rigid pavement distresses materials traffic notes

7/25/2019 Rigid Pavement Distresses Materials Traffic Notes

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Distresses in Rigid Pavements, Materials

Characterization and Traffic Analysis

Atul Narayan, S. P.

IIT Madras

September 13, 2015


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Outline

Introduction

Distresses in Rigid Pavements

Materials

Traffic


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Subordinate learning objectives

To analyze the stress-strain distribution in pavements for given

loading conditions.

To estimate pavement distresses based on stresses and

strains in pavement structure.

To explain the effect of mechanical properties on

pavement behavior and performance.

To analyze the stresses and distresses caused by vehicle

loading.

To estimate the expected volume of traffic in design life.


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Outline

Introduction


Materials

Traffic


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Fatigue Model

Fatigue life (PCA/IRC equation):

For

Sc0.55 logNf =11.737 12.077

Sc (1a)

For0.45

Sc0.55 Nf =

4.2577

Sc 0.4325

3.268

(1b)

For

Sc0.45 Nf = + (1c)

where

is the maximum stress in the slab due to the axleload

Scis the modulus of rupture.


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Fatigue Model (cont.)

Fatigue damage is assumed to follow Miners law Damage in rigid pavements is quantified as cracking index.

After considering stresses due to curling, the equation for

cracking index will be as follows:

CI=i

j

k

nijk

Nijk(2)

whereiidentifies the period (month or quarter) in which the

loading occurs,jidentifies the load group and k identifies thecurling condition (day, night or zero temperature gradient)


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Outline

Introduction


Materials

Traffic


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Modulus of Subgrade Reaction

kis determined by loading the subgrade with a circular plate.

In ASTM method, 10 psi pressure is held constant until the

deflection increases by not more than 0.001 in per minute for

three minutes.

As per IS 9214-1974, pressure is increased until a deflection

of 1.25 mm is sustained.

k =p


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Analysis of vehicle loading

The standard axle may cause no damage to certain

pavements. Using EALF does not make sense.

The whole axle loading needs to considered in rigid pavement

analysis, not just the loading on one side of the axle.

Critical stresses need to be determined for the axles.

Edge loading is considered as the critical loading condition to

determine the maximum stress in concrete.


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Edge loading for axles

Single Axles:


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Edge loading for axles (cont.)

Tandem Axles:


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Traffic volume estimation

Design traffic is not estimated in terms of msas.

Traffic volume is presented in axle-load histograms.

For each interval in the histogram, damage cause by numberof axles that belong the interval is computed separately.

Total damage is estimated by summing the damage due to the

number of axles in each interval.

rigid pavement distresses materials traffic notes

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