FLEXIBLE PAVEMENT DESIGN

Civil Engineering Department | DCC3113 : Highway & Traffic Engineering



DCC3113 :







e-
Course Notes






| Unit 1 : Introduction to Highway and Traffic

| Unit 2 : Pavement Materials

| Unit 3 : Construction Of Flexible Pavement

| Unit 4 : Construction Of Rigid Pavement

| Unit 5: Flexible Pavement Design


| Unit 6 : Highway Maintenance

| Unit 7 : Transportation Planning

| Unit 8 : Traffic Control Equipment And Road Furniture

| Unit 9 : Junction Design

| Unit 10 : Traffic Management


Prepared By :
SITI ZURAIFA BINTI MD SAH |Lecturer in Civil Engineering Department, Politeknik Mukah, Sarawak
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| Introduction


| Video


| Concept


| Assessment


| Summary






Prepared By :
SITI ZURAIFA BINTI MD SAH |Lecturer in Civil Engineering Department, Politeknik Mukah, Sarawak
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Introduction





COURSE LEARNING OUTCOMES (CLO)

Upon completion of this course, students will be able to:-
CLO 1 : Apply the fundamentals concepts and principles of highway and traffic engineering and related act in Malaysia. (C3)



CONTENT


5.1
Know the
basic design
of flexible
pavement
UNIT 5:
FLEXIBLE
PAVEMENT
DESIGN

5.2
Understand
the design
of flexible
pavement






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Introduction





COURSE LEARNING OUTCOMES (CLO)

Upon completion of this course, students will be able to:-
CLO 1 : Apply the fundamentals concepts and principles of highway and traffic engineering and related act in Malaysia. (C3)



CONTENT


5.1
Know the
basic design
of flexible
pavement
UNIT 5:
FLEXIBLE
5.1.1 State the factors that are
considered in designing the PAVEMENT
thickness of flexible DESIGN
pavement.
5.2
a. Failure criteria Understand
b. Traffic loading the design
c. Traffic decaying power of flexible
d. Environmental effect pavement





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Civil Engineering Department | DCC3113 : Highway & Traffic Engineering




Introduction





COURSE LEARNING OUTCOMES (CLO)

Upon completion of this course, students will be able to:-
CLO 1 : Apply the fundamentals concepts and principles of highway and traffic engineering and related act in Malaysia. (C3)



CONTENT

5.2.1 Describe the design factors of
5.1 thickness of pavement
Know the a. Traffic load
basic design b. Design life
of flexible c. Sub-grade condition
pavement d. Drainage
UNIT 5: 5.2.2 Explain traffic loads and axle
FLEXIBLE weight
PAVEMENT 5.2.3 Adopt the Public Work
DESIGN Department flexible design
pavement method.
5.2
Understand
the design
of flexible
pavement






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Video















































Source: How to Design a Road (https://www.youtube.com/watch?v=oKgWk-U4eMI)


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Concept












































Figure 5.1: Flexible Pavement Structural Layers





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Know the basic design of flexible pavement






• Pavement Thickness Design is the determination of required thickness of various
pavement layers to protect a given soil condition for a given wheel load


• Aim: to design a structure that will ensure that the transmitted stresses are sufficiently

reduced and do not exceed the capacity of the underlying subgrade.


































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The factors that are considered in designing the thickness of flexible

pavement




• Failure criteria

• Traffic loading Failure criteria


• Traffic decaying power

• Environmental effect




Environmental
effect Traffic loading











Traffic
decaying
power








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Failure criteria






• Two failure mechanisms are permanent deformation and cracking of the bituminous
layers.


• The definition from Croney, failure as transformation shape or deflection of 20mm tire’s

lane not speeding that measuring from ground level.




Slow zone Fast zone


Vertical
Deformation
or
Rutting











Figure 7-1 : A Typical Profile of a Road Cross Section Showing Rutting Along the Wheel Path




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Traffic Loadings






• Protection of the sub-grade from the loading imposed by traffic is one of the primary
functions of a pavement structure. The designer must provide a pavement that can


withstand a large number of repeated applications of a variable-magnitude loading.


• Traffic loading comprise of :

i. Tire load and pressure

ii. Axle and wheel configurations


iii. Load repetition


iv. Traffic distribution

v. Vehicle Speed


vi. Equivalent Standard Axle (ESA)











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Traffic Decaying Power






• Every time an axle load acts on a pavement, damage is inflicted onto the pavement.

• Real traffic composition is a mixture of varying weights & numbers of axles.


• According to this concept, one application of standard axle load inflicts one unit of

damage to the pavement.

































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Environmental Effect






• Environment in which a flexible pavement is to be established has an important influence
on the behavior and performance of the various materials in the pavement and sub-


grade.


• Probably the two climatic factors of major significance are:

i. Temperature

ii. Moisture



Seepage
from
highlands Water ponding




Seepage through Seepage through
shoulder pavement

Water content rises in subgrade

Subgrade looses strength and stability


Figure 7-2: Environmental Effect


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Describe the design factors of thickness of pavement





• Traffic load
• Design life

• Sub-grade condition
• Drainage



































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Traffic Loadings






• The primary loading factors that are important in flexible pavement design are

i. Magnitude of axle load

ii. Wheel Configuration


iii. Volume and Composition of axle load


iv. Tyre pressure and Contact Area


Single Axle Tandem Axle Tridem Axle






















Figure 7-3: Traffic Loading

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Traffic Loadings






• The standard axle load, Ls, is equivalent to 80 kN or 8200 kg or 18,000 pounds.

• One application of a load L, is equivalent in terms of damage to F applications of the

standard load Ls where


e = F = (L/Ls) 4

 Consider only commercial vehicles CV (BTM > 1.5 ton, 3 ton for RN31)




























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Calculation to define load equivalency factor for different type of

vehicles






Lorry 9 tonnes
Car 1.5 tonnes


= 0.00114
= 1.48














= 3.67
= 103.1
Bus 18 tonnes Trailer 26 tonnes



Figure 7-4: Calculation to define load equivalency factor for
different type of vehicles




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Example






















120 kN 100 kN 80 kN



The total load of a commercial vehicle is 300kN and is transmitted to the pavement
via three axles. The first axle is 120kN, second 100kN and the third is 80kN. The value
of equivalent factor, F.

F = (L/Ls)
4
F = (120/80) + (100/80) + (80/80)
4
4
4
F = 8.50






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Traffic Loading Concept























5 T 17 T 16 T


ESAL = ( 5 /8.16 ) + (17 / 8.16) + (16 / 8.16) 4
4
4

= 0.141 + 18.84 + 14.78

= 33.76 standard axle



Design Traffic = 25 million standard axle
= (25 x 10 ) / 33.76 = 740,521 nos of above truck.
6

The pavement will fail after 740,521 nos. of the above truck moving on top of

ACW20 surface



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Design life






• The design life refers to the span of time between the initial opening to traffic until the
pavement requires a strengthening overlay.


• The design life should not be confused with the pavement life since the pavement life

can be extended by routine maintenance and rehabilitation.


• The typical design life is 10 years.


• The design life on JKR Design Method is suggested for 10 years.

• The design life begins from the road starts in use for traffic until the maintenance is

required.



















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Sub-grade condition





• In case of varying CBR for 1m depth of sub-grade, mean CBR is determined as follows:


CBR = [(h CBR 1/3 + h CBR 1/3 + … + h CBR 1/3 ) / (1000)]
3
2
2
1
m
n
n
1

Where:
CBR = mean CBR for that location
m
CBR1, CBR2, … CBR = CBR of soil strata
n
h , h , … h = thickness of soil strata (mm)
n
2
1
h + h + … + h = 1000 mm
n
1
2

• A minimum CBR of 5% is recommended for pavements that have to support traffic
volumes corresponding to Traffic Classes T2 through T5.
• For road pavements that designed for large volumes traffic (Traffic Classes T4 and T5), a
minimum sub-grade strength corresponding to CBR of 12% is recommended. For
pavements design purposes, the use of average CBR or sub-grade modulus test results is
not recommended.







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Drainage






• To ensure the safety of the travelling public, careful consideration must be given to
remove the runoff from the roadway through the structure of the pavement drainage


facilities.




































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Adopt the Public Work Department flexible design pavement method




Malaysian Design Methods


• Adopt design method based on AASHTO Guide, and catalogue of structure method:

i. Arahan Teknik Jalan 5/85 – based on AASHTO road test, developed using multi-


layered elastic theory. Suitable for major roads with heavy and medium traffic

ii. Overseas Road Note 31 – based on research in tropical and sub-tropical countries













The latest!!!
R5 Arahan Teknik Jalan 2015












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Pavement thickness Design Arahan Teknik Jalan 5/85






• Data required:

i. Design life, x – suggests 10 years

ii. Class of roads


iii. Initial Annual Daily Traffic – AADT (Veh/day)


iv. Percentage of Commercial Vehicle – Pc

v. Average annual traffic growth – r


vi. Sub-grade strength – CBR

vii. Terrain condition


















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Design Procedure:





Calculate Initial Annual Comercial Vehicle Traffic per direction, Vo





Where
AADT = average annual daily traffic (veh/day) in both direction

Pc = percentage of commercial vehicles
D = Directional distribution (0.50 if directional split is 50:50)

L = Lane distribution (1.00 if single lane)



Total Number of Commercial Vehicles per direction, Vc





Where r = traffic growth rate

x = Design life


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Design Procedure:





Total Equivalent Standard Axles, ESA





ESA = Vc x e





Where, e = equivalent factor (Refer Table 3.1 in (Arahan Teknik (Jalan) 5/85 or e = 2.52)


























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Design Procedure:





Daily Traffic Flow at the end of the design period, Vx





V = V (1 + r) Where V = AADT / 2 (per direction)
x
1
1
x





























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Design Procedure:





Capacity Estimation




Maximum Hourly Capacity, c


c = I x R x T


Where I = Ideal hourly capacity (Refer Table 3.2 in (Arahan Teknik (Jalan) 5/85)


R = Roadway Reduction Factor (Refer Table 3.3 in (Arahan Teknik (Jalan) 5/85)

T = Traffic Reduction Factor (Refer Table 3.4 in (Arahan Teknik (Jalan) 5/85)


















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Design Procedure:





Daily Capacity, C


C = 10 x c


Note: Assume c is 10% of C


Check C > V
x



If C > Vx  Capacity will not be exceeded at the end of the design period (OK)

If C < Vx  Capacity will be exceeded by the end of the design period (not OK)




When C < Vx happens, need to reduce design period.





Years required to reach capacity,


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Design Procedure:





Thickness Calculation, TA


T = a D + a D + … + a D
1
A
1
n
n
2
2
Where a , a , a = Structural Coefficients (Refer Table 3.5 in (Arahan Teknik (Jalan) 5/85)
1
2
3
D , D , D = Layer Thickness (Based on Refer Table 3.6, 3.7 and 3.8 in (Arahan Teknik
1
2
3
(Jalan) 5/85)
























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Design Procedure:



















































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Design Procedure:



















































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Design Procedure:



















































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Design Procedure:




Define equivalent thickness, TA’ using Nomograph Thickness


Based on subgrade CBR, ESA and TA values (Using Figure 2)


In case of varying CBR for 1m depth of sub-grade, mean CBR is determined as follows:

CBR = [(h CBR 1/3 + h CBR 1/3 + … + h CBR 1/3 ) / (1000)]
3
1
m
n
2
n
1
2

Where:
CBR = mean CBR for that location
m
CBR1, CBR2, … CBR = CBR of soil strata
n
h , h , … h = thickness of soil strata (mm)
n
1
2
h + h + … + h = 1000 mm
n
1
2

Make sure TA ≥ TA’


Sketch the designed thickness



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4 cm



6 cm






20 cm

(crushed
agg)


15 cm














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Wearing Course (40 mm)





BinderCourse (60 mm)`







Roadbase (200 mm)







Sub-base (150 mm)





Subgrade (300 mm)







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Try this apps






































Click here











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Example using apps



















































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Example using apps



















































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Example





The following conditions are given:
• Class of road JKR 05

• Initial daily traffic volume (ADT) 6,600
• Percentage of commercial vehicles 15%

• Annual growth rate 7%

• Equivalence factor 2.0
• Subgrade CBR 5%
• Rolling terrain

























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Example





• Initial annual commercial traffic for one way, Vo


V o = 6600 x 0.15 x 0.5 x 365 = 181,000


• Accumulative sum of commercial traffic one way for 10 year design period


10
V = 181,000 [(1 + 0.07) - 1]
c
---------------------------------
0.07
= 2.50 x 10
6


• Total Equivalent Standard Axles


ESA = 2.0 x 2.5 x 10
5
= 5.0 x 10
6







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Example





• Maximum Hourly One Way Traffic Flow


c = I x R x T
c = 1000 x 1.0 x 0.77 = 770 vehicles per hour



• Assuming hourly capacity is ten per cent of daily capacity.

C = 7700 veh/day/lane



• The estimated daily traffic V after 10 years is given by

Vx = 6,600 (1 + 0.07) 10

---------------------

2
= 6490 veh/day/lane


• Hence capacity has not been reached after 10 years.



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Example





• Design of Layer Thickness

TA = a D + a D + ... + a D
n
1
2
2
1
n
1st Trial
Nominate D1 = 12.5 cm
D2 = 18.0 cm
D3 = 20.0 cm

Then TA = 1.0 x 12.5 + 0.32 x 18 + 0.23 x 20
= 25.36 cm < TA'


2nd Trial D1 = 15.0 cm
D2 = 20.0 cm
D3 = 20.0 cm


Then TA = 1.0 x 15 + 0.32 x 20 + 0.23 x 20

= 26.0 cm

Make sure TA ≥ TA’, so choose 2 trial
nd


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Example





Taking into consideration the minimum thickness requirements, the pavement structure then
comprise of the following layer thicknesses


Wearing - 5 cm
Binder - 10 cm

Base - 20 cm Wearing Course (5 cm)

Subbase - 20 cm Binder Course (10 cm)

20 cm




20 cm







20 cm











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Exercise




























Note:
Requirement of pavement layers:
Wearing Course = Asphalt Concrete.
Road-Base Course = Crushed Aggregate
Sub-Base Course = Sand


Assume road shoulder width 2.0m and carriageway width 7.5m.







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Exercise





A road with hierarchy of 05 has a surface width of 7.0 m and shoulder width of 2.00m is to be
built as a main road in a residential area. It has a initial average daily traffic of 6800cv/day in
both directions. The rate of traffic growth is 7%. Percentage of commercial vehicle is 25%.
Design a flexible pavement for the road which needs a design life of 10 years. The CBR for
sub-grade of the road is 5%. ( Employ the JKR Malaysia Design Method ).


Note:

Requirement of pavement layers:
Wearing Course = Asphalt Concrete.

Road-Base Course = Broken Aggregate.
Sub-Base Course = Broken Aggregate.

Flat Terrain















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Exercise




A pavement is to be designed to last 10 years. The Average Daily Traffic volume is 7,700.
Other condition of the pavement is listed below. Determine the structural number or
pavement thickness.


Class of road JKR 04 (road type is 2 lanes both ways)
Carriageway & Shoulder width 7 m ; 2 m

Terrain type Flat
PC % 12%
Growth rate 4%
Sub-grade CBR 5%

Base material Mechanically stabilized crushed aggregate
Sub-base material Crushed aggregate


















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Exercise





Chess of road JKR 05
Initial daily traffic volume (ADT) 3300 per lane

% of commercial vehicle 15%
Annual growth rate 7%

Carriageway & Shoulder width 7 m ; 2 m
Sub-grade CBR 8%

Rolling terrain
Base material Cement stabilized

Sub-base material Crushed aggregate




















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