Institute for Road Construction and Maintenance - Vienna University of Technology ISTU O PTIMIZED P...

Institute for Road Construction and Maintenance - Vienna University of Technology

ISTU

OPTIMIZED PAVEMENT DESIGNWITH RESPECT TO

QUALITY AND ECONOMY

Institute for Road Construction and MaintenanceVienna University of Technology

J. Litzka


ISTU

J. LITZKA - OPTIMIZED PAVEMENT DESIGN WITH RESPECT TO QUALITY AND ECONOMY

General objective of pavement design

2

Structural efficiency during the whole design period

Based on given random conditions

- Design traffic load

- Bearing capacity of subgrade

- Material properties of pavement layers


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For routine application (1)

3

Average or minimum values of- Subgrade

- Material properties and fatigue behaviour

Pavement design according to given design traffic (load class)

e.g. catalogue type(like Austrian RVS 3.63, based on analytical calculations)


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For routine application (2)

4

Resulting in a number of technically equivalent pavement solutions

Based on availability of materials and/or on cost comparison the optimal

solution can be selected together with possible alternatives

But still a general solution based on plausible assumptions, not always most cost effective


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J. LITZKA - OPTIMIZED PAVEMENT DESIGN WITH RESPECT TO QUALITY AND ECONOMY 5

Design table RVS 3.63, bituminous pavements


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Possible improvement of economic efficiency (1)

6

Specific analytical design using the underlying procedure for the catalogue, but

Real given values of bearing capacity of subgrade, material characteristics of layers, specific fatigue laws

Also possibility to include new, innovative, not standardised materials


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Possible improvement of economic efficiency (2)

7

Example


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Essential precondition

8

Exact and reliable information about input characteristics

Performance orientated laboratory tests (stiffness modulus, fatigue behaviour etc.)

(t)

(t)

Traffic forecast of high accuracy


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Benefits of specific pavement design

9

Better adaptation to existing subgrade situation

Better utilisation of material properties

Possibility for innovative materials and solutions- Alternative bids

- Performance related contracts


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Further advantage of specific analytical design

10

Stage by stage construction

- Stage 1 as basic solution for first part of design period

- Stage 2 designed based on existing layer properties and realistic design traffic

Better reliability and also acting as maintenance procedure

but: Do not overlook the right moment


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Consideration of costs

11

Construction costs

Life-cycle costs

- Construction

- Maintenance

- Additional user costs (e.g. time loss)

- Environmental costs (possibly)

• Routine• Rehabilitation including

- Traffic management at construction sites- Methods/measures- Intervals


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Calculation of life-cycle costs

12

Prognosis of development of pavement condition necessary

Prediction of life time, change of condition indicator-values and thus prediction of time and type of maintenance measure

Basic tasks for PMS/e.g. VIAPMS


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Change of approach and responsibilities

13

Only construction costs considered

Client chooses contractor according tocost comparison

Sometimes alternatives compared

Actual:

Consider life-cycle costs

At least for road owner costs(construction and maintenance)

New approach (even if normal tender):


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For functional contracts (PPP)

14

Responsibility of concessionaire/contractor to consider

- Complete life-cycle costs

- Including additional user costs(e.g. loss of toll/fee during

rehabilitation works, closures)

Normally compliance with trigger values of pavement condition required


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Functional contracts - example

15

1,5

1,0

2,0

2,5

3,0

3,5

4,0

4,5

5,05

10

15

20

35

technical parameter [mm]

con

dit

ion

in

dex C

I [-

]

0

I

II

III

IV

V

conditionclass

very good

good

fair

poor

very poorThreshold level

Warning level


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Most crucial point: Performance models

16

Standard- type pavements, traditional materials

- Empiric results from database analysis

But still more risks compared with routine application within maintenance

planning- Starting from new pavement

- No calibration of performance models to actual measurements possible


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Most crucial point: Performance models (2)

17

Innovative, new materials and pavements- Prognosis based on analytical calculation

With this also required minimum quality of road condition secured

- First assumption based on existing empiric functions and adaptation by periodic condition measurements (normally required in any case)


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Optimized solution

18

Construction costs

Maintenance costs

including additional user costs

Minimum life-cycle costs

- Most economic solution

- In compliance with given quality requirements


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Development Pavement Condition – Concrete Pavement

19

Concrete Pavement

Bit. Base Course

Subbase

Threshold Level

Warning Level

Exchange of distressed slabs and thin bit. overlay


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Development Pavement Condition – Asphalt Pavement

20

Wearing Course

Bit. Base Course

Subbase

Threshold Level

Warning Level

ReinforcementBase Course

Overlay

Total thickness according to design


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Development Pavement Condition – Asphalt Pavement

21

Wearing CourseBit. Base Course

Subbase

Threshold Level

Warning Level

Reinforcement (2nd construction stage)

Base Course

Overlay

2-stage pavement construction


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Comparison Total Costs (including user costs)

22

Reinforcement(2nd construction stage)

OverlayReinforcement

Replacement of distressed slabs and thin

overlay

Overlay


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Conclusions (1)

23

Increased traffic loads

Limited budgets

Saving of resources

Minimised impact to road users(important for toll roads)

Optimized pavement design necessary with respect to


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Conclusions (2)

24

Improved design methods

Improved materials

Long life, modular pavements

Improved construction quality(very important)

Optimized pavement design possible by applying


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Conclusions (3)

25

Normal contract

Optimized pavement design necessary and possible if

- Administration responsible for design and maintenance

Functional contracts (PPP)

- Concessionaire responsible for design, construction and maintenance over the full concession period together with guaranteed remaining lifetime after termination of contract


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Conclusions (4)

26

Improved, innovative materials

Improved, performance related laboratory tests

High quality of construction

Optimal maintenance organisation

For optimized pavement design necessary in any case

and

Enough time for development of alternative solutions and attributed laboratory tests and calculations during the bidding process


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J. LITZKA - OPTIMIZED PAVEMENT DESIGN WITH RESPECT TO QUALITY AND ECONOMY 27

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