Lectures of of 22. . Week 1414. . 09 09 . . 20132013site.iugaza.edu.ps/wp-content/uploads/2_%20Week,%20Stage...Prof. Dr. Eng Shafik Jendia Advantages of Stage Construction 2- Difficulties

Prof. Dr. Eng Shafik JendiaProf. Dr. Eng Shafik Jendia

Stage ConstructionStage Construction

Lectures of Lectures of 22. Week. Week

1414. . 09 09 . . 20132013

Prof. DR.Prof. DR. Eng. Shafik JendiaEng. Shafik Jendia

Islamic University of GazaIslamic University of Gaza


Standard and RegulationStandard and Regulation

- AASHTO, Guide for Design of Pavement Guide for Design of Pavement Structures.Structures.

- ASPHALT INSTITUTE, , Thickness Design of Asphalt Pavements for Highways Thickness Design of Asphalt Pavements for Highways & Streets & Streets MANUAL SERIES NO. (MS-1) 1991.


Planned stage construction is the construction of roads and streets by applying successive

layers of asphalt concrete according to design and to a predetermined time schedule.

The design of planned stage construction should not be confused with the design of major maintenance or the rehabilitation of

existing pavements.

Stage ConstructionStage Construction


Advantages of Stage ConstructionAdvantages of Stage ConstructionThere are several circumstances in which

stage construction is advantageous:1- When there is not quite enough money to construct the full (say, 20-year) design

thickness, the pavement may be designed for construction in two stages, the first

stage being designed for a shorter time period. It is important, however, that plans

be made to have funds


Advantages of Stage ConstructionAdvantages of Stage Construction

2- Difficulties in estimating traffic for a period of 20 to 25 years. particularly for city streets

and some low-volume rural roads, make planned stage construction attractive. A facility can be designed for a shorter time period (i.e., lesser amount of traffic) and traffic counts can then be made when the facility is in use. From this in-service data, improved estimates of the

later traffic are possible.


Advantages of Stage ConstructionAdvantages of Stage Construction3- Experience indicated that pavements

overlaid after they had been subjected to traffic performed somewhat better than new

pavements of equal design.


Advantages of Stage ConstructionAdvantages of Stage Construction4- Weak spots that develop during the first stage can be repaired and revised traffic

data will be available.

5- savings may be realized from reduced final thickness or from extended life of the

original pavement.


The procedure, as applied is based on the

presumption that the second stage will be

constructed before the first stage shows serious signs of

distress.

Stage Construction / Stage Construction / Asphalt Institute


Stage Construction / Stage Construction / AASHTO


Reliability and Stage construction Reliability and Stage construction AlternativesAlternatives


Reliability and Stage Construction Reliability and Stage Construction AlternativesAlternatives


ForFor

Reliability and Stage Construction Reliability and Stage Construction AlternativesAlternatives

1 - Design RequirementsTime ConstraintsTime ConstraintsThe analysis period The analysis period selected for this design example is selected for this design example is 20 20

yearsyears. The maximum . The maximum performance period performance period (or (or service lifeservice life) ) selected for the selected for the initial flexible pavement structure initial flexible pavement structure in this in this example is example is 15 15 yearsyears..

Thus , it will be necesary to consider Thus , it will be necesary to consider stage construction stage construction (i. (i. e. Planned rehabilation) alternatives to develop design e. Planned rehabilation) alternatives to develop design strategies which will strategies which will last the ananlysis periodlast the ananlysis period..


Stage Construction / ExampleStage Construction / Example

TrafficBased on average daily traffic and axle weight data from the planning group, the estimated two-way 18-kip equivalent single axle (ESAL)applications during the first year of the pavement’s = 2.5 x 106 and theprojected growth rate is 3 % per year. The directional distribution factor(DD) is asumed to be 50 % and lane distribution factor (DL) for the facility (assume three lanes in one diredtion) is 80 %

During the first year (in the design lane) During the first year (in the design lane) = 2.5 x 106 x 0.5 x 0.8 = 1.0 x 106 18-kip ESAL applications





A plot of the cumulative 18-kip ESAL traffic over

20- year analysis period.

The curve and equation for future traffic (w18) are reflective of the

assumed exponential growth rate (g) of 3 %

Reliability (R)AlthoughAlthough the facility will be a heavily trafficed state highway, it is in a rural the facility will be a heavily trafficed state highway, it is in a rural

situation where daily traffic volumes should never exceed half of its situation where daily traffic volumes should never exceed half of its capacity.capacity.

ThusThus, a , a 9090--percent overall reliability percent overall reliability level was selected for design. This level was selected for design. This means that for a twomeans that for a two--stage strategy (initial pavement + one overlay), the stage strategy (initial pavement + one overlay), the design reliability for each stage must be design reliability for each stage must be 00..909011//2 2 or or 95 95 %.%.

SimilarySimilary, for a three , for a three ––stage strategy (initial pavement + two overlays) , the stage strategy (initial pavement + two overlays) , the reliability for all three stages must be reliability for all three stages must be 00..909011//33 or or 9696..5 5 %.%.

Standard Deviation (So)An approximate An approximate standard deviation value of standard deviation value of 00..3535 will be used for the will be used for the

purpose of this example problem.purpose of this example problem.



ServiceabilityThe overall design serviceability loss (∆PSI = po – pt)

for this problem is: ∆PSI = ∆PSI = 22..11

Resilient ModulusResilient ModulusApplication of the effective roadbed soil MR

estimation procedure results in a value of 5700 psi



Pavement Layer Material CharacterizationThree types of pavement materials will constitute the individual

layers of the structure. The moduli for each determined using the recommended laboratory test procedures, are as follows:





AASHTO GUIDE






SN = 5.6




Overlay Thickness (Second Stage) Home work



Two Stage Strategy (Initial Structure +

Overlay)

Overlay (second stage)

Initial Structure (first sage)

Design Analysis Period (20 years)

Performance Period (5 years)


Period (years)

26.9 x 106?18 x 106W18(ESAL)

??5.6 SN ??66.0 cm

(26 inch)Thickness

Find thicknesses of all pavement layers for a three stage strategy for the same data of the previous example


Stage Construction / Stage Construction / Home work

Two Stage Strategy (Initial

Structure + 2 Overlays)

2. Overlay (third stage)

1. Overlay (second stage)

Initial Structure

(first sage)

Design Analysis Period

(20 years)

Performance Period

(5 years)

Performance Period

(5 years)


Period (years)

26.9 x 106 -- x 106-- x 106-- x 106W18(ESAL)

????SN ????Thickness


Low Low --Volume Road DesignVolume Road Design


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Low Low --Volume Road DesignVolume Road DesignDesign Chart Procedure


Low Low --Volume Road DesignVolume Road DesignLow Low --Volume Road DesignVolume Road DesignDesign Chart Procedure


Low Low --Volume Road DesignVolume Road DesignDesign Catalog





The Six US Climate Regions








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Low Low --Volume Road DesignVolume Road DesignDesign Chart Procedure


Low Low --Volume Road DesignVolume Road DesignLow Low --Volume Road DesignVolume Road DesignDesign Chart Procedure







The Six US Climate Regions





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Lectures of of 22. . Week 1414. . 09 09 . . 20132013site.iugaza.edu.ps/wp-content/uploads/2_%20Week,%20Stage...Prof. Dr. Eng Shafik Jendia Advantages of Stage Construction 2- Difficulties