Design of CC Pavement - VRVRLatest

8/12/2019 Design of CC Pavement - VRVRLatest

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Prof. VR VINAYAKA RAO

DESIGN OF RIGID

HIGHWAY PAVEMENTS


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5/10/2014 6:59 AM BITS Pilani

CONCRETE PAVEMENT OPTIONS

Jointed Plain Concrete Pavements

Continuously Reinforced Concrete

Pavements

Pre-stressed Concrete Pavement


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FACTORS AFFECTING PAVEMENT DAMAGE

Vehicle

Pavement

Environment

Speed GVW

Pavement type, thickness, roughness

Axle forces Axle and tyre properties


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FACTORS AFFECTING RIGID

PAVEMENT DESIGN

Axle/Wheel Loads

Single Axle10.2t, Tandem19t & Tridem Axle24t

Load Repetitions

Tire Pressure (0.7 to 1 Mpa)0.8 Mpa

Thickness > 20Cm Tire Pressure need notbe considered

Lateral Placement of the Axles


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FACTORS AFFECTING RIGID

PAVEMENT DESIGN (Contd..)

Unpredicted Heavy Truck Movements

Load Safety Factor (1.2, 1.1 & 1.0 for three

hierarchies of roads)

Design Axle Load98thPercentile

Design Period (15 to 30 Years)

Design Traffic: IRC 9Traffic Census

Tire Tangential to Longitudinal Edge - Critical


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FACTORS AFFECTING RIGID PAVEMENT

DESIGN (Contd..)

Fatigue 25% of Two-Lane Two-Way CommercialVehicles (Design Traffic)

Four or Multi Lane Highways25% ofCommercial Vehicles in the Predominant

Direction

CSA = [365 * A * {(1+r)n1}] / r

Temperature Differential = f(Solar Radiation received,

Thermal Diffusibilityof CC, Losses Due to Wind

Velocity etc.)

Table 1 - IRC 582002 (Six Different Regions in India)


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CHARACTERISTICS OF SUB-GRADE & SUB-BASE

Modulus of Sub-grade Reaction (K) Pressureper Unit Deflection of Foundation @ LimitingDeflection

Limiting Deflection1.25mm

Plate Diameter75cm

K75= 0.5 x K30

CBRK Correlations (Tables 2, 3 & 4)

125 Micron thick Polythene Layer between CCand DLC Layers to Reduce Interlayer Friction

Drainage Layer above Sub-grade


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FACTORS AFFECTING RIGID PAVEMENT DESIGN

(Contd..)

Characteristics of Concrete

Design Strength

S = Target Ave. Flexural Strength @ 28 days= S+ Za

S = Characteristic Flexural Strength @ 28 Days

Za = Tolerance Factor for Desired ConfidenceLimits (Table 5IRC 58)

= Expected Standard Deviation of FieldSamples (IS 4562000)


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(Contd..)

Flexural StrengthMR Test3rdPoint LoadingIS 516

Aggregate Size > 19mm - 15x15x70 Cm

Aggregate Size < 19mm - 10x10x50 Cm Flexural Strength4.5 Mpa

E = 3 x 105Kg/Cm2

PoissonsRatio = = 0.15 Coefficient of Thermal Expansion

= 10 x 10 6/ oC


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(Contd..)

Fatigue Behavior of CC (MinorsHypothesis)

Stress Ratio (SR) = Flexural Stress / Flexural Strength

N = Unlimited for SR < 0.45

N = [4.2577 / (SR - .4325)]3.268for 0.45


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JOINTED PLAIN CEMENT

CONCRETE PAVEMENT

Most Popular Rigid pavement Option

Maintenance Costs increases with theincrease in the joint spacing

Maximum joint spacing should be 12.2m


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CONTINUOUSLY REINFORCED

CEMENT CONCRETE PAVEMENT

Elimination of Joints Reducedthickness

Thickness of CRCP Will Workout to be 70-80% of the conventional pavement.

Cracks are held tightly by the reinforcement

Punch-outs are the major type of distress

Design equations for JRCP can be used forCRCP


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PRESTRESSED CONCRETE PAVEMENT

Concrete is weak in Tension, strong in

compression

Thickness is governed by modulus of rupturewhich varies with the tensile strength of

concrete

Pre-application of compressive stressreduces the tensile stresses caused by trafficloads, decreases the thickness

Less probability of cracking and fewertransverse joints, less maintenance andlonger life


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PRESTRESSED CONCRETE PAVEMENT

Slab Length Varies from 90 to 232m Slab Thickness 152mm (Maximum)

Post tension method is Frequently Adopted

More Frequently used for Airport Pavements,Saving in Thickness

Thickness of Pre-stressed Highway Pavement

will be Sufficient Enough to Provide Cover forthe Pre-stressing Steel

Still in the Experimental Stage


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RIGID HIGHWAY PAVEMENT DESIGN

Guidelines for the Design of Plain JointedRigid Pavements for Highways IRC: 582002,2011

AASHTO Method, 1993

PCA Method

ACI Method


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IRC: 582002 METHOD OF

RIGID PAVEMENT DESIGN

Guidelines cover the design of Plain

Jointed cement concrete pavements with

or without dowels

Applicable to roads having a daily

commercial traffic (vehicles with laden

weight exceeding 3T) of over 150


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NEW FEATURES OF IRC: 58 - 2002

Computation of Flexural stress due to

placement of single and tandem axle

loads along the edge

Introduction of the cumulative fatigue

damage approach in the design

Revision of criteria for design of dowel

bars


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CRITICAL STRESS CONDITION

Additive Flexural Stresses due to Load andTemperature DifferentialsCritical

Tandem Axle Causes 20% lesser load than singleaxles Super Position of Negative Bending

Moment due to one dual wheel over the other Average Spacing of Tandem Axles1.31m

Curling - Top Convex during Day and TopConcave during the Night

Corner Discontinuous in 2 Direction MoreCritical

CornerTemp. Stress is Negligible


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CRITICAL STRESS CONDITION

Temp Stresses will be Maximum during the day

when there is maximum temp. differential at

Edge and Interior Regions

Night Critical for Corner Region Corners

tending to warp up

Corner Critical No Dowel Bars are Provided

Corner Critical Aggregate Interlock is Absent


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CALCULATION OF STRESSES

EDGE STRESSES

Due to Load: Westergaards and Pickett & RaysChart TechniquesIITRIGID.EXE

Appendix 1 for Different Single and TandemAxle Loads (Stresses have been Given)

Westergaards Equation Modified by Teller andSutherland are not Applicable for Different WheelConfigurations and hence not Useful


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EDGE STRESS

Due to Temperature: Westergaards

Equation using BradburysEquation

Ste= E t C / 2.0Figure 2 for Bradburys Coefficient as wellas Stress Values



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CORNER STRESS

Westergaard's Equation (Modified by Kelly)

Scl= (3P/h2) * { 1 (a2/l)1.2} (kg/Cm2)

a = Radius of Equivalent Circular ContactArea (Cm)

l = Radius of Relative Stiffness (Cm)

= [(Eh3)/{12(1-2)K}] 0.25


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STRESS RATIO AND FATIGUE ANALYSIS

Cumulative Fatigue Damage for

Different Axle Loads shall be Less than1.0

Procedure for Cumulative Fatigue

Damage is Given in Appendix 2 of

IRC 58 - 2002


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EROSION CONSIDERATION

& HARD SHOULDERS

Multi Axle Vehicles Usually Cause Erosion at theBottom of the Pavement

To Prevent, Paved Shoulder Shall be Extended by

1.5m beyond the Pavement DLC Shall be Extended by 40 to 50 Cm towards the

Shoulder

In addition, Full Depth Bituminous Shoulder or tiedCC Shoulder Shall be Constructed to ProtectPavement Edge

Anchor Beam and Terminal Slab


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IRC: 582002 DESIGN PROCEDURE

Stipulate design values for the variousparameters

Decide types and spacing between joints

Select a trial design thickness ofpavement slab

Compute the repetitions of axle loads ofdifferent magnitudes during the designperiod


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Calculate the stresses due to single andtandem axle loads and determine thecumulative fatigue damage (CFD)

If the CFD is more than 1.0, select a higher

thickness and repeat the above steps

Compute the temperature stress at theedge and if the sum of the temperature

stress and the flexural stress due to thehighest wheel load is greater than themodulus of rupture, select higherthickness and redesign


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Design the thickness on the basis of

corner stress if no dowel is provided

and there is no load transfer due to lack

of aggregate interlocking

Design Dowel and Tie Bars if necessary


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ILLUSTRATION OF IRC 58-2002

DESIGN OF RIGID PAVEMENT

EXAMPLE

Two Lane Two Way Highway

Location: Karnataka State

Total Two Way Traffic = 3000 CVPD

Flexural Strength of Concrete = 45 Kg/Cm2

Effective K with DLC = 8 Kg / Cm2

E of Concrete = 3 x 105Kg / Cm2


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Single Axle Loads Tandem Axle LoadsAxle Load

Class (t)

% of Axle

Loads

Axle Load

Class (t)

% of Axle

Loads

19-21 0.6 34-38 0.3

17-19 1.5 30-34 0.3

15-17 4.8 26-30 0.6

13-15 10.8 22-26 1.8

11-13 22.0 18-22 1.59-11 23.3 14-18 0.5


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Present Traffic = 3000 CVD

Design Life = 20 Years

r = 0.075

Cumulative Repetitions

= 3000*365*[{(1.075)201}/0.075]

= 47,418,626 CV

Design Traffic = 0.25 * 47,418,626

= 11,854,657 CV


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Single Axle Loads Tandem Axle LoadsLoad in

Tonnes

Expected

Repetitions

Load in

Tonnes

Expected

Repetitions

20 71127 36 35564

18 177820 32 35564

16 569023 28 71128

14 1280303 24 213384

12 2608024 20 177820

10 2762135 16 59273


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Trial Thickness = 32 Cm

Sub-grade Modulus = 8 Kg/Cm3

Design Period = 20 Years

Modulus of Rupture = 45 Kg/Cm2

Safety Factor = 1.2


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Axle Load

(t)

AL * 1.2 Stress

(Kg/Cm2)

Stress

Ratio

Expected

Repetitions

(n)

Fatigue

Life N

Fatigue Life

Consumed

1 2 3 4 5 6 Ratio (5/6)

Single Axle

20 24.0 25.19 0.56 71127 94100 0.76

18 21.6 22.98 0.51 177820 485000 0.37

16 19.2 20.73 0.46 569023 14330000 0.04

14 16.8 18.45 0.41 128030 Infinite 0.00

Tandem Axle

36 43.2 20.07 0.45 35560 62800000 0.000632 38.4 18.40 0.40 35560 Infinite 0

Cumulative Fatigue Life Consumed 1.1706


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Axle

Load (t)

AL *

1.2

Stress

(Kg/Cm2)

Stress

Ratio

Expected

Repetitions(n)

Fatigue Life

(N)

Fatigue Life

Consumed

1 2 3 4 5 6 Ratio (5/6)

Single Axle

20 24.0 24.10 0.53 71127 216000 0.33

18 21.6 21.98 0.49 177820 1290000 0.14

16 19.2 19.98 0.44 569023 Infinity 0.00

14 16.8 17.64 0.39 128030 Infinity 0.00

Tandem Axle

36 43.2 19.38 0.43 35560 Infinity 0.00

Cumulative Fatigue Life Consumed 0.47

Trial Thickness = 33 Cm


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Check for Temperature Stress

Edge Warping Stress (Ste) = E t C / 2.0= 17.3 Kg/Cm2

( For L = 450Cm, B = 350 Cm, l = 103.5, L/l = 4.4 & C = 0.55from Fig. 2 & Temp. Diff. = 21oC )

Total of Load (Highest) and Warping Stress = 24.10 + 17.3

= 41.4 Kg/Cm2

< 45 Kg/Cm2 Hence Safe


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Check for Corner Stress due to Load

Scl= (3P/h2) * { 1(a2/l)1.2}

98 Percentile Axle Load is 16 Tonnes

The Wheel Load = 8 Tonnes

Radius of Relative Stiffness( l ) = 103.5 Cm


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Radius of Contact of Wheel (a)

(Single Axle Dual Wheel)

a = [0.8521 * (P)/(q*)* (S/ )*{(P) / 0.5227*q}0.5]0.5P = Load

S = C/c Distance between Two Tires

q = Tire Pressure

a = 26.51 Cm




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Corner Stress due to Load = 15.52 Kg/Cm2

Flex. Strength of Concrete = 45 Kg/Cm2

Hence the Proposed thickness of 33 Cm is safe

since Corner Stress Due to Load is Less than

the Flexural strength of Concrete


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AASHTO DESIGN PROCEDURE

Design of Slab Thickness

Estimate future Traffic

Reliability ( R )

Overall Standard Deviation (So) Design Serviceability Loss

Concrete Elastic Modulus (Ec)

Concrete Modulus of Rupture (Sc

) Load Transfer Coefficient (J)

Drainage Coefficient ( Cd)


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Reliability

Accounts for the changes in variation in both trafficprediction and performance prediction

50 - 805080Local

75 - 958095Collectors

75 - 958099Principal Arterials

8099.985 - 99.9Interstate and other

Freeways

RuralUrban

Recommended Levels of ReliabilityFunctional

Classification


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Overall Standard Deviation ( So)

Rigid Pavement 0.35

Design Serviceability Loss

PSI Ranges from 5 (Perfect road) to 0

(Impossible Road)

Index of 2.5 for Design of Major Roads and 2.0

for Less Important Roads

Initial Serviceability for Rigid Pavements4.5


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Concrete Elastic Modulus

Concrete Modulus of Rupture

Sc

= Sc+ Z (SD

s)

Where Sc= Estimated mean value for PCC

modulus of rupture (psi)

Sc= Construction specification on concrete

modulus of rupture

SDs= Estimated standard deviation of concretemodulus of rupture


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Z = Standard normal variate

0.841 for PS = 20%

1.037 for PS = 15%

1.282 for PS = 10%

1.645 for PS = 5%

2.327 for PS = 1%


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Load Transfer coefficient (J)

Factor accounts for the ability of the

concrete pavement to transfer load

across joints

J = 3.2 for JCP and JRCP, with some

type of load transfer device

J = 3.8 to 4.4 when there is no load

transfer device


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PCA DESIGN OF RIGID PAVEMENTS

Flexural strength of Concrete (Modulus ofRupture MR)

Strength of the subgrade or subgrade and

subbase combination (K) The weights, frequencies and types of truck axles

loads that the pavement will carry

Design period, which in this and other pavementdesign procedures is usually taken at 20 years,

but may be more or less


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PCA DESIGN PROCEDURE

Type of Joint and Shoulder Concrete Flexural strength (MR) at 28 days

K value of the subgrade or subgrade and

subbase combination

Load safety factor (LSF)

Axle load distribution Expected number of repetitions



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Fatigue analysis to control fatigue cracking

and erosion analysis to control foundationand shoulder erosion, pumping, and faulting

Fatigue analysis will usually control the

design of light traffic pavements andmedium traffic pavements with doweledjoints

Erosion analysis will usually control the

design of medium and heavy trafficpavements with undoweled joints and heavytraffic with doweled joints



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For pavements carrying normal mix of truck

types, single-axle loads are usually more severein the fatigue analysis, and tandem axle loads aremore severe in the erosion analysis

Fatigue Analysis

Assume Trial Thickness and Equivalent StressFactor depending on the Trial Thickness and KValue

Estimate the Expected and AllowableRepetitions

The Ratio of Expected to Allowed Should Notbe More than 100%


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Erosion Analysis Assume trial thickness and the equivalent

stress factor depending on the trial

thickness and k value

Estimate the expected and allowable

repetitions

The ratio of expected to allowed should notbe more than 100%

Documents

Design of CC Pavement - VRVRLatest