Masonry Magazine March 1967 Page. 34
RELATIONSHIP OF COMPRESSIVE STRENGTH OF MASONRY TO COMPRESSIVE STRENGTH OF MASONRY UNITS
Based on the Building Code Requirements for Reinforced Masonry (American Standard A41.2-1960). Tests to determine the compressive strength of the units should be conducted in accordance with ASTM C140, Standard Methods of Sampling and Testing Concrete Masonry Units.
TABLE 2
(Gross area for solid-unit masonry and net area for hollow-unit masonry)
| Compressive Strength of Units t. psi | Assumed Compressive Strength of Masonry, fim. psi |
|---|---|
| over 1000 to 1500 | 900 to 1150 |
| over 1500 to 2500 | 1151 to 1550 |
| over 2500 to 4000 | 1551 to 2000 |
| over 4000 to 6000 | 2001 to 2400 |
| over 6000 to 8000 | 2401 to 2700 |
| over 8000 to 10,000 | 2701 to 2900 |
| over 10,000 to 12,000 | 2901 to 3000 |
| over 12,000 | 3000 |
TABLE 3
BASIC ALLOWABLE STRESSES FOR CONCRETE MASONRY
| | Masonry Construction of: |
|---|---|
| | Hollow Units | Solid Units | Grouted or Filled-Cell Units |
| Basic Allowable Stresses | Type M or S Mortar | Type N Mortar | Type M or S Mortar | Type N Mortar | Type M or S Mortar |
| Shear, psi | 34 | 23* | 34 | 23 | 34 |
| Tension in Flexure, psi | 23* | 16* | 39 | 27 | 39 |
| Compression for Unit Strength, psi, of: | 700 | 95 | 90 | 95 | 90 | 200 |
| | 1000 | 135 | 125 | 135 | 125 | 235 |
| | 1200 | 160 | 150 | 160 | 150 | 265 |
| | 1500 | 200 | 185 | 200 | 185 | 300 |
| | 1800 | 240 | 225 | 240 | 225 | 330 |
| | 2500 | 330 | 315 | 330 | 315 | 400 |
| | 3500 | 460 | 440 | 460 | 440 | 500 |
Net mortar bedded area.
TABLE 4
| | Slenderness | Eccentricity of Vertical Load: |
|---|---|---|
| CORRECTION FACTORS FOR WALL SLENDERNESS AND ECCENTRICITY OF LOADING | Ratio, H/T | 0 | t/6 | 1/3 |
| | 6 | 1.28 | 1.12 | 0.96 |
| | 8 | 1.24 | 1.06 | 0.88 |
| | 10 | 1.20 | 1.00 | 0.80 |
| | 12 | 1.16 | 0.94 | 0.72 |
| | 14 | 1.12 | 0.88 | 0.64 |
| | 16 | 1.08 | 0.82 | 0.56 |
| | 18 | 1.04 | 0.76 | 0.48 |
| | 20 | 1.00 | 0.70 | 0.40 |
Intermediate valves may be interpolated.
NATIONAL CONCRETE MASONRY ASSOCIATION
2009 14th Street North Arlington, Virginia 22201