Thickened floor slab design for exterior wall.

TM 5-809-12/AFM 88-3, Chap. 15

100

tc ' 10

' 9 inches

200

from figure 3-1, minimum tc = h h1; tc = 7+ 2 = 9 inches.

C-2.

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.

100

' 8.7

te ' 10

200

For thickened slab configuration, see table 3-3.

Note:

For other practical considerations, i.e., frost line, erosion etc., the thickness, te, may be increased.

C-3.

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.

C-4.

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.

Material Properties:

Concrete flexural strength = 700 pounds per square inch

Modulus of subgrade reaction, k = 100 pounds per cubic inch

Solution. Based 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.

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