TM 5-809-12/AFM 88-3, Chap. 15
tc ' 10
' 9 inches
from figure 3-1, minimum tc = h h1; tc = 7+ 2 = 9 inches.
Example 2: Thickened floor slab design for exterior wall.
Problem. The thickened concrete floor slab supporting an 8 inch exterior load bearing wall
weighing 1,000 pounds per linear foot should be designed.
Floor slab data
Thickness = 4 inches
Flexural strength = 600 pounds per square inch
Modulus of subgrade reaction k = 200 pounds per cubic inch
Solution. Table 3-3 should be entered using 600 pounds per square inch and wall load, p =
1,000 pounds per linear foot. Thickness t should be adjusted based on modulus of subgrade reaction, k =
200 pounds per cubic inch.
te ' 10
For thickened slab configuration, see table 3-3.
For other practical considerations, i.e., frost line, erosion etc., the thickness, te, may be increased.
Example 3: Reinforced concrete slab.
Problem. It is decided that the 7-inch floor slab in Example 1 should be reduced to 6 inches by
reinforcing the slab using 60,000-pounds per square inch yield strength steel reinforcement. The percent
reinforcement required for the 6-inch slab should be determined.
Solution. From figure 5-4, a straight line should be drawn between h = 7 inches and hr = 6 inches
and extend line to S. This should read S = 0.13 percent.
Example 4: Concrete slab Thickness for tracked vehicle.
Problem. The floor slab thickness h, should be determined for a tank repair shop. The largest
tank has a gross weight of 60 kips, Traffic is limited to 40 vehicles per day.
Concrete flexural strength = 700 pounds per square inch
Modulus of subgrade reaction, k = 100 pounds per cubic inch
on 60 kips gross weight, equivalent forklift truck category
II is selected from
second tabulation in paragraph 3-2. From first tabulation in paragraph 3-2 for category II, forklift truck axle
load is 10 to 15 kips. Table 5-1 is entered using 15 kips. Loaded at a frequency of 100 operation per day, the
design index is 7. Figure 5-1 is entered using concrete flexure strength = 700 pounds per square inch, k = 100
pounds per cubic inch and DI = 7, slab thickness, h = 6.6 inches, or if rounded, 7 inches.