Pavement Design - Civil Engineering

7/27/2019 Pavement Design - Civil Engineering

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MANAGEMENT OF INFRASTRUCTUREAND COMMUNITY DEVELOPMENT

Pavement Design


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MANAGEMENT OF INFRASTRUCTURE AND COMMUNITY DEVELOPMENT

What will you learn?

You will learn about types of pavement structure,

asphalt pavement design method, rigid pavementdesign method


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What competency do you want to expect?

Knowledge competency: You will recognize types

of pavement structure, asphalt pavement designmethod, rigid pavement design method.

Skill competency: you are able to bridge

communication between community and

engineering service provider (roadplanner/designer/contractor) in regards with

suitable pavement structure to support

development of community and region according

to cost availability and site condition


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Contents

Types of pavement structures

Asphalt pavement design method

Rigid pavement design method


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Cross section of roman road


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Types of pavement: roman road pavement


7/78MANAGEMENT OF INFRASTRUCTURE AND COMMUNITY DEVELOPMENT

Types of pavement: early modern road pavement

(Tresaguet, Telford, McAdam)



Types of pavement: early modern road pavement

(Tresaguet, Telford, McAdam)



Types of pavement: modern road pavement



Details of rigid pavement joints



Types of rigid pavement

(b) Jointed reinforced concretepavement (JRCP) (max. length

of 30 m per slab)

(max. length of 6 m per slab)



Road construction on swamp and wetland area



Haul road



Asphalt pavement design method

Load distribution in asphalt pavement

Properties of flexible pavements Design objectives and constraints

AASHTO, 1993 Design Method

Pavement damage



Load distribution in asphalt pavement

Asphalt pav. is designed to provide sufficient

thickness to distribute the applied load with

depth



Properties of flexible pavements

Fast Deterioration with Time

Repeated Loads Variable Load Configuration

Variable Load Magnitude

Variable Tyre Pressure

Traffic Growth

Change of Material Properties with Environmental Conditions

Change of Subgrade Properties with Distance

Channelized Traffic Load

Multi-Layer System

Unconventional Failure Definition



Design objectives

The objectives of pavement design can be listed as

follow Maximum economy, safety, and serviceability over

the design period

Maximum or adequate load-carrying capacity in

terms of load magnitude and repetitions Minimum or limited deteriorations over the design

period

Minimum or limited noise or air pollution during

construction Minimum or limited disruption of adjoining land use

Maximum or good aesthetics



The constraints

The pavement designer typically faces several economic,

physical, and technical design constraints such as, Availability of time and fund for design and construction

Minimum allowable level of serviceability before rehabilitation

Availability of materials

Minimum and maximum layer thickness

Capabilities of construction and maintenance personnel andequipment

Testing capabilities

Capabilities of structural and economic models available

Quality and extent of the design data available



AASHTO, 1993 Design Method

Equivalent Single Axle Load (ESAL)

Design Procedure



Equivalent Single Axle Load (ESAL)

Traffic loads applied on the pavement surface range from light passenger cars to heavytrucks. To design a pavement section the damage caused by all axle loads that will be

applied on the pavement during its designed life has to be considered. Different magnitudes and different numbers of repetitions are converted to an equivalent

number of repetitions of a standard axle load that causes the same damage to thepavement. A standard axle load was selected as 18000 Lb (80 kN) applied on a singleaxle with a dual wheel at each end.

The ESAL is the equivalent number of repetitions of the 18-kip (80 kN) standard axleload that causes the same damage to the pavement caused by one-pass of the axle

load in question. Equivalent Axle Load Factors (EALF) to relate the damage caused by different load

magnitudes and axle configurations to the standard axle load as shown in Equationbelow

where Wt18 is the number of 18-kip (80-kN) single-axle load applications to time t(failure) and Wtx is the number of x-axle load applications to time t (failure).



Equivalent Axle Load Factors, Single axles



Equivalent Axle Load Factors, tandem axles



Equivalent Axle Load Factors, triple axles


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Equations to calculate pavement thickness

Lx is the load in kips on one single axle, one set of tandem axles, or

one set of triple axles;

L2 is the axle code (1 for single, 2 for tandem axles, and 3 for tripleaxles);

pt is the terminal serviceability index

b18 is the value of bx when Lx is equal to 18 and L2 is equal to one.

SN is the structural numbers, which is an index that combines theeffect of material properties, layer thicknesses and drainage quality

ESAL at first day and cumulatif ESAL during design


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ESAL at first day and cumulatif ESAL during design

life

ESAL at first day may be calculated as follow

Cumulatif ESAL during design life can be calculated as follow

where

Ni is the number of repetitions of axle group i,

EALFi is the equivalency factor for axle group

m is number of axle groups

n is the designed life of the pavement in years i is the expected annual traffic growth rate.


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Since the EALFs are not very sensitive to SN, a SN value of 5 maybe assumed in most cases. Unless the design thickness issignificantly different, no iterations will be needed


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Design Procedure

Step 1 Reliability

Step 2

Overall Standard Deviation Step 3 Cumulative Equivalent Single Axle Load

Step 4 Effective Roadbed Soil Resilient Modulus

Step 5 Resilient Moduli of Pavement Layers

Step 6 Serviceability Loss

Step 7

Structural Numbers

Step 8 Structural Layer Coefficients

Step 9 Drainage Coefficients

Step 10 Layer Thicknesses

Step 11

Freeze or Thaw and Swelling (additional) Step 12 Life-Cycle Cost (additional)


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Step 1 Reliability

A reliability level (R) is selected depending on the

functional classification of the road and whether theroad is in urban or rural area. The reliability is thechance that pavement will last for the design period

without failure. A larger reliability value will ensure

better performance, but it will require larger layerthicknesses.


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Step 2 Overall Standard Deviation

The overall standard deviation So takes into

consideration the variability of all input data. The1993 design guide recommends an approximaterange of 0.4 to 0.5 for flexile pavements


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Step 3 Cumulative Equivalent Single Axle Load

In this step, the designer assumes a designed life, typically in the range of 10

to 20 years. The cumulative expected 18-kip (80-kN) ESAL (W18) during the

designed life in the design lane is then determined as discussed earlier. If thecumulative two-directional 18-kip ESAL is known, the designer must factor

the design traffic by directions by multiplying by the directional distribution

factor (D) to get the ESAL in the predominate direction. For example, if the

traffic split during the peak hour is 70 30%, D is taken as 0.7.

To get the ESAL in the design (right) lane, the design traffic in the

predominant direction is multiplied by the lane distribution factor (L)


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Step 4 Effective Roadbed Soil Resilient Modulus

Worksheet for

estimating effectiveroadbed soil resilient

modulus


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Step 5 Resilient Moduli of Pavement Layers

The resilient moduli MR of the surface, base,

and subbase layers are either determined usinglaboratory testing or estimated using previouslydeveloped correlations


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Step 6 Serviceability Loss

The serviceability loss is the difference between the

initial serviceability index (po) and the terminalserviceability index (pt). The typical Po value for anew pavement is 4.6 or 4.5. The recommended

values of pt are 3.0, 2.5 or 2.0 for major roads,

intermediate roads and secondary roads,respectively


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Step 7 Structural Numbers

The required structural number above the

subgrade (SN3) is determined using followingequation (that also can be described using thefigure).

Figure 8.22


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Step 8 Structural Layer Coefficients

The structural layer coefficient is a measure of the relativeability of a unit thickness of a given material to function as astructural component of the pavement.

Three structural layer coefficients (a1, a2 and a3) are requiredfor the surface, base and subbase, respectively.

Chart for estimating structural

layer

coefficient of dense-graded

asphalt concrete based on

the elastic (resilient) modulus

(a1)


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Chart for estimating structural

layercoefficient of base course (a2)


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Chart for estimating structural layer coefficient of sub

base (a3)


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Step 9 Drainage Coefficients

Drainage coefficients are measures of the quality of

drainage and the availability of moistures in thegranular base and subbase


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Step 10 Layer Thicknesses

Minimum Thickness (in.) (AASHTO, 1993)


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Sample Problem 1


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Solution


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Solution (continued)


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Solution (continued)


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Rigid pavement design method

Characteristics and Load Transmission of

Rigid Pavements Considerations for Structural Design of

Rigid Pavement

Computation of Design Traffic Loading

Material Properties for Design of Rigid

AASHTO Procedure for Thickness Design of

Concrete Pavement

Reinforcement Design of Rigid Pavement

Joints and Load Transfer Design

Characteristics and Load Transmission of Rigid


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Characteristics and Load Transmission of Rigid

Pavements

The rigid pavement relies on rigid slab action anddesigned to spread the load over a large area

Considerations for Structural Design of Rigid


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Considerations for Structural Design of Rigid

Pavement

(a) Determination of soil properties, design traffic

loadings and environmental parameters

(b) Selection of materials for various pavement layers

(c) Structural thickness design of pavement layers

(d) Drainage design for the pavement system(e) Safety and geometric design


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The computation of design traffic loading involves the followingsteps:

(a) Estimation of the initial year traffic volume and composition

(b) Estimation of the annual traffic growth rate by vehicle type

(c) Estimation of directional split of design traffic

(d) Estimation of design lane traffic

(e) Estimation of the magnitudes of wheel loads by vehicle type(f) Computation of the number of applications of wheel loads in

the design lane

Information concerning (a) and (b) can be obtained fromtraffic survey and forecast based on historical trends orprediction using transportation models.


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Directional Split and Design Lane Traffic Loading


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Traffic Loading Computation:

Structural analysis and design of pavement requires the knowledge

of (a) the magnitudes of axle loads in the design traffic, and (b) thenumber of times each of these loads will be applied on the design

lane during the design life of the pavement.

Two forms of field survey are required to obtain the required

information from similar highway type within the same region.

First, traffic count surveys must be conducted to determine thenumber of vehicle types in the design traffic. For pavement design, it

is necessary to classify vehicles by size and axle configuration, such

as cars, buses, single-unit trucks, and different types of multiple-unit

trucks.

Second, a survey to measure the axle or wheel loads of each vehicle

type. Such axle or wheel load survey can be performed at weighingstations or using weigh-in-motion devices. Data collected from the

two forms of survey enable one to compute the number of

repetitions by axle type


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Vehicle Classification for Pavement Design


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Example of Axle Load Data for Pavement Design


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ESAL factor in rigid pavement design

AASHTO Load Equivalency Factors for Rigid Pavements Based on


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q y g

Terminal Serviceability Index of 2.5 for Tandem Axles and pt of 2.5

AASHTO Load Equivalency Factors for Rigid Pavements Based on


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q y g

Terminal Serviceability Index of 2.5 for Tandem Axles and pt of 2.5

AASHTO Load Equivalency Factors for Rigid Pavements Based on Terminal


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Serviceability Index of 2.5Triple Axles (i.e., Tridem Axles) and pt of 2.5



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Serviceability Index of 2.5Triple Axles (i.e., Tridem Axles) and pt of 2.5

S l bl 2


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Sample problem 2

S l bl 3


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Sample problem 3


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F l f C i T l D i L di


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Formula for Computing Total Design Loading

S l bl 4


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Sample problem 4

M i l P i f D i f Ri id P


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Material Properties for Design of Rigid Pavement

roce ure or c ness es gnof Concrete Pavement: Procedure


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of Concrete Pavement: Procedure

Reliability

Pavement Material Properties Load Transfer Coefficient

Drainage Coefficient

Slab Thickness Requirement

Reliability


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Reliability


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Chart for estimating composite k


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Chart for estimating composite k

Chart for k as a function of bedrock depth


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Chart for k as a function of bedrock depth

Ch t f ti ti l ti d t i id t


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Chart for estimating relative damage to rigid pavements

Correction of effective modulus of subgrade reaction for

t ti l l f bb t


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potential loss of subbase support

Values for Loss of Support Factor LS


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Values for Loss of Support Factor LS

Sample problem 5 and 6


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Sample problem 5 and 6

Sample problem 5

Sample problem 6

Load Transfer Coefficient


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Load Transfer Coefficient



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Slab Thickness Requirement and sample problem 7


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Slab Thickness Requirement and sample problem 7

Sample problem 7

Rigid pavement thickness design chart


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Rigid pavement thickness design chart



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Reinforcement Design for JRCP


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Reinforcement Design for JRCP

Sample problem 8


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Sample problem 8

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