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DOC 9157-ARf901 P a r t3
AmendmentBo
.
2 31/8/89 AMENDMENTNO.
2
TO TBEAERODROME
DESIGN
MANUALPART 3
PAVEMENTS
SECOND EDITION
-
1983Amendmen€
No,
2 includes guidance materialon
grooving runwayi n t e r s e c t i o n s and t h e c o n s t r u c t i m o f a s p h a l t i c o v e r l a y s . A l s o i n c l u d e d
are
updated data.an
ACRs f o r a i r c r a f t .R e p l a c e e x i s t i n g p a g e s
Cvii),
3--219 t o 3-224, 3-237 t o 3-249 and 3-339 t o3-346
by
t h e a t t a c h e dnew
pages.Remove
exiatfng
pages 3-347 and 3-348.R e c o r a t h e e n t r y o f t h i s amendment
on
page( i i ) .
1.
2.
3 . 5 .
T r a n s m i t t a l N o t e DOC 9157-Ah/901 P a r t 3 Amendment No. 1 25/10/85 AMENDMENT No. 1 TO THE
AERODROME DESIGN MANUAL PART 3
PAVEMENTS
Second E d i t i o n
-
19831. The purpose o f t h i s amendment i s t o u p d a t e t h e c o m p u t e r programmes, f o r t h e d e t e r m i n a t i o n of ACNs and t o i n c o r p o r a t e d a t a i n r e s p e c t of s e v e r a l new a i r c r a f t t y p e s . 2 . P l e a s e r e p l a c e t h e e x i s t i n g p a g e s by t h e a t t a c h e d c o r r e s p o n d i n g new pages.
3. Remove p a g e s 3 - 2 9 1 t o 3-298 which have been d e l e t e d by t h i s amendment.
I C A O
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2LJTDOC
9157-AN/901
AERODROME
DESIGN
MANUAL
PART
3
PAVEMENTS
SECOND EDITION
-
1983
Approved by the Secretav General and published under his authority
I C A O
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4 B 4 L 4 L b
0 0 3 9 3 6 7L B b
Published
inseparate English, French,
Russian and Spanish editions by the
lnternational
Civil Aviation Organization.
Allcorrespondence, except orders and subscriptions, should
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Japan. Japan Civil Aviation Promotion Foundation, 15- 12, 1 -chome, Toranomon,
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I C A O
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e
Aerodrome
Design
Manual
(DOC 9157-AN/901)
Part
3
Pavements
Second Edition
-
1983
d in the monthly
supplements to the Catabgue
of IC40
I44blimtkms, whichholden of
thispublication
should
consult.These
amendments are available free upon request.A M E N D M E N T S
The
issueof
amendments isannounced
inthe
ICAO Bulktin a n 1I C A O
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770
FOREWORD
T h i s r e v i s e d a n d u p d a t e d v e r s i o n of t h e Aerodrome Design
ManuaZ,
P a r t 3,i n c l u d e s g u i d a n c e on t h e d e s i g n of p a v e m e n t s i n c l u d i n g t h e i r c h a r a c t e r i s t i c s a n d on
e v a l u a t i o n a n d r e p o r t i n g of t h e i r b e a r i n g s t r e n g t h . The material i n c l u d e d h e r e i n i s c l o s e l y a s s o c i a t e d w i t h t h e s p e c i f i c a t i o n s c o n t a i n e d in Annex
14
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Aerodromes. The main p u r p o s e o f t h i s Manual i s t o e n c o u r a g e t h e u n i f o r m a p p l i c a t i o n o f t h o s e s p e c i f i c a t i o n s and t o p r o v i d e i n f o r m t i o n a n d g u i d a n c e t o S t a t e s . The s i g n i f i c a n t a d d i t i o n s / r e v i s i o n s t o the Manual as a r e s u l t of t h i s r e v i s i o n are:a) background information on t h e ACN-PCN method f o r r e p o r t i n g pavement
b e a r i n g s t r e n g t h ( C h a p t e r 1);
. *
b) material o n r e g u l a t i n g o v e r l o a d o p e r a t i o n s ( C h a p t e r 2);
c) u p d a t e d material on evaluatfon of pavements (Chapter 3 ) and on runway
s u r f a c e t e x t u r e a n d d r a i n a g e c h a r a c t e r i s t i c s ( C h a p t e r 5 ) ; d ) u p d a t e d material o n t h e d e s i g n - a n d e v a l u a t i o n o f p a v e m e n t s p r o v i d e d by Canada, F r a n c e , t h e U n i t e d Kingdom a n d s t h e U n i t e d S t a t e s ( C h a p t e r
4);
e) g u i d a n c e o n p r o t e c t i o n o f a s p h a l t p a v e m e n t s ( C h a p t e r 6 ) ; and f ) material o n s t r u c t u r a l d e s i g n c o n s i d e r a t i o n s f o r c u l v e r t s a n d b r i d g e s (Chapter 7).Chapter
4
o f t h i s Manual i s based on u p d a t e d material on pavement d e s i g n a n d e v a l u a t i o n s u b m i t t e d by S t a t e s a n d i s , t h e r e f o r e , b e l i e v e d t o b e c u r r e n t . S h o u l d a S t a t e , a t any time, c o n s i d e r t h a t t h e material i n c l u d e d t h e r e i n i s o u t o f d a t e , i t s h o u l d i n f o r m t h e S e c r e t a r y General o f t h i s and, i f p o s s i b l e , p r o v i d e a p p r o p r i a t e r e v i s e d material.I C A O
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T A B L E O F CONTENTS
Page
Glossary
...
(ix)Chapter 1.- Procedures for Reporting Aerodrome Pavement Strength
...
3-11.1 Procedure for pavements meant for heavy aircraft (ACN/PCN method)
...
3-11.2 Procedure for pavements meant for light aircraft
...
3-16Chapter 2.- Guidance on Overload Operations
...
3-172.1 Criteria suggested in Annex 14. Attachment B
...
3-172.2 State practices
...
3-172.2.1 Canadian practice
...
3-172.2.2 French practice
...
3-182.2.3 United Kingdom practice
...
3-20Chapter 3 . - Evaluation of Pavements
...
3-223.1 General
...
3-223.2 Elements of pavement evaluation
...
3-223.3 Elements of the ACN/PCN method
...
3-233.4 Assessing the magnitude and composition of traffic
...
3-253.5 Techniques for "using aircraft" evaluation
...
3-273.6 Techniques and equipment for "technical" evaluation
...
3-31Chapter
4.-
State Practices for Design and Evaluation of Pavements...
3-624.1
Canadian practice...
3-624.1.1
Scope...
3-624.1.2 Pavement design practices
...
3-644.1.3 Pavement evaluation practices
...
3-694.2 French practice
...
3-784.2.1 General
...
3-784.2.2 Choice of the design load
...
3-804.2.3 Designing flexible pavements
...
3-834.2.4 Designing rigid pavements
...
3-86I C A O
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4.2.6 Optimized design
...
3-109
4.2.7 Frost
...
3-112
4.2.8 Allowable loads
...
3-114
4.2.9 Evaluation
ofpavements
...
3-120
4.2.10 Reinforcement
of pavements
...
3-12;4.2.11 Light pavements
...
3-127
4.3 United Kingdom practice
...
3-129
4.3.1 Design
and
evaluation of pavements
...
3-129
4.3.2 Reporting pavement strength
...
3-129
4.4 United States of America practice
...
3-130
4.4.1
4.4.2
4.4.3
4.4.4
4.4.5
4.4.6
4.4.7
4.4.8
4.4.9
4.4.10
4.4.11
4.4.12
4.4.13
4.4.14
4.4.15
4.4.16
4.4.17
4.4.19
4.4.20
4.4.21
4.4.22
4.4.23
4.4.24
4.4.25
4.4.26
4.4.27
4.4.18
Introduction
...
Basic investigations and considerations
...
Soil tests
...
Unified soil classification system
...
Soil classification examples
...
Frost
and permafrost
...
Soil strength tests
...
Pavement design philosophy
...
Background
...
Aircraft considerations
...
Determination
ofdesign aircraft
...
Determination
ofequivalent annual departures
bythe
design aircraft
...
Designing the flexible pavement
...
Critical and non-critical areas
...
Stabilized base and sub-base
...
Stabilized sub-base and base equivalency factors
...
Design example
...
Designing the rigid pavement
...
Sub-base requirements
...
Critical and non-critical areas
...
Stabilized sub-base
...
Design example
...
Optional rigid pavement design curves
...
High traffic volumes
...
Reinforced concrete pavement
...
Airport pavement overlays
...
Pavement: evaluation
...
3-130
3-130
3-131
3-133
3-137
3-140
3-141
3-143
3-145
3-146
3-147
3-147
3-149
3-160
3-160
3-160
3-161
3-163
3-164
3-174
3-174
3-175
3-175
3-183
3-18
3
3-185
3-199
Chapter 5.- Methods for Improving Runway Surface Texture
...
3-204
5.1 Purpose
...
3-2045.2
Basic Considerations
...
3-204
5.3 Surface treatment
ofrunways
...
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Chapter 6.- Protection of Asphalt Pavements
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3-2256.1 The problem
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3-2256.2 Treatment of the problem
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3-2266.3 Protective coatings
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3-2266.4 Materials for protective coatings
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3-2276.5 Application
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3-2286.6 Protection gained
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3-2286.7 Maintenance consideration
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3-2296.8 Some related concerns
...
3-229Chapter 7.- Structural Concerns for Culverts and Bridges
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3-2307.1 Problem description
...
3-2307.2 Types of substructures
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3-2307.3. Some guiding concepts
...
3-2317.4 Evaluation of subsurface structures
...
3-2317.5 Considerations in design of new facilities
...
3-234C h a p t e r 8.- Construction of Asphaltic Overlays
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3-2378.1 Introduction
...
3-2378.2 Airport authority's role
...
3-2378.3 Design considerations
...
3-238BAppendix 1
.
Aircraft Characteristics Affecting Pavement Bearing Strength...
3-239Appendix 2
.
Procedures for Determining the Aircraft Classification Number ofan Aircraft
...
3-251Appendix 3
.
Pavement Design and Evaluation Graphs Provided by France...
3-299Appendix 4
.
Background Information on the United States Practice forthe Design and-Evaluation of Pavements
...
3-311Appendix 5
.
ACNs for Several Aircraft Types...
3-33931/8/89
No
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3 L bG L O S S A R Y
Terms which are d e f i n e d i n t h e ICAO Lexicon Volume I1 (Doc 9110) are used i n a c c o r d a n c e w i t h t h e m e a n i n g s a n d u s a g e s g i v e n t h e r e i n . A w i d e v a r i e t y o f terms i s i n u s e t h r o u g h o u t t h e w o r l d t o d e s c r i b e s o i l s , c o n s t r u c t i o n materials, and components of a i r p o r t p a v e m e n t s . A s f a r as p o s s i b l e t h e terms used i n t h i s document are t h o s e which h a v e t h e w i d e s t i n t e r n a t i o n a l u s e . However, f o r t h e c o n v e n i e n c e of t h e r e a d e r a s h o r t
l i s t of p r e f e r r e d terms and secondary terms which are c o n s i d e r e d t o b e t h e i r e q u i v a l e n t , and t h e i r d e f i n i t i o n s , i s given below.
P r e f e r r e d Term Secondary Term
Aggregate A i r c r a f t C l a s s i f i c a - t i o n Number (ACN) A s p h a l t i c c o n c r e t e Bitumen c o n c r e t e B a s e c o u r s e Base B e a r i n g s t r e n g t h CBR Compos it e pavement B e a r i n g c a p a c i t y Pavement s t r e n g t h C a l i f o r n i a B e a r i n g R a t i o D e f i n i t i o n General term f o r t h e m i n e r a l f r a g m e n t s o r p a r t i c l e s which, through the agency of a s u i t a b l e b i n d e r , c a n b e combined i n t o a s o l i d mass, e . g . , t o form a pavement. A number e x p r e s s i n g t h e r e l a t i v e e f f e c t of a n a i r c r a f t on a pavement f o r a - s p e c i f i e d s t a n d a r d s u b g r a d e s t r e n g t h . A g r a d e d m i x t u r e o f a g g r e g a t e , a n d f i l l e r w i t h a s p h a l t o r bitumen, placed h o t o r c o l d , a n d r o l l e d . The l a y e r o r l a y e r s of s p e c i f i e d o r s e l e c t e d material of designed thickness p l a c e d o n a s u b - b a s e o r s u b g r a d e t o s u p p o r t a s u r f a c e c o u r s e . The m e a s u r e o f t h e a b i l i t y o f a pave- ment t o s u s t a i n t h e a p p l i e d l o a d . The b e a r i n g r a t i o of s o i l determined by c o n p a r i n g t h e p e n e t r a t i o n l o a d o f t h e s o i l t o t h a t of a s t a n d a r d material
(see ASTM D1883). The method c o v e r s
e v a l u a t i o n o f t h e r e l a t i v e q u a l i t y of s u b g r a d e s o i l s b u t i s a p p l i c a b l e t o sub-base and some b a s e c o u r s e
materials.
A pavement c o n s i s t i n g of b o t h f l e x i b l e a n d r i g i d l a y e r s w i t h o r w i t h o u t
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P r e f e r r e d Term F l e x i b l e pavement Overlay Pavement C l a s s i f ica- t i o n Number (PCN) Pavement s t r u c t u r e P o r t l a n d
cement
c o n c r e t e Rigid pavement Sub-baae course Subgrade Surface
c o u r s e Secondary Term Pavement Concrete Su b+e e Formation foundation Wearing course D e f i n i t i o n A pavement s t r u c t u r e t h a t m a i n t a i n sintimate
c o n t a c t w i t h a n d d i s t r i b u t e s l o a d s t o t h e s u b g r a d e and depends on a g g r e g a t e i n t e r l o c k , p a r t i c l e f r i c t i o n , a n d c o h e s i o n f o r s t a b i l i t y . An a d d i t i o n a l s u r f a c e c o u r s e p l a c e d on e x i s t i n g pavement e i t h e r w i t h o r w i t h - o u t i n t e r m e d i a t ebase
o r s u b - b a e e c o u r s e s l u s u a l l y t o s t r e n g t h e n the pavement o r r e s t o r e t h e p r o f i l e o f t h e s u r f a c e . A number e x p r e s s i n g t h e b e a r i n g s t r e n g t h o f a pavement f o r u n r e s t r i c t e d operatione.The combination of sub-baae, baee
c o u r s e , a n d s u r f a c e c~llrse placed on a
s u b g r a d e t o s u p p o r t t h e t r a f f i c l o a d
a n d d i s t r i b u t e i t t o t h e subgrade.
A d x t u r e of g r a d e d a g g r e g a t e w i t h
P o r t l a n d cement and water.
A pavement s t r u c t u r e t h a t d i e t r i b u t e e l o a d s t o t h e s u b g r a d e h a v i n g as i t s
surface
c o u r s e a P o r t l a n d cement c o n c r e t e s l a b o f r e l a t l v e l y h i g h b e n d i n g r e s i s t a n c e . The l a y e r o r l a y e r s o f s p e c i f i e ds e l e c t e d material of designed thickness
p l a c e d
on
a s u b g r a d e t o s u p p o r t a b a s e courae. The u p p e r p a r t of t h e s o i l , n a t u r a l o r c o n e t r u c t e d , w h i c h s u p p o r t s t h e l o a d s t r a n s m f t t e d by t h e pavement. The t o p c o u r s e of a pavement s t r u c t u r e . JI C A O
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CHAPTER 1.- PROCEDURES FOR REPORTING AERODROME PAVEMENT STRENGTH
1 . 1 P r o c e d u r e f o r pavements meant f o r heavy a i r c r a f t (ACN-PCN method)
1 . 1 . 1 I n t r o d u c t i o n
1 . 1 . 1 . 1 Annex 14, 2.5.2 s p e c i f i e s t h a t t h e b e a r i n g s t r e n g t h of a pavement i n t e n d e d f o r a i r c r a f t of mass g r e a t e r t h a n 5 700 kg s h a l l b e made a v a i l a b l e u s i n g t h e a i r c r a f t c l a s s i f i c a t i o n number
-
pavement c l a s s i f i c a t i o n number (ACN-PCN) method. To f a c i l i t a t ea p r o p e r u n d e r s t a n d i n g a n d u s a g e o f t h e ACN-PCN method t h e f o l l o w i n g material explains:
a) t h e c o n c e p t o f t h e method; and
b) how t h e ACNs of a n a i r c r a f t are determined.
1 . 1 . 2 Concept of t h e ACN-PCN method
1 . 1
.
2 . 1 Annex 1 4 d e f i n e s ACN and PCN as f o l l o w s :-
Am. A number e x p r e s s i n g t h e r e l a t i v e e f f e c t of a n a i r c r a f t on a pavement f o r a s p e c i f i e d s t a n d a r d s u b g r a d e s t r e n g t h .
-
PCN. A number e x p r e s s i n g t h e b e a r i n g s t r e n g t h o f a pavement f o r u n r e s t r i c t e d o p e r a t i o n s .A t t h e o u t s e t , i t needs t o b e n o t e d t h a t t h e ACN-PCN method i s meant o n l y f o r p u b l i c a - t i o n of pavement s t r e n g t h d a t a in t h e A e r o n a u t i c a l I n f o r m a t i o n P u b l i c a t i o n s (AIPs). It i s n o t i n t e n d e d f o r d e s i g n o r e v a l u a t i o n of pavements, nor does i t c o n t e m p l a t e t h e u s e of a s p e c i f i c method by t h e a i r p o r t a u t h o r i t y e i t h e r f o r t h e d e s i g n o r e v a l u a t i o n of pavements. In f a c t , t h e ACN-PCN method d o e s p e r m i t S t a t e s t o u s e a n y d e s i g n / e v a l u a t i o n method of t h e i r c h o i c e . To t h i s end, t h e method s h i f t s t h e e m p h a s i s f r o m e v a l u a t i o n of pavements t o e v a l u a t i o n of l o a d r a t i n g of a i r c r a f t (ACN) a n d i n c l u d e s a s t a n d a r d proced- u r e f o r e v a l u a t i o n of t h e l o a d r a t i n g o f a i r c r a f t . The s t r e n g t h o f a pavement i s
r e p o r t e d u n d e r t h e method i n terms o f t h e l o a d r a t i n g o f t h e a i r c r a f t which t h e pavement c a n a c c e p t o n a n u n r e s t r i c t e d b a s i s . The a i r p o r t a u t h o r i t y c a n u s e a n y method of h i s c h o i c e t o d e t e r m i n e t h e l o a d r a t i n g o f h i s pavement.
If,
in t h e a b s e n c e of t e c h n i c a l e v a l u a t i o n , h e c h o o s e s t o go on t h e b a s i s o f t h e u s i n g a i r c r a f t e x p e r i e n c e , t h e n h ewould compute t h e ACN o f t h e most c r i t i c a l a i r c r a f t u s i n g o n e o f t h e p r o c e d u r e s
d e s c r i b e d below, c o n v e r t t h i s f i g u r e i n t o a n e q u i v a l e n t PCN a n d p u b l i s h i t in t h e A I P as t h e l o a d r a t i n g o f h i s pavement. The PCN so r e p o r t e d would i n d i c a t e t h a t a n a i r c r a f t w i t h a n ACN e q u a l t o o r less t h a n t h a t f i g u r e c a n o p e r a t e on t h e pavement s u b j e c t t o any
l i m i t a t i o n on t h e t i r e pressure.
1 . 1 . 2 . 2 The ACN-PCN method c o n t e m p l a t e s th e re p o r t i n g o f pavement s t r e n g t h s on a
continuous scale. The lower end of the scale i s z e r o a n d t h e r e i s no upper end. Addi-
t i o n a l l y , t h e same scale i s used t o measure t h e l o a d r a t i n g s of b o t h a i r c r a f t a n d pavements.
3-2 Aerodrome Design Manual
1 . 1 . 2 . 3 To f a c i l i t a t e t h e u s e of t h e method, a i r c r a f t m a n u f a c t u r e r s will p u b l i s h , i n t h e m
documents d e t a i l i n g t h e c h a r a c t e r i s t f c s of t h e i r a i r c r a f t , ACTS conputed a t ~ W O different
masses: maximum apron mass, and a r e p r e s e n t a t i v e o p e r a t i n g mass empty, both on r i g i d
and f l e x i b l e pavements and f o r t h e f o u r s t a n d a r d s u b g r a d e s t r e n g t h c a t e g o r i e s . N e v e r t h e l e s s ,
f o r t h e s a k e of convenience Annex 14, Attachment B and Appendix 5 hereto include a t a b l e
showing t h e ACNs of a number of a i r c r a f t . It is t o b e n o t e d t h a t t h e mass used i n t h e
ACN c a l c u l a t i o n is a "static" mass and that no allowance is made for an i n c r e a s e i n loading
through dynamic e f f e c t s .
1.1.2.4
The
ACN-PCN method a l s o e n v i s a g e s th e re p o r t i n g of the following informationi n
respect: of each pavement:a) pavement type;
b) subgrade category;
c ) -ximum t i r e p r e s s u r e a l l o w a b l e ; a n d d ) pavement e v a l u a t i o n method used.
The above d a t a
are
p r i m a r i l y i n t e n d e dt o
e n a b l e a i r c r a f t o p e r a t o r s t o d e t e r n d a e t h ep e r m i s s i b l e a i r c r a f t t y p e s a n d o p e r a t i n g masses, a n d t h e aircraft nranufacturers t o
e n s u r e c o m p a t i b i l i t y between a i r p o r t pavements and a i r c r a f t u n d e r development. There
i s , hawever,
no
need t o r e p o r t t h e actual subgrade s t r e n g t h o r t h e maxipaurnt i r e
p r e s s u r eallowable. Consequently, the s u b g r a d e s t r e n g t h s and t i r e preseures normally encountered
have
been grouped i n t o c a t e g o r i e s a8 i n d i c a t e d i n 1.1.3.2 belcw.It
would b e s u f f i c i e n t i f t h e a i r p o r t a u t h o r i t y i d e n t i f i e s t h e c a t e g o r i e s a p p r o p r i a t e t o h i s pavement. (Seea l s o t h e examples included under
Annex
14, 2.5.6. )1.1.3
How
ACNEare
determined1.1.3.1 The flow chart, below, b r i e f l y e x p l a i n s how t h e ACNs of a i r c r a f t are
ACN COMPUTER
*
,
PROGRAMMEI
I I RIGID DERIVED RIGID WHEEL CHART RIGIDPAVEMENT NOMOGRAPH$ SINGLE m I, RIGID PAVEMENT
’
+Y
A TABLE SHOWING ACNs OF AIRCRAFTI
I
I d ACN COMPUTER*
PROGRAMME1
I 1 , ICORPS OF ENGINEERS’ DERIVED FLEXIBLE
k ~ i
CHART FLEXIBLE PAVEMENT PAVEMENT
-
*
FLEXIBLE’ v NOMOGRAPHS *SINGLE WHEELI t
i-
I
Y
A TABLE SHOWING 3I C A O
9157 PARTs3
*Kt
m
484141rb
0039379
9 T B
m
3-4 Aerodrome Design Manual
1.1.3.2 Standard values used in t h e method and d e s c r i p t i o n o f th e v a r i o u s terms
a) S u b g r a d e c a t e g o r y . I n t h e ACN-PCN method e i g h t s t a n d a r d s u b g r a d e
v a l u e s (i .e., f o u r r i g i d p a v e m n t k v a l u e s a n d f o u r f l e x i b l e pavement
CBR v a l u e s ) a r e u s e d , r a t h e r t h a n a continuous scale of subgrade
s t r e n g t h s . The grouping
of
s u b g r a d e s w i t h a s t a n d a r d v a l u e a t t h em i d r a n g e of each group i s c o n s i d e r e d t o b e e n t i r e l y a d e q u a t e f o r
reporting. The s u b g r a d e s t r e n g t h categories are i d e n t i f i e d as high,
medium, low a n d u l t r a low a n d a s s i g n e d t h e following numerical
values:
S u b g r a d e s t r e n g t h c a t e g o r y
High s t r e n g t h ; C h a r a c t e r i z e d by k* = 150 MN/m3 a n d r e p r e s e n t i n g all k
values above 120
~ / I E ?
f o r r i g i d pavements, and by CBB 15 andr e p r e s e n t i n g
a l l
CBR values above 13 f o r f l e x i b l e pavements.Medium s t r e n g t h ; c h a r a c t e r i z e d by
k
= 80 HH/m3 a n d r e p r e s e n t i n g arange i n
k
of60
t o 120MN/
d
f o r r i g i d pavements, and by CBB 10 andr e p r e s e n t i n g a range i n CBR of 8 t o 13 € o r f l e x i b l e pavements.
Low s t r e n g t h ; c h a r a c t e r i z e d by
k
=40
MWm3 a n d r e p r e s e n t i n g a r a n g ei n k o f 25 t o 60
HN/d
f o r r i g i d pavements, and by CBB 6 andr e p r e s e n t i n g a range
i n
CBB of4
t o 8 f o r f l e x i b l e pavements.Ultra l o w s t r e n g t h ; c h a r a c t e r i z e d by k 20 MN/rn3 a n d r e p r e s e n t i n g a l l
k
v a l u e s below 25M
N
d
/
f o r r i g i d pavemente, and by CBR = 3 andr e p r e s e n t i n g a l l CBB v a l u e s b e l o w 4 € o r f l e x i b l e pavements.
b ) C o n c r e t e w o r k i n g e t r e s 8 f o r r i g i d pavements. For r i g i d pavements, a
s t a n d a r d s t r e s s f o r r e p o r t i n g p u r p o s e s is s t i p u l a t e d (a = 2.75 MPa)
o n l y
as
a means of e n e u r i n g u n i f o r m r e p o r t i n g . The working stress t ob e u s e d f o r t h e d e s i g n a n d / o r e v a l u a t i o n of pavements h a s no
r e l a t i o n s h i p t o t h e s t a n d a r d stress f o r r e p o r t i n g .
c )
Tire
p r e s s u r e . The r e e v l t a of pavement r e s e a r c h a n d r e - e v a l u a t i o n o f o l d t e s t r e s u l t s r e a f f i r m t h a t e x c e p t f o r u n u s u a l pavement construc-t i o n
(i.e.,
f l e x i b l e pavements witha
t h i n a e p h a l t i c c o n c r e t e c o v e r o rweak u p p e r l a y e r s ) ,
t i r e
p r e e s u r e effectsare
secondary t oload
andwheel spacing, and may t h e r e f o r e b e c a t e g o r i z e d i n f o u r g r o u p s f o r
r e p o r t i n g p u r p o s e s as: high, medium, low and very low and assigned
t h e f o l l o w i n g n u m e r i c a l v a l u e s :
High
-
No
p r e s s u r e lidtMedium
-
P r e s s u r e l i m i t e d t o 1.50 MPaLow
-
P r e s s u r e l i m i t e d t o 1.00 MPaVery
low
-
P r e s s u r e l i m L t e d t o 0.50 MPa*
Values determined using a 75cm
d i a m e t e r p l a t e .P a r t 3 . - Pavements 3-5
d ) M a t h e m a t i c a l l y d e r i v e d s i n g l e w h e e l l o a d : The concept of a
m a t h e m a t i c a l l y d e r i v e d s i n g l e w h e e l l o a d h a s b e e n employed i n t h e
ACN-PCN method as a means t o d e f i n e t h e l a n d i n g g e a r / p a v e m e n t i n t e r a c t i o n w i t h o u t s p e c i f y i n g pavement t h i c k n e s s as a n ACN parameter. T h i s i s done by e q u a t i n g t h e t h i c k n e s s g i v e n by t h e m a t h e m a t i c a l model f o r a n a i r c r a f t l a n d i n g g e a r t o t h e t h i c k n e s s f o r a s i n g l e w h e e l a t a s t a n d a r d t i r e p r e s s u r e o f 1.25 MPa. The s i n g l e w h e e l l o a d s o o b t a i n e d i s t h e n u s e d w i t h o u t f u r t h e r r e f e r e n c e t o t h i c k n e s s ; t h i s i s so
b e c a u s e t h e e s s e n t i a l s i g n i f i c a n c e i s a t t a c h e d t o t h e f a c t of h a v i n g e q u a l t h i c k n e s s e s , i m p l y i n g "same a p p l i e d stress t o t h e pavement", r a t h e r t h a n t h e m a g n i t u d e of t h e t h i c k n e s s . The f o r e g o i n g i s i n a c c o r d w i t h t h e o b j e c t i v e o f t h e ACN-PCN method t o e v a l u a t e t h e r e l a t i v e l o a d i n g e f f e c t o f a n a i r c r a f t on a pavement.
e) A i r c r a f t c l a s s i f i c a t i o n number (ACN). "he ACN of a n a i r c r a f t i s n u m e r i c a l l y d e f i n e d as two times t h e d e r i v e d s i n g l e w h e e l l o a d , w h e r e t h e d e r i v e d s i n g l e w h e e l l o a d i s e x p r e s s e d i n thousands of kilograms.
A s n o t e d p r e v i o u s l y , t h e s i n g l e w h e e l t i r e p r e s s u r e i s s t a n d a r d i z e d a t 1.25 MPa. A d d i t i o n a l l y , t h e d e r i v e d s i n g l e w h e e l l o a d i s a f u n c t i o n o f t h e s u b g r a d e s t r e n g t h . The a i r c r a f t c l a s s i f i c a t i o n number (ACN) is
d e f i n e d o n l y f o r t h e f o u r s u b g r a d e c a t e g o r i e s (i.e., h i g h , medium, low, a n d u l t r a low s t r e n g t h ) . The "two" ( 2 ) f a c t o r i n t h e n u m e r i c a l d e f i n i t i o n o f t h e ACN i s used' t o achieve. a s u i t a b l e ACN v s . g r o s s mass
scale so t h a t w h o l e number ACNs may b e u s e d w i t h r e a s o n a b l e a c c u r a c y .
1.1.3.3
Because a n a i r c r a f t o p e r a t e s a t v a r i o u s mass a n d c e n t r e of g r a v i t y c o n d i t i o n s t h e f o l l o w i n g c o n v e n t i o n s h a v e b e e n u s e d in ACN computa- t i o n s (see F i g u r e 1-1).
1) t h e maximum ACN of a n a i r c r a f t i s c a l c u l a t e d a t t h e mass and c.g.
t h a t p r o d u c e s t h e h i g h e s t main g e a r l o a d i n g o n t h e pavement, u s u a l l y t h e maximum ramp mass a n d c o r r e s p o n d i n g a f t c . g . The
a i r c r a f t tires are c o n s i d e r e d as i n f l a t e d t o t h e m a n u f a c t u r e r s
recommendation f o r t h e c o n d i t i o n ;
2) relative a i r c r a f t ACN c h a r t s a n d t a b l e s show t h e ACN as a f u n c t i o n of a i r c r a f t g r o s s mass w i t h t h e a i r c r a f t c.g. a t a c o n s t a n t v a l u e c o r r e s p o n d i n g t o t h e maximum ACN v a l u e ( i . e . , u s u a l l y , t h e a f t c . g . f o r max ramp mass) and a t t h e max ramp mass t i r e p r e s s u r e ; and
3) s p e c i f i c c o n d i t i o n ACN v a l u e s are t h o s e ACN v a l u e s t h a t are
a d j u s t e d f o r t h e e f f e c t s o f t i r e p r e s s u r e a n d / o r c . g . l o c a t i o n , a t a s p e c i f i e d g r o s s mass f o r t h e a i r c r a f t .
A b b r e v i a t i o n s
a) A i r c r a f t p a r a m e t e r s
3-6 Aerodrome Design Manual
b)
Pavementand
sstbgredr parePetereQ
-
Standard working
e t r e m
f o r reporting, 2.75 HPat
-
Pavementthickneus
i n centimetresmickueso of
s l a b for ri@d pavemente, orTotal
thickness
of pav-at structuralsyeter
burface t osubgrade)
f o r flcxible p a v e ~ e n t e
(see Figure 1-21.Figure 1-1. Landing gear loading on pavement
Part 3.- Pavements
a
3-7THEORETICAL ASPHALT PAVEMENT THEORETICAL CEMENT CONCRETE PAVEMENT
e
7 ’
THICKNESS
1 ‘
Figure 1-2
k
-
Westergaard’s modulus of subgrade reaction in MN/m3R
-
Westergaard’s radius of relative stiffness in centimetres.This is computed using the following equation (see Figure 1-3).
E is modulus of elasticity p is Poisson’s ratio
(+
= 0.15) 12 ( 1-
p2)kPHYSICAL MEANING OF W E S T E R G A A R D S
‘RADIUS O F
R E L A T I V E
STIFFNESS’,L
S I N G L E W H E E L L O A D I N G O N A S L A B , p A P P R O X l M A T E L Y \ IN SLAB 1 I1
CONTRAFLEXURE+
tL---
I DEFLECTION. .
-
-. .--
PLOT OF BENDING MOMENT BOTTOM OF SLAB AS A (AND/OR TENSION STRESS O N FUNCTION OF RADIAL DISTANCE FROM CENTER
L W OF LOAD)
3-8 Aerodrome Design Manual
CBR
-
California Bearing Ratio i n p e r c e n tTire P r e s s u r e s
P,
-
Tire p r e s s u r e f o r d e r i v e d s i n g l e w h e e l l o a d-
1.25 MPa Pq-
Tire p r e s s u r e f o r a i r c r a f t a t maximre ramp mass c o n d i t i o n1.1.3.4 Mathematical models. Two mathematical models are used i n t h e ACN-PCN
method: t h e W e s t e r g a a r d s o l u t i o n f o r a loaded e l a s t i c p l a t e on a Uinkler foundation
( i n t e r i o r l o a d case) f o r r i g i d pavements, and t h e B o u s s i n e s q s o l u t i o n f o r s t r e s s e s a n d
d i s p l a c e m e n t s i n a homogeneous i s o t r o p i c e l a s t i c h a l f - s p a c e u n d e r s u r f a c e l o a d i n g f o r
f l e x i b l e pavements. The u s e o f t h e s e two, widely used, models permits the maximum
c o r r e l a t i o n t o w o r l d w i d e pavement design methodologies, with a minimra need f o r pave-
ment p a r a u e t e r v a l u e s (i.e., only approximate subgrade k, o r CBR v a l u e s are r e q u i r e d ) .
1.1.3.5 Computer programmes. The two computer programmes d e v e l o p e d u s i n g t h e s e
mathematical models are reproduced i n Appendix 2. The p r o g r a m f o r e v a l u a t t n g a i r c r a f t
on r i g i d pavements i s based
on
t h e p r o g r a m d e v e l o p e d by Mr. R.G. Packard* of P o r t l a n dCement A s s o c i a t i o n , I l l i n o i s ,
USA
a n d t h a t f o r e v a l u a t i n g a i r c r a f t on f l e x i b l e pavementsi s based on t h e US Army Engineer Waterways Experiment S t a t i o 3 I n s t r u c t i o n R e p o r t S-77-1,
e n t i t l e d " P r o c e d u r e s f o r Development of CBR Design Curves". It may, however, be noted
t h a t t h e a i r c r a f t c l a s s i f i c a t i o n t a b l e s i n c l u d e d i n Annex 14, Attachment B and i n
Appendix 5 of t h i s Manual c o m p l e t e l y e l i m i n a t e t h e n e e d t o u s e t h e s e programmes i n
r e s p e c t of most o f t h e a i r c r a f t c u r r e n t l y in use.
1.1.3.6 Graphical procedures. Aircraft for which pavement thickness requirement
c h a r t s h a v e been published by t h e m a n u f a c t u r e r s c a n a l s o be e v a l u a t e d u s i n g t h e g r a p h i -
c a l p r o c e d u r e s d e s c r i b e d below.
1.1.3.7 Rigid pavements. This procedure uses the conversion chart shown i n
F i g u r e 1-4 and t h e pavement t h i c k n e s s r e q u i r e m e n t c h a r t s p u b l i s h e d by t h e a i r c r a f t
manufacturers. The Portland Cement Association computer programme r e f e r r e d t o i n
1.1.3.5 was used i n developing Figure 1-4. This f i g u r e relates t h e d e r i v e d s i n g l e w h e e l
l o a d a t a c o n s t a n t t i r e p r e s s u r e of 1.25 MPa t o a r e f e r e n c e pavement t h i c k n e s s . It
t a k e s i n t o a c c o u n t t h e f o u r s t a n d a r d s u b g r a d e k v a l u e s d e t a i l e d in 1.1.3.2 a ) above, and
a s t a n d a r d c o n c r e t e stress of 2.75 HPa. The f i g u r e a l s o i n c l u d e s a n ACN scale which
p e r m i t s t h e ACN t o be r e a d d i r e c t l y . The f o l l o w i n g steps are u s e d t o d e t e r m i n e t h e ACN
o f a n a i r c r a f t :
a) using t h e pavement r e q u i r e m e n t c h a r t p u b l i s h e d by the manufacturer
o b t a i n t h e r e f e r e n c e t h i c k n e s s f o r t h e g i v e n a i r c r a f t mass,
k
v a l u e oft h e s u b g r a d e , a n d t h e s t a n d a r d c o n c r e t e stress f o r r e p o r t i n g , i.e.
2.75 MPa;
b ) u s i n g t h e a b o v e r e f e r e n c e t h i c k n e s s a n d F i g u r e 1-4, o b t a i n a d e r i v e d
s i n g l e w h e e l l o a d f o r t h e s e l e c t e d s u b g r a d e ; and
*
Refer t o document e n t i t l e d "Design of Concrete Airport Pavement" by R.G. Packard,D SW L (1 000 kg)
120
t40
t
20'
t0 I
70
6c)
5c
4c
3c
20
10
0
HIGH STRENGTH 150 MN/m” /.I// / / MEDIUM STRENGTH LOW STRENGTH ’ 80 MN/m3 //J - 40 MN/m? ULTRA-LOW STRENGTH- -- 20 MN/m3TIRE PRESSURE 1.25 MPa STANDARD STRESS 2.75 MPa
PCA COMPUTER PROGRAMME PDILB
S
io
1
20
25
30
35
40
45
50
55
REFERENCE THICKNESS
3-10 Aerodrome Design Manual
c) t h e a i r c r a f t c l a s s i f i c a t i o n number, a t t h e s e l e c t e d mass and subgrade k v a l u e , i s two tirnes t h e d e r i v e d s i n g l e w h e e l l o a d i n
1 000 kg. Note t h a t t h e ACN c a n a l s o b e read d i r e c t l y from t h e c h a r t . Note f u r t h e r t h a t t i r e p r e s s u r e c o r r e c t i o n s a r e n o t n e e d e d
when t h e above procedure is used.
1.1.3.8 F l e x i b l e pavements. This p r o c e d u r e u s e s t h e c o n v e r s i o n c h a r t shown i n F i g u r e 1-5 and t h e pavement t h i c k n e s s r e q u i r e m e n t c h a r t s p u b l i s h e d by t h e a i r c r a f t
manufacturers based on t h e ~ i t e d States Army Ehgineers CBR procedure. The former
c h a r t h a s b e e n d e v e l o p e d u s i n g t h e f o l l o w i n g e x p r e s s i o n :
Where t = r e f e r e n c e t h i c k n e s s
i n
cm.DSWL = a s i n g l e w h e e l l o a d w i t h 1.25 HPa t i r e p r e s s u r e
ps = 1.25 MPa
CBR = standard subgrade (Note t h a t t h e c h a r t u s e s f o u r s t a n d a r d v a l u e s 3, 6 , 10 and 15)
C 1 0.5695 C2 = 32.035
The r e a s o n f o r u s i n g t h e l a t t e r charts i s t o o b t a i n t h e e q u i v a l e n c y b e t w e e n t h e " g r o u p
of l a n d i n g g e a r w h e e l s e f f e c t " t o a d e r i v e d s i n g l e w h e e l l o a d by means of Boussinesq Deflection Factors. The f o l l o w i n g s t e p 8 are u s e d t o d e t e r m i n e t h e ACN of a n aircraft:
a ) u s i n g t h e pavement requirement chart p u b l i s h e d by the manufacturer d e t e r d n e t h e r e f e r e n c e t h i c k n e s s f o r t h e g i v e n a i r c r a f t mass,
subgrade category, and 10 000 coverages;
b) e n t e r F i g u r e 1-5 w i t h t h e r e f e r e n c e t h i c k n e s s d e t e r m i n e d i n s t e p a ) and t h e CBR corresponding t o the subgrade category and read the
d e r i v e d s i n g l e wheel load; and
c ) t h e ACN a t t h e s e l e c t e d m e 8 and subgrade category i e two times t h e
d e r i v e d s i n g l e w h e e l l o a d i n 1 000 kg. Note t h a t t h e ACN c a n a l s o b e r e a d d i r e c t l y f r o m t h e chart. Note f u r t h e r t h a t t i r e p r e s s u r e c o r r e c t i o n s are not needed when t h e above procedure Le used.
1.1.3-9 Tire p r e s s u r e a d j u s t m e n t t o ACN. M r c r a f t n o r m a l l y h a v e t h e i r t i r e s i n f l a t e d t o t h e p r e s s u r e c o r r e s p o n d i n g t o t h e m a x i u u m g r o s s mass a n d m a i n t a i n t h i s p r e s s u r e r e g a r d l e s s of t h e v a r i a t i o n s i n t a k e - o f f masses. There are times, however, when o p e r a t i o n s a t reduced masses and reduced t i r e p r e s s u r e s are productive and reduced
ACNE need t o b e c a l c u l a t e d . To d o t h i s f o r r i g i d pavements, a c h a r t h a s b e e n p r e p a r e d by t h e u s e of t h e PCA computer programme PDLLB and is g i v e n
i n
F i g u r e 1-6. The example i n c l u d e d in t h e c h a r t i t s e l f e x p l a i n s how t h e c h a r t is used.I C A O
9357
P A R T * 3**
m
4 8 4 3 4 3 6
0019386 038
m
P a r t 3 .-
Pavements 3-11ACN
100
90
€ul
70
60
50
40
30
20
10
REFERENCE THICKNESS
CM
3-12 Aerodrome Design Manual
1
.
1.3.10 For f l e x i b l e pavements, t h e CBR e q u a t i o n t =\
L F Z
w a s u s e d t o e q u a t e t h i c k n e s s a n d s o l v e f o r t h e r e d u c e d p r e s s u r e ACN i n terms of t h e
maximm t i r e p r e s s u r e ACN a t the reduced mass g i v i n g t h e f o l l o w i n g e x p r e s s i o n :
1.1.3.11
ACN = ACN
Reduced Maximm
p r e s s u r e p r e s s u r e
(For values
of
C1 and C2 see 1.1.3.8.)Worked
examples
Solution: The ACN of t h e a i r c r a f t f r o m t h e t a b l e i n Appendix 5 of t h i s Manual i s
48.
It i s a l s o p o s s i b l e t o d e t e r m i n e t h e ACN of t h e a i r c r a f t u s i n g F i g u r e 1-4
a n d t h e pavement r e q u i r e m e n t c h a r t for t h e a i r c r a f t i n F i g u r e 1-7. This
method i n v o l v e s t h e f o l l o w i n g o p e r a t i o n s :
a) from Figure 1-7 r e a d t h e t h i c k n e s s of c o n c r e t e n e e d e d f o r t h e a i r c r a f t
mass of 78 500 kg, t h e s u b g r a d e k v a l u e of 80 MN/m3, a n d t h e s t a n d a r d c o n c r e t e stress of 2.75 MPa as 31.75 cm; and
b)
e n t e r F i g u r e 1-4 w i t h t h i s t h i c k n e s s a n d r e a d t h e ACN of t h e a i r c r a f tI C A O
9357
P A R T * 3**
m
h 8 4 L 4 3 b0039388 900
m
P a r t 3.- Pavements 3-13 1.2 1.1 1 .o CORRECTION FACTOR ACN ACNSTD .9.a
.7 .E7
’ An aircraft with a tire pressure of 1.25 MPa has would be its ACN if tire pressure is increased an ACN of 50 on a medium subgrade. What
to 1.50 MPa?
To obtain the correction factor proceed verti- medium subgrade curve is intercepted. Then proceed horizontally and read 1.06.
ACN for TP 1.50 MPa =
1.06 x 50 = 53
Pavement thickness = 40 cm
-
cally from a tire pressure of 1-50 MPa until.5 .75 1 .o 1.25 1.5 1.75 2.0 2.35 2.50
TIRE PRESSURE MPa
F i g u r e 1-6. ACN t i r e p r e s s u r e a d j u s t m e n t
-
r i g i d p a v e m e n t s o n l y+. - _
I C A O
9L57 PART*K3
**
E 48YLYLb
0059389 847
H
3-14 Aerodrome Design Manual
Example 2: An A I P c o n t a i n s t h e f o l l o w i n g i n f o r m a t i o n related t o a runway pavement:
PCN o f t h e pavement = 80
Pavement t y p e r i g i d
Subgrade category medium s t r e n g t h
Tire p r e s s u r e l i m i t a t i o n = none
Determine whether the pavement c a n a c c e p t t h e f o l l o w i n g a i r c r a f t a t t h e
i n d i c a t e d o p e r a t i n g m a s s e s a n d t i r e p r e s s u r e s :
MaSS Tire p r e s s u r e
-
Airbus A 300 Model B2 a t 142 000 kg 1.23 MPa
B747-100 a t 334 751 kg 1.55 MPa
Concorde a t 185 066 kg 1.26 MPa
DC- 10-40 a t 253 105 kg 1.17 HPa
Solution: ACNs o f t h e s e a i r c r a f t f r o m Appendix 5 of t h i s Manual are 44, 51, 71 and
53, r e s p e c t i v e l y . S i n c e the pavement i n q u e s t f o n h a s a PCN of 80 i t c a n
a c c e p t a l l o f t h e s e aircraft.
Example 3: F i n d t h e ACN of DC-10-10 a t 157 400 kg on a f l e x i b l e pavement r e s t i n g on a
medium s t r e n g t h s u b g r a d e (CBR 10). The t i r e p r e s s u r e o f t h e m a i n w h e e l s
is 1.28 MPa.
Solution: The ACN of t h e a i r c r a f t f r o m Appendix 5 of t h i s Manual is
(196 406
-
157 400) (196 406-
108 940) 57-
x (57-27) 39006
87 466 I 5 7--
x 30 = 57-
13.4 = 43.6 o r5
It i s a l s o p o s s l b l e t o d e t e r m t n e t h e ACN o f t h e a i r c r a f t u s i n g F i g u r e 1-5a n d t h e pavement r e q u i r e n e n t c h a r t i n F i g u r e 1-8. This method i n v o l v e s
t h e f o l l o w i n g o p e r a t i o n s :
a) from Figure 1-8 r e a d the t h i c k n e s s o f p a v e m e n t n e e d e d f o r t h e a i r c r a f t
mass of 157 400 kg a n d t h e s u b g r a d e CBR of 10 as
57
cm; andb) e n t e r F i g u r e 1-5 with this t h i c k n e s s and r e a d t h e ACN of a i r c r a f t €or
m
e
I C A O
7357
P A R T * 3 f *H
4 B 4 1 4 L b
0037390
5 6 9
Part 3 . - Pavements
124.5 x 43.2 c m TIRES
-
TIRE PRESSURE CONSTANT AT 11.7 kglcm’127 x 53.3 c m TIRES (NEW DESIGN)
-
TIRE PRESSURE CONSTANT AT 11.7 kg/cm*THE MAXIMUM LOAD REFERENCE LINE AND “DESIGN OF CONCRETE AIRPORT
ANY VALUE OF k ARE EXACT. FOR LOADS PAVEMENT” AND “COMPUTER PROGRAMME NOTE: THE VALUES OBTAINED BY USING REFERENCES:
LESS THAN MAXIMUM. THE CURVES ARE u<- FOR AIRPORT PAVEMENT DESIGN
-
ACT FOR k = 80 BUT DEVIATE SLIGHTLY FORPROGAMME
PDILB.”OTHER VALUES OF k. PORTLAND CEMENT ASSN.
RIGID PAVEMENT REQUIREMENTS-
PORTLAND CEMENT ASSOCIATION DESIGN METHOD
MODELS 727-100, -1OOC AT 77 200 kg; 727-200 STANDARD AT 78 500 kg, ADVANCED 727-200 AT 89 800 kg AND 95 300 kg MAXIMUM RAMP MASS.
F i g u r e 1-7
I C A O
9357 P A R T * 3
**
444lr4bb
0019391
4T5
3-16 Aerodrome Design Manual
FLEXIBLE PAVEMENT THICKNESS cm
0 ,
25
50
75
100
125
150
175
108 862
kg OPERATING MASS EMPTY 157396
kgMAXIMUM
LANDING MASS
195 579 kg MAXIMUM TAKE-OFF MASS
I / / I I I I I I I I I I I I I t
3
5
7
9
20
40
6 0 8 0
2
4
6
8
1Q
30
50
70
SUBGRADE CBR (PERCENTAGE)
F i g u r e 1-8. DClO-10 F l e x i b l e Pavement Requirements 1 0 000 Coverages aft c.g.
1.2 Procedure
for
pavements meant f o r l i g h t aircraft:1.2.1 The ACN-PCN method d e s c r i b e d i n 1.1 is n o t i n t e n d e d f o r r e p o r t i n g
s t r e n g t h o f pavements meant f o r l i g h t
a i r c r a f t ,
i . e . , t h o s e w i t h mass less than 5 700 kg.Annex 1 4 s p e c i f i e s a s i m p l e p r o c e d u r e f o r e u c h pavements. This procedure envisages the
r e p o r t i n g o f only two elements: maxirmm a l l o w a b l e a i r c r a f t mass and maximot allowable
t i r e pressure. It is important t o
note
t h a t t h e t i r e p r e s s u r e c a t e g o r i e s of the ACN-PCNmethod
(1.1.3.2,
c ) )are
n o t u s e d f o r r e p o r t i n gmaxiaum
a l l o w a b l e t i r e pressure.I n s t e a d , a c t u a l
t i r e
p r e s s u r elimits
are r e p o r t e das
i n d i c a t e d in t h e f o l l o w i n gexample:
CHAPTER
2.-
GUIDANCE ON OVERLOADO P E R A T I O N S
2.1 Criteria suggested i n Annex 14, Attachment B
2.1.1 O v e r l o a d i n g o f p a v e m e n t s c a n r e s u l t e i t h e r f r o m l o a d s t o o l a r g e o r f r o m a s u b s t a n t i a l l y i n c r e a s e d a p p l i c a t i o n r a t e o r both. Loads l a r g e r t h a n t h e d e f i n e d ( d e s i g n o r e v a l u a t i o n ) l o a d s h o r t e n t h e d e s i g n l i f e w h i l s t smaller l o a d s e x t e n d i t . With t h e exception of massive overloading, pavements i n t h e i r s t r u c t u r a l b e h a v i o u r a r e n o t s u b j e c t t o a p a r t i c u l a r l i m i t i n g l o a d a b o v e w h i c h t h e y s u d d e n l y o r c a t a s t r o p h i c a l l y f a i l . Behaviour i s s u c h t h a t a pavement c a n s u s t a i n a d e f i n a b l e l o a d f o r a n e x p e c t e d number o f r e p e t i t i o n s d u r i n g i t s d e s i g n l i f e . As a r e s u l t , o c c a s i o n a l m i n o r o v e r l o a d i n g i s a c c e p t a b l e , when e x p e d i e n t , w i t h only l i m i t e d l o s s i n pavement l i f e expectancy and
r e l a t i v e l y small a c c e l e r a t i o n o f pavement d e t e r i o r a t i o n . F o r t h o s e o p e r a t i o n s i n w h i c h magnitude of o v e r l o a d a n d / o r t h e f r e q u e n c y of u s e d o n o t j u s t i f y a d e t a i l e d a n a l y s i s t h e f o l l o w i n g c r i t e r i a a r e suggested: a) f o r f l e x i b l e p a v e m e n t s o c c a s i o n a l movements by a i r c r a f t w i t h ACN n o t e x c e e d i n g 10 p e r c e n t a b o v e t h e r e p o r t e d PCN s h o u l d n o t a d v e r s e l y a f f e c t t h e pavement; b ) f o r r i g i d o r c o m p o s i t e p a v e m e p t s , i n w h i c h a r i g i d pavement l a y e r p r o v i d e s a p r i m a r y e l e m e n t o f t h e s t r u c t u r e , o c c a s i o n a l movements by a i r c r a f t w i t h ACN n o t e x c e e d i n g 5 p e r c e n t a b o v e t h e r e p o r t e d PCN s h o u l d n o t a d v e r s e l y a f f e c t t h e pavement; c) i f t h e pavement s t r u c t u r e is unknown t h e 5 p e r c e n t l i m i t a t i o n s h o u l d apply; and
d ) t h e annual. number o f o v e r l o a d movements s h o u l d n o t e x c e e d
a p p r o x i m a t e l y 5 p e r c e n t o f t h e t o t a l a n n u a l a i r c r a f t movements. 2.1.2 Such o v e r l o a d movements s h o u l d n o t n o r m a l l y b e p e r m i t t e d o n pavements e x h i b i t i n g s i g n s o f d i s t r e s s o r f a i l u r e . F u r t h e r m o r e , o v e r l o a d i n g s h o u l d b e a v o i d e d
d u r i n g a n y p e r i o d s o f t h a w f o l l o w i n g f r o s t p e n e t r a t i o n o r when t h e s t r e n g t h of t h e pavement o r i t s subgrade could be weakened by water. Where o v e r l o a d o p e r a t i o n s a r e c o n d u c t e d , t h e a p p r o p r i a t e a u t h o r i t y s h o u l d r e v i e w t h e r e l e v a n t pavement c o n d i t i o n r e g u l a r l y a n d s h o u l d a l s o r e v i e w t h e c r i t e r i a f o r o v e r l o a d o p e r a t i o n s p e r i o d i c a l l y s i n c e e x c e s s i v e r e p e t i t i o n o f o v e r l o a d s can c a u s e s e v e r e s h o r t e n i n g o f pavement l i f e o r r e q u i r e m a j o r r e h a b i l i t a t i o n o f pavement. 2.2 S t a t e practices 2.2.1 C a n a d i a n p r a c t i c e 2.2.1.1 The t e c h n i c a l a s s e s s m e n t of a p r o p o s e d o v e r l o a d o p e r a t i o n i s b a s e d o n th e " o v e r l o a d r a t i o " c o n c e p t . The o v e r l o a d r a t i o i s a measure of t h e l o a d imposed by t h e a i r c r a f t r e l a t i v e t o t h e n o m i n a l d e s i g n s t r e n g t h o f t h e pavement. For f l e x i b l e pavements, t h e o v e r l o a d r a t i o i u p o s e d by a n a i r c r a f t i s determined by c a l c u l a t i n g t h e s u b g r a d e b e a r i n g s t r e n g t h r e q u i r e d f o r t h e e x i s t l n g t h i c k n e s s o f pavement, u s i n g t h e d e s i g n e q u a t i o n g i v e n i n 4.1,2.2. This c a l c u l a t e d s u b g r a d e b e a r i n g s t r e n g t h i s t h e n d i v i d e d by t h e a c t u a l s u b g r a d e b e a r i n g s t r e n g t h t o f o r m t h e o v e r l o a d r a t i o . For r i g i d 3-17
SCAO 9157 PART*3 ** W 4BL1/4Lb 00119393 278 -
3-18 Aerodrome Design Manual
pavements, the overload ratio is defined as the flexural stress imposed in the slab by
the aircraft divided by the design flexural stress of 2.75 HPa.
2.2.1.2 Cn the basis of these overload ratios, aircraft operations are classified
as follows:
Overload Ratio Operational Classification
less than 1.25 unrestricted
1.25 to 1.50 limited
1.50 to 2.00 marginal
greater than 2.00 emergency use only
2.2.1.3 The approval of operations classified as limited or marginal involves the
risk of an accelerated rate of pavement deterioration and shortened service life. This
risk increases with increasing value of overload ratio and frequency of operations.
The decision to approve such operations therefore depends on the willingness of the
airport authority to fund pavement rehabilitation measures earlier than may otherwise be
necessary. Normal practice at airports operated by Transport Canada is to permit
aircraft operations falling into the limited and marginal classifications, unless
otherwise dictated by age and condition of the pavement, or funding constraints.
2.2.1.4 Similar considerations apply to permitting operations by aircraft with
tire pressures higher than restrictions reported. Provided the overload ratio is less
than 1.50, aircraft are normally permitted to operate with tire pressures one range
higher than the tire pressure range for which the pavement was designed. These ranges
are indicated in 4.1.2.6.
2.2.2 French practice
l
2.2.2.1 The information publiehed on the basis of one or the other method
described in 4.2.8 does not permit a complete reflection of the operating condition
of the pavement. The following procedure should therefore be used to assess the euita-
bility of the pavement for the intended aircraft. Reference is made to the flexible
pavement or rigid pavement requirement graph for the subject aircraft in Appendix 3.
These graphs and the pavement data enable the exact authorized load for the particular
undercarriage to be determined. In the event that the aircraft is not shown in Appendix
3, characteristics that are closest to the subject aircraft will be selected. If the
resulting load is higher than the expected aircraft load , the allowable stresses of the
pavement will not be exceeded, and the aircraft can use the pavement without adverse
effects. Should the load established by means of the graph be less than the expected
aircraft load, there will be an effective overload and acceptance of the aircraft will
require special permission.
2.2.2.2 Concessions. It should be noted that the risk to the aircraft itself when
landing on a runway without adequate bearing strength is minimal, unless the load it
imposes is considerably more than the bearing strength of the runway. Generally
speaking, the acceptance of an exceseively heavy aircraft will undoubtedly cause damage
to the pavement, without detriment to the aircraft itself. The user will in no case be
held responsible for deteriorations of this type. however, in no case should an
aircraft load exceed by more than 50 per cent the allowable load for the subject
aircraft, in other words an actual overload co-efficient P/PO higher than 1.5 for all
