in the report for composite concrete masonry walls.
TABLE 1. ALLOWABLE LOAD, Kips Per Foot of Wall Length
CONSTRUCTION: 8-inch Composite Wall of 4-inch Concrete Brick and 4-inch Hollow Concrete Block
PRISM STRENGTH: 2500 pst
Wall Height.
Ft-In.
Virtual Eccentricity (e) in Inches
Axial
0.2 0.4 0.6
0.8 1.0 1.2
1.4
4-0
37.62 33.29 29.86
27.07 24.75
22.00 21.14 19.70
4-8
37.54 33.23 29.00
27.01 24.70
22.76 21.10 19.66
5-4
37.44
33.14 29.72
26.94 24.64
22.70 21.04
19.61
6-0
37.32
33.02 29.62
26.85 24.55
22.62 20.97 19.54
6-8
37.16 32.00 29.49
26.73 24.45
22.52 20,88 19.46
7-4
36.96 32.71 29.34
25.59 24.32 22.41 20.77 19.36
8-0
36.73
32.50 29.15
26.43 24.17
22.26 20.64 19.23
8-8
36.45
32.26 20.93
26.23 23.98
22.10 20.48 19.09
9-4
36.13 31.97 28.68 25.99 23.77 21.90 20.30 18.92
10-0
35.75 31.64 28.38 25.73 23.53 21.67 20.09 18.72
10-8
35.33 31.27 28.04 25.42
23.25 21.42 19.65 18.50
11-4
34.05 30.04 27.66 25.07
22.93 21.12 19.58 18.25
12-0
34.31 30.36 27.23 24.68
22.67 20.80 19.28 17.97
12-8
33.70 29.82 26.75 24.25
22.17 20.43 18.94 17.65
13-4
33.03 29.23 26.21 23.76 21.73 20.02 18.56 17.30
Mock