A New A New Real-Time, Non-Contact Real-Time, Non-Contact

Transfer-Length Measurement TechniqueTransfer-Length Measurement Technique

Dr. Terry Beck (Mechanical Engineering)Dr. Terry Beck (Mechanical Engineering)

Dr. Robert Peterman (Civil Engineering)Dr. Robert Peterman (Civil Engineering)

Dr. John Wu (Industrial Engineering)Dr. John Wu (Industrial Engineering)

Weixin Zhao (Industrial Engineering)Weixin Zhao (Industrial Engineering)

Inventors:Inventors:Inventors:Inventors:

What is the problem for which you have a solution ?

What is the problem for which you have a solution ?

Why Measure Transfer Length?Why Measure Transfer Length?

• Used for calculation of shear capacity• Used for calculation of stresses• Has been shown to often be a good indicator

of strand development length• Could be used as a tool to screen out

potentially poor-bonding mixes

How is the problem being solved now?

 What’s wrong with current solutions?

We simply don’t measure it?

Why Don’t We Measure Transfer Length at the Present Time?

Why Don’t We Measure Transfer Length at the Present Time?

• There is currently not a convenient or time-efficient method to get this information

• The current method(s) interrupt the daily casting and de-tensioning sequence

Current Tool

Whittemore Gauge

4 8 M P a ( 7 K S I ) S L W S p e c im e n w i t h 1 /2 " - S p e c ia l F W C S t r a n d

- 1 8 0 0

- 1 6 0 0

- 1 4 0 0

- 1 2 0 0

- 1 0 0 0

- 8 0 0

- 6 0 0

- 4 0 0

- 2 0 0

0

0 2 0 4 0 6 0 8 0 1 0 0

D is t a n c e A lo n g B e a m ( c m )

Mic

rost

rain

A t T r a n s f e r o f P r e s t r e s s

3 D a y s A f te r T r a n s f e r

1 4 D a y s A f te r T r a n s f e r

3 6 D a y s A f te r T r a n s f e r

6 6 D a y s A f te r T r a n s f e r

00 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0 2 5 0 0

D i s t a n c e A l o n g B e a m ( m m )

4 8 M P a ( 7 K S I ) S L W S p e c im e n w i t h 1 /2 " - S p e c ia l F W C S t r a n d

- 1 8 0 0

- 1 6 0 0

- 1 4 0 0

- 1 2 0 0

- 1 0 0 0

- 8 0 0

- 6 0 0

- 4 0 0

- 2 0 0

0

0 2 0 4 0 6 0 8 0 1 0 0

D is t a n c e A lo n g B e a m ( c m )

Mic

rost

rain

A t T r a n s f e r o f P r e s t r e s s

3 D a y s A f te r T r a n s f e r

1 4 D a y s A f te r T r a n s f e r

3 6 D a y s A f te r T r a n s f e r

6 6 D a y s A f te r T r a n s f e r

00 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0 2 5 0 0

D i s t a n c e A l o n g B e a m ( m m )

Strain in Pretensioned Concrete Member

What is our solution? What is our solution?

• Non-Contact Measurements

• Portable as Current Tool

• Much Higher Precision

• More Flexible

Surface Film Planeor Detector

Coherent LightSource

In Phase-Bright Speckle

Out of Phase-Dark Speckle

Concept of Laser Speckle

Photograph of Laser Speckle on Concrete

Peak Distances vs. Strains Measures

0.02mm deflection 0.10mm deflection 0.20mm deflection

Actual experimental work

we have performed? Actual experimental work

we have performed?

Concrete beam cutting experiment

Prototype Design

Experiment SetupBeam Cutting

Cutting Pretensioned Specimen

Comparison of Different Strain Gauges

Right Side

-50.0

0.0

50.0

100.0

150.0

200.0

0 20 40 60 80 100

Distance along beam(cm)

Mic

ros

tra

in

Whittemore 11-16

Optical 11-16

Diode Laser

Beam Expander

Speckle Pattern Images

CCD Camera

Mirror

Mirror

Mirror

Tested Surface

50/50 Beam Splitter

Strain

The New Device

Prototype Specification

41/4 inches

8 in

Resolution: < 10m

Weight: 3 lbs

Dimension: 11”x6”x4”

Measurement speed: 15 samples/second

Optical Sensor

Concrete Cylinder Compression Experiment

Electronic Strain Gage

Optical Strain Gage

Concrete Cylinder Results

0

50

100

150

200

250

300

350

400

450

500

0 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000

Load (lbs)

Mic

rost

rain

ESG at surface 1

Optical at surface 1

Concrete Cylinder Results

Differences Between Optical and ESG

-4

-3

-2

-1

0

1

2

3

4

5

6

7

0 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000

Load (lbs)

Mic

rost

rain

What is the closest prior art that might be

cited against the novelty of your invention?

None !

What Still Needs to Be Done?

• Continue to Gather SCC Mix Ingredients

• Cast Pretensioned Transfer-Length Specimens Members from 5 mixes used in SCC bond study

• Compare Whittemore Gage Results with Optical Results

Additional K-State PersonnelHave Been Added

• Commercialization Manager.

• 2 MBA Students (Final Project).

• Product Design Engineer.

• 2 Other Design Engineers (Optics and Electrical).

• Precision Optical Measurements, Inc.

The Goal

• Version 1 available for use this summer.

• For sale within one year (Approx. $20k)

The Future

Measurement Surface

Traverse

Sensor

Auto Measuring System

Delta Strain Rosette

Who specifically would be a possible commercial partner or

licensee for your invention?

•Precision Optical Measurement Inc.

•Advanced Manufacturing Institute

Questions?