Deflection Testing marketing1.ppt

An Introduction to Deflection

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An Introduction to Deflection Testing

Reuben Williams, P.E.

November 15, 2011

Outline

� History of deflection testing

� What is an FWD?

� How does it work?

� Different uses

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� Different uses

� Data from testing

� Analysis

� Limitations

� Advantages

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There are two broad categories:

� Static devices� Dynamic devices

� Vibratory� Impulse

History

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� Impulse

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What is an FWD?

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What is an FWD?

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How does it work?

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Uses

� Structural Testing/Remaining Life

� Joint Load Transfer

� Void Detection

� Load Restrictions

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� Load Restrictions

� Super Heavy Load (Evaluation/Permits)

� Project Acceptance

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Uses - Layer Moduli

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1.1. Apply axial loadApply axial load2.2. Measure axial Measure axial

deformationdeformation3.3. Compute Modulus Compute Modulus

“E” “E”

δσ / =E

1.1. Apply FWD loadApply FWD load2.2. Measure Surface Measure Surface

deflectiondeflection3.3. Compute ModulusCompute Modulus

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Uses - Load Transfer Efficiency

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Uses - Void Detection

0

2

4

6

8

10

12

14

16

18

Deflection (m

ils)

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0

0 2000 4000 6000 8000 10000 12000 14000 16000 18000

Station (feet)

Sensor 1 Sensor 2 Sensor 3 Sensor 4 Sensor 5 Sensor 6 Sensor 7

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Uses - Void Detection

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Uses – Load Restrictions/Super Heavy Loads

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Data

� Load and deflection readings

� Surface and Air Temperatures

� Additional measurements of HMAC layer temperature

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Analysis

Objective

Determine Layer Moduli

Determine LTE Identify Voids

Plot Deflection ProfilePlot the deflection under the load plate against the

measured load.

∗= 100

L

ULTE

δ

δ

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Select Sampling Locations

Sampling

Lab Testing

Backcalculation of Layer Moduli

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Analysis – Additional Information Required

�Layer Thickness

�Material Types

�Moisture Contents

�Shallow bedrock layer

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AC/PCC

Base

Subgrade

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Analysis – Profile Plots

Runway 15/33 - Pass 1

10 ft Right of CL

16 kip Load

50

60

70

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0

10

20

30

40

50

0 1000 2000 3000 4000 5000 6000 7000 8000

Station (feet)

De

fle

cti

on

(m

ils

)

Sensor 1 Sensor 2 Sensor 3 Sensor 4 Sensor 5 Sensor 6 Sensor 7

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Analysis – Profile Plots

Runway 15/33 - Pass 1

10 ft Right of CL

16 kip Load

Sensor 7

3.5

4

4.5

5

Defl

ecti

on

(m

ils)

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0

0.5

1

1.5

2

2.5

3

0 1000 2000 3000 4000 5000 6000 7000 8000

Station (feet)

Defl

ecti

on

(m

ils)

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Analysis – 2-D Profile Plots

200

250

300

FW

D T

es

t S

tati

on

(ft

)

Apron Area 1

16-kip Load, Sensor 7 Deflection (mils)N

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050100150200250300350400450500550

0

50

100

150

Pass Offset (ft)

FW

D T

es

t S

tati

on

(ft

)

0-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8

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Analysis - Material information

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Analysis – Backcalculation

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Cost Comparison

Item Quantity UnitsAverage Unit

PriceCost

Cores/Bores 32* cores $300/core $9,600.00

Traffic Control 3 days $1000/day $3,000.00

Destructive Testing

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Atterberg 32 tests $ 55.00/test $1,760.00

Gradations 32 tests $ 55.00/test $1,760.00

Moisture

Contents32 tests $ 15.00/test $480.00

Total $16,600.00

* 1hole every 500 ft

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Cost Comparison

Item Quantity UnitsAverage Unit

PriceCost

FWD Testing 8 hours $250/hour $2,000

Traffic Control 2 days $1000/day $2,000Cores/Bores 8 samples 300 $2,400

Atterberg 8 tests $ 55/test $440

NDT and Destructive Testing - 3 lane miles, 158 data points

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Atterberg 8 tests $ 55/test $440

Gradations 8 tests $ 55/test $440

Moisture

Contents8 tests $ 15/test $120

Analysis of

FWD Data8 hours $100/hour $800

Total $8,200

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Cost Savings

50,000 ESALs 5,000,000 ESALs 50,000,000 ESALs

3,000 2.77 5.80 8.08

5,000 2.28 4.92 6.97

7,000 1.99 4.39 6.31

50,000 ESALs 5,000,000 ESALs 50,000,000 ESALs

SN RequirementsSubgrade

Modulus, psi

Subgrade

Modulus, psi

Difference in HMAC Thickness, in

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50,000 ESALs 5,000,000 ESALs 50,000,000 ESALs

5,000 1.11 2.00 2.52

7,000 1.77 3.20 4.02

* Assuming a design modulus of 3,000 psi

50,000 ESALs 5,000,000 ESALs 50,000,000 ESALs

5,000 15,244 27,378 34,533

7,000 24,267 43,867 55,067

* Assuming a design modulus of 3,000 psi

Modulus, psi

Subgrade

Modulus, psi

Cost Savings/mi, $

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Limitations

� Shallow bedrock

� Interpreting results

�Temperature

�Moisture

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� Model dependencies of analysis tools

�Load Application

�Material Characterization

� Temperature at time of LTE testing

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Advantages of FWD Testing

�� Nondestructive testNondestructive test

� Simulates Response of Moving Wheel

�� In Situ response of pavement layersIn Situ response of pavement layers

�� Better coverageBetter coverage

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�� Better coverageBetter coverage

�� Expediency in data collectionExpediency in data collection

�� Reduced evaluation costs Reduced evaluation costs

�� Reduced construction costsReduced construction costs

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Summary

� History of deflection testing

� What is an FWD?

� How does it work?

� Different uses

� Data from testing

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� Data from testing

� Analysis

� Limitations

� Advantages

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Questions

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