TM 5-809-1/AFM 88-3, Chap. 15
CHAPTER 5
DESIGN PROCEDURE
5-1. General.
which expresses varying axle loads and traffic
volume in terms of relative severity. The DI ranges
Once the floor-slab design requirements have been
from 1 to 10 with the higher number indicating a
established, i.e., the type of loadings, including wall
more severe design requirement. The basic loading
loads and both stationary live and moving live loads,
described above was used to assign and rank the
the requirements are translated into meaningful
Dl*s. More information concerning the DI can be
design data. These design data are then compared
found in TM 5-822-6/AFM 88-7, Chap. 1. Table 5-
with the existing condition data, and a floor slab
1 shows the DI*s for various traffic volumes. Thick-
design is evolved. The design procedure covers sub-
ness requirements for floor slabs which contain only
grade conditions, steel reinforcing, and various de-
temperature reinforcement for the ten DI*s are
tails such as jointing.
shown in figure 5-1. The floor-slab thickness
requirements are a function of concrete strength and
5-2. Floor slab loads.
subgrade modulus and DI. Larger forklifts having
a. Traffic loadings. In order to satisfy require-
axle loads greater than 25 kips are treated
ments of different types of vehicles and traffic vo-
separately. The required slab thickness for
lumes, all Category I, II, and III traffic has been
pavements designed for these loads are not
expressed in terms of equivalent operations of a
significantly affected by vehicles having axle loads
basic axle loading. The basic loading was assumed
less than 25 kips (trucks, cars, buses, and small
to be an 1 8,000-pound single-axle load with two
forklifts). These light loads are therefore ignored in
sets of dual wheels spaced 58-1/2 inches apart with
determining requirements for pavements carrying
13-1/2 inches between dual wheels. It should be
axle loads greater than 25 kips. The thickness
noted that the basic loading was arbitrarily selected
requirements for these loads are shown in figure 5-2.
to provide a reasonable spread in the loadings and
traffic volumes likely to be encountered under
normal conditions. A design index (DI) was devised
Table 5-1. Traffic categories for design index
Maximum Operations
Design
Per Day Over 25 Years
Load
Index
50
10-kip axle-load forklift truck
4
250
10-kip axle-load forklift truck
5
10
15-kip axle-load forklift truck
250
10-kip axle-load forklift truck
7
100
15-kip axle-load forklift truck
250
15-kip axle-load forklift truck
8
5
25-kip axle-load forklift truck
5-1
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