Repeat Problem 20-22, using the PCA design method, assuming the pavement has doweled joints and no concrete shoulders.

Question

What will be an ideal response?

Answer 1

First, determine the estimated ESALs:

2-axle (12,000 lb) single unit trucks:

ESAL = 2(0.4)(28.28)(24,000)(365)(0.40)

ESAL = 79.27 × 106

3-axle (16,000 lb) single unit trucks

ESAL = 3(0.1)(28.28)(24,000)(365)(0.40)

ESAL = 29.73 × 106

Subgrade k = 50 lb/in3

For 6 inch stabilized subbase, determine effective k from Table 20.22:

k = 230 lb/in3

Assume a slab 8 inches thick with doweled joints and no concrete shoulders.

From Table 20.23, obtain equivalent stress values and interpolate for k,

Equivalent stress = 242 – ((242 – 225) × (30 / 100)) = 236.9

Stress Ratio = 236.9 / 600 = 0.39

From Table 20.25, determine the erosion factor of 2.80

12,000(1.2) = 14,400

16,000(1.2) = 19,200



The 8 inch slab is adequate under fatigue analysis but not for the erosion criterion.

Assume a slab 8.5 inches thick with aggregate interlock joints and concrete shoulders.

From Table 20.25, determine the erosion factor of 2.72

12,000(1.2) = 14,400

16,000(1.2) = 19,200