UFC 3-260-02

30 June 2001

CHAPTER 19

LAYER ELASTIC DESIGN OF RIGID PAVEMENTS

1. RIGID PAVEMENT DESIGN PRINCIPLES. The basic design principle for this design procedure is

to limit the tensile stresses in the Portland Cement Concrete (PCC) to levels that are sufficiently below

the flexural strength of the concrete such that failure occurs only after the pavement has sustained a

number of load repetitions. The tensile stress is modeled by the use of Burmister's solution for elastic

multilayered continua and calculated using the JULEA computer program. The computed tensile stress

divided by the concrete strength is the design parameter and is referred to as the design factor. This

parameter has been related to pavement performance through a study of test section data. To account

for mixed traffic, i.e., traffic producing stresses of varying magnitudes, the cumulative damage concept

based on Miner's hypothesis is employed. This procedure may be used as an option to the empirical

procedure for the design of new Navy pavements. The design procedure is illustrated in Figure 19-1 and

summarized as follows:

a. Select three or four concrete slab thicknesses and compute the maximum tensile stresses in the

slabs under the design aircraft load.

b. Based on the computed stresses, determine the allowable coverages Ni (Ni = Co for initial

cracking criteria or Ni = Cf for complete failure criteria) using Equations 19-1, 19-2, and 19-3 for each

thickness design.

c. Compute the damage for each design which is equal to the ratio of the design coverage ni to

the allowable coverage Ni , where i varies from 1 to the number of aircraft.

d. Select the proper slab thickness at a damage value of 1.0 from the relationship between

damage and slab thicknesses.

e. The selection of an unbound granular base or a stabilized base under the concrete slab is a

matter of engineering judgment depending on many factors such as cost, material availability, frost

penetration requirement, and subgrade swell potential. Subgrade soil may be stabilized to gain strength

or modified to increase its workability and reduce swell potential.

2. RIGID PAVEMENT RESPONSE MODEL. The pavement is assumed to be a multilayered

continuum with each layer being elastic, isotropic, and homogeneous. Each layer is to extend to infinity

in the horizontal direction and to have, except for the bottom layer, a finite thickness. The applied loads

to the pavement are considered as static circular and uniform over the contact area. The program

chosen for the analysis is JULEA computer code. This program was chosen because it provided

accurate computations and provisions for different degrees of bond between interfaces. Investigations

into modeling rigid pavements with this code have resulted in the performance criteria being developed

with the assumptions that the interface between the PCC slab and the supporting subgrade is

considered smooth with no bond; i.e., there is no frictional resistance at the interface and all other

interfaces are considered to be completely bonded. At a depth of 6 meters (20 feet), a very stiff bottom

layer is used to mitigate the assumption that the bottom layer extends to infinity. Figure 21-1 presents a

diagram for the design of pavements using the layered elastic analysis.

3. DESIGN PROCEDURE. Design of rigid pavements using the elastic layered procedure is initiated

by assuming a pavement section. The assumptions are the number of layers, type of materials, and

19-1

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