Post on 02-Apr-2018
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Federal Aviation
Administration RigidPavement Design Method
Part I
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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).
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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
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Dense Liquid Foundation
k = Modulus of Subgrade Reaction
Assumes:Plate in Contact
w/ Subgrade
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Aircraft Considerations
LoadPavement design based on
maximum anticipated takeoff
weight
Assumes 95% of the load on main
gear
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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)
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Design Inputs
Concrete flexural strength Supporting modulus
Design aircraft gross weightAnnual departures of the design
aircraft
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Design Aircraft & Departures
Determined as before
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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
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Concrete Flexural Strength
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Concrete Flexural Strength
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Supporting Modulus
k value Spring constant of the
supporting material
Indicative of the support material
bearing capacity
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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)
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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
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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)
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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)
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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
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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
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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
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Traffic Distribution
Full-depth design thickness requiredwhere departing aircraft use
pavement
Aprons
Holding areas
Center of runways and taxiways
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Traffic Distribution
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
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Traffic Distribution
Thinning of pavement sectionsapplies only to the concrete slab, not
the subbase