UFC 3-260-03
15 Apr 01
The evaluation is based on the thickness of the pavement in the center 23-meter (75-foot) width of the
runway and the runway is divided into two traffic areas. The first 305 meters (1,000 feet) at the ends are
primary traffic areas and the runway interior is a secondary traffic area. The evaluation will be made using
figure 6-55. Enter the figure with the given parameters as shown by the arrows and read an allowable
gross weight of 27,700 kilograms (61,000 pounds) for the primary traffic area and 29,500 kilograms
(65,000 pounds) for the secondary traffic area.
6. REINFORCED CONCRETE PAVEMENT. The data required for the evaluation of reinforced con-
crete pavements and the selection of representative physical property values are essentially the same as
those for plain concrete pavements presented in chapter 3, except that the percent steel is also required.
a. Reinforcing Steel. The reinforcing steel in a reinforced concrete pavement will normally be
located at or above the neutral axis of the pavement section. If the steel is below the neutral axis, it would
affect the determination of the flexural strength and the static modulus of elasticity in flexure. Therefore,
when the reinforcing steel falls below the neutral axis in a test beam, the beam should be turned over and
tested with the reinforcing steel above the neutral axis. The splitting tensile tests cannot be performed on
a core of reinforced rigid pavement if any of the reinforcing steel is present in the core to be tested. It may
be possible to obtain a core that contains none of the reinforcing steel, in which case the splitting tensile
tests could be performed. However, if the pavement thickness is great enough, it may be possible to saw
the core just below the reinforcing steel and perform the splitting tensile test on the lower, nonreinforced
portion.
b. Method of Evaluation. Reinforced concrete pavements may be found on grade (single slab), as
a part of an overlay system, or over stabilized layers. In either case, for Army and Air Force evaluations
the thickness of the reinforced concrete pavement is converted to an equivalent thickness of plain con-
crete pavement, and the evaluation is made in the same manner as plain concrete. However, for Navy
and Marine Corps pavements, the thickness of reinforced concrete is treated as if it was not reinforced
and is evaluated as a plain concrete pavement.
(1) The first step in the evaluation of an Army or Air Force reinforced concrete pavement is to
compute the thickness of a plain concrete pavement (equivalent thickness) having the same load-carrying
capacity as the reinforced concrete pavement. This equivalent thickness hE is determined from fig-
ure 6-60, using the known thickness of the reinforced concrete pavement hr and the percentage of steel
reinforcement S per foot of pavement cross-sectional area. The percentage of steel is computed from
equation 6-2:
As
S'
100
(eq 6-2)
Ap
where
As = cross-sectional area of the reinforcing steel per foot of pavement width or length, square
millimeters (square inches)
Ap = cross-sectional area of pavement per foot of pavement width or length, square
millimeters (square inches)
It is necessary to compute the percent steel in both the longitudinal and transverse directions. Normally it
will be the same in both directions, but if there is a difference, the smaller value will be used. Next, enter
figure 6-60 with the known value of hr . Make a vertical projection and extend it until it intersects the
diagonal line representing the computed value of S . Then make a horizontal projection to the left until it
6-6
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