Faa Rigid Design

7/27/2019 Faa Rigid Design

1/26

Federal Aviation

Administration RigidPavement Design Method

Part I


2/26

Rigid Pavements

Portland cement concrete placed ona granular or treated subbase course

that is supported on a compacted

subgrade (AC 150/5320-6D, Change3, paragraph 324).


3/26

Rigid Pavement Design

Series of design curves based on theWestergaard edge loading analysis

Design curves depend on gear

configurationDesign curves & optional design

curves Curves provide slab thickness only

Curves based on 20 year design life


4/26

Dense Liquid Foundation

k = Modulus of Subgrade Reaction

Assumes:Plate in Contact

w/ Subgrade


5/26

Aircraft Considerations

LoadPavement design based on

maximum anticipated takeoff

weight

Assumes 95% of the load on main

gear


6/26

Aircraft Considerations

Landing gear type and geometry Single

Dual

Dual tandem

Wide body aircraft (B-747)

Tire pressure (75-200 psi) Traffic volume (annual departures by

aircraft type)


7/26

Design Inputs

Concrete flexural strength Supporting modulus

Design aircraft gross weightAnnual departures of the design

aircraft


8/26

Design Aircraft & Departures

Determined as before


9/26

Concrete Flexural Strength

Measured using ASTM C78 Value should be based on age and

strength of concrete at the time the

pavement will be opened to traffic


10/26



11/26



12/26

Supporting Modulus

k value Spring constant of the

supporting material

Indicative of the support material

bearing capacity


13/26

k Value

The k value should be assigned tothe material directly beneath theconcrete pavement

Establish a k value for the subgrade,then correct it to account for thesubbase

A minimum of 4 in. of subbase isgenerally required (paragraph 326)


14/26

Subgrade k Value

Should be established on subgradeprepared to specification

Plate load test (AASHTO T222)

Values from Table 2-3 may be used

Only approximate

Use engineering judgment


15/26


16/26

Subbase k Value

Can be assigned using Table 2-4 Upper graph used

Subbase of composed of well-graded, crushed aggregate such as

P-209

Lower graph used

Bank run sand & grave (P-154)


17/26


18/26

Stabilized Subbase k Value

k value will increase when subbaseis stabilized

Figure 3-16 can be used to determine

likely increase Figure is applicable to:

Cement stabilized (P-304)Econocrete (P-306)

Bituminous stabilized (P-401)


19/26


20/26

Frost Protection

Complete frost protection Limited subgrade frost penetration

65% of frost penetration depth iscomposed of non-frost susceptible

material

Reduced subgrade strength

Increase pavement thickness


21/26


22/26

Frost Protection

Option 1 (Complete)

Used w/ FG-3 and FG-4 soils

Areas where no heave can be

tolerated Option 2 (Reduced)

FG-4, unless option 1 is required

FG-1, FG-2, FG-3 where minorheave can be tolerated


23/26

Frost Protection

Option 3 FG-1, FG-2, FG-3 where some

degree of heave is permissible

Also, with these three soils in

areas subject to slow traffic where

heave can be tolerated


24/26

Traffic Distribution

Full-depth design thickness requiredwhere departing aircraft use

pavement

Aprons

Holding areas

Center of runways and taxiways


25/26


90% of design thickness requiredwhere arriving aircraft will usepavement

High speed turnouts 70% of design thickness required

where pavement use is unlikely

Outer edges of runways andtaxiways


26/26


Thinning of pavement sectionsapplies only to the concrete slab, not

the subbase

Documents

Faa Rigid Design