lecture 21 faa rigid

PAVEMENT DESIGN

AND ANALYSIS

(CE-860)

LEC-21

Fall Semester 2015

Dr. Arshad Hussain

arshad_nit@yahoo.com , Office Room#111, Tel: 05190854163, Cell: 03419756251

National Institute of Transportation (NIT)

School of Civil & Environmental Engineering (SCEE)

National University of Science and Technology (NUST)

NUST Campus, Sector H-12, Islamabad

RIGID AIRPORT PAVEMENT DESIGN

FAA DESIGN METHOD

FAA DESIGN PROCEDURE

1. Design Inputs

a. Concrete flexural strength (90 days)

b. Modulus of subgrade reaction (k)

c. Gross weight of design aircraft

d. Equivalent annual departure of design

aircraft

FAA DESIGN PROCEDURE

2. Thickness Selection

a. Separate design curves for single, dual and

dual tandem gear assembly and separate

wide body aircraft.

b. Design curves indicate thickness of PCC

slab only and this thickness ‘ T ’ is the

critical thickness.

FAA DESIGN PROCEDURE

3. Subbase Requirements

a. A minimum thickness of 4 inches of

subbase required except as shown in

Table 3-10 conditions where no subbase

is required.

Soil

Classifi

cation

Good Drainage Poor Drainage

No

FrostFrost

No

FrostFrost

GW x x x x

GP x x x

GM x

GC x

SW x

x indicates conditions where no subbase is required

TABLE 3-10

FAA DESIGN PROCEDURE

b. Subbase thickness in excess of 4 inches

can be used to decrease the required

thickness, if economical.

c. Stabilized subbase is required if aircraft

weighing more than 100,000 lbs is

present in the mix.

Conversions for different gear types

FAA DESIGN PROCEDURE

4. Subgrade Compaction Requirement

a. For Cohesive Soils

Must be compacted to 90 % maximum

density for fill (ASTM D 698)

Top 6 inches must be compacted to 90%

maximum density in cut section.

FAA DESIGN PROCEDURE

b. For Cohesionless Soils

In fill section top 6 inches must be compacted

to 100 % maximum dry density and remainder

95 %.

In cut section Top 6 inches must be compacted

to 100% maximum density and next 18 inches

to 95 %.

FAA DESIGN PROCEDURE

5. Determination of k

a. k should be assigned to material directly

beneath concrete slab.

b. Determine k for subgrade soil and use curve

to improve k values for given subbase material

& thickness Table 2-3

c. Use Fig. 2-4 to improve k for untreated

subbase.

Effect of subbase on k (well graded crushed aggregate)

Effect of subbase on k (bank-run sand & gravel)

FAA DESIGN PROCEDURE

Use Fig. 3-16 to improve k for stabilized

subbase (applicable to cement or

bituminous treated subbase.

FAA DESIGN PROCEDURE

6. Critical & non-critical areas

Fig. 3-1

a. Design curves give T, the critical thickness

b. 0.9T thickness for non-critical areas

applicable to concrete slab.

c. Variable thickness section & thinned edge

section reduction factors (0.7 T) applies to

slab thickness.

FAA DESIGN PROCEDURE

d. Subbase thickness must be adjusted to

provide continuous drainage at subgrade.

High TrafficVolume

Provide additional thickness for

departures in excess of 25,000 according

to Table 3-5.

Pavement Thickness for Higher

Departure Levels

For annual departures in excess of 25,000 the total

pavement thickness should be increased as shown below:

________________________________________

Annual departure Per cent of 25000

level departure thickness

________________________________________

50,000 104

100,000 108

150,000 110

200,000 112

________________________________________

DESIGN EXAMPLE

DESIGN EXAMPLE (Cont)

Assumed Material Properties

FAA Software for Rigid

R805FAA For Rigid Pavement Design