temperature )induced.curling.of....

Temperature)Induced.Curling.of.Concrete.Crossties

Henry&Wolf,&Riley&Edwards,&Marcus&Dersch,&David&Lange,&Yu&Qian,&

Matt&Csenge,&and&Zhengboyang Gao

FRA.and.FTA.Crosstie.and.Fastening.System.Research. ProgramIndustry.Partners. (IP).Meeting

Tucson,.AZ4.November. 2015

Slide&2Temperature)Induced.Curling.of.Concrete.Crossties

Outline• Background

• Purpose

• Approach

‒ Finite&element&analysis

‒ Laboratory&experimentation

‒ Field&experimentation

• Results&Comparison

• Conclusions


Background• Curling&due&to&temperature&gradients& is&wellOdocumented& in&other&

concrete&infrastructure&applications

– Curling& in&concrete&slabs

• Slab&curling&and&joint&movements&affect&response&of&

pavement&to&traffic&loads

– Camber&in&concrete&bridge&girders

• Can&cause&reOdistribution&of&internal&stresses&in&bridge&

superstructure&and&difficulty&in&construction&


Background.(cont.)• Curling&due&to&temperature&gradients& is&wellOdocumented& in&other&

concrete&infrastructure&applications

– Curling& in&concrete&slab&track

• Slab&curling&causes&loss&of&bond&between&concrete&slab&and&

supporting& layer


Crosstie.Curling.Under.Temperature.Gradient

Small&gap&between&crosstie&

bottom&and&ballast


0

50

100

150

200

250

300

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Center1Negative1Bending1

Mom

ent,1MC=(kip=in)

Center1Support1Factor,1α

Why.it.matters…• Center&negative&crosstie&bending&moments&are&highly&

sensitive&to&small&changes&in&ballast&reaction&at&the&

center&support&region&of&the&crosstie

For&8’O6”&crossties,&

c&=18”

c

1%&&&α 0.8%&&&MCO

25%&&&α 20%&&&&MCO

*.For.62.1.k.rail.seat.load

R R

w wαw


Why.it.matters….(cont.)• If&temperatureOinduced&curl&can&cause&reductions&in&

the&ballast&reaction&at&the&crosstie&center&it&can&lead&to&

decreases&in&center&negative&bending&moment&and&

increases&in&rail&seat&positive&bending&moment

Small&gap&between&crosstie&

bottom&and&ballastCurl


Approach• Perform&literature&review&to&estimate&magnitude&of&

crosstie&curl

• Perform&finite&element&(FE)&analysis&to&confirm&

behavior&and&estimate&magnitude&of&crosstie&curl

• Execute&laboratory&experimentation&to&measure&

magnitude&of&crosstie&curl

– Comparison&with&other&published&values

– Comparison&with&FE&results

• Execute&field&experimentation&to&quantify&revenue&

service&bending&moments&vs.&temperature&gradients


Published.Magnitudes.of.Curl• Compared&published&values&of&curl&for&

concrete&pavements&and&bridge&girders

Temp.Grad..(°F)

MemberLength.(in)

Curl(in)

Curl/Length.(10)4)

Curvature(1/in).(10)6)

Pavement 23O34 120O146 0.039O0.07 2.67O5.83 14.6O38.9

Girder 20 960O1644 0.33O0.76 3.44O4.62 2.3O2.9

Crosstie ? 102 ? ? ?


• Validated&FE&model&has&been&used&to&attempt&to&

predict&and&confirm&these&findings&numerically

• Curl&is&dependent&on&coefficient&of&thermal&

expansion&of&concrete

‒ Use&published&values&– 5.5x10O6&in/&F

Finite.Element.Analysis

�


• Validated&FE&model&based&on&CXT&505S

‒ Includes&ballast&support

• Loading&sequence:

1. Prestress force

2. Temperature&gradient&(30&&F)

3. Vertical&load&(18&k)

Finite.Element.Analysis

�


Finite.Element.Analysis:.Deformed.Shape

Undeformed

After&prestress transfer

30&&F&temperature&gradient

(max&curl&=&1.69x10O2 in)

�

Scale&factor&=&200


Laboratory.Experimentation.to.Measure.Curl

Rail&Seat&A&

Deflection

(δA)

Center&

Deflection

(δC)

Rail&Seat&E&

Deflection

(δE)

Chamfer&Temp.&(TC)

Base&Temp.&(TB)

• Installed&potentiometers&on&rail&seats&and&center&

of&the&crosstie&to&measure&deflection

• Installed&thermocouples&at&chamfer&and&base&of&the&

crosstie&to&measure&temperature


Laboratory.Experimentation.to.Measure.Curl:Set$up

Full&setOup Potentiometer Thermocouple


Laboratory.Experimentation.to.Measure.Curl:.Definitions-and-Calculations

Rail&Seat&A&

Deflection

(δA)

Center&

Deflection

(δC)

Rail&Seat&E&

Deflection

(δE)

Chamfer&Temp.&(TC)

Base&Temp.&(TB)

Curl&=&δC – 0.5(δA +&δE)

Temperature&Gradient&=&TC – TB


Laboratory)Measured.Curl.of.Concrete.Crosstie.Caused.By.Temperature.Gradient.(8/3/15)8/10/15)

!25!20!15!10!50510152025

!6

!4

!2

0

2

4

6

8/3 8/4 8/5 8/6 8/7 8/8 8/9

Temperature5Gradient5(°F)

Warp5(in/1000)

Temperature&Gradient

Curl

Curl

~5.2&in/1000

~O4.5&in/1000

~9.7&in/1000

Date.(2015)


Laboratory.Experimentation.to.Measure.Curl:.Results

Rail&Seat&A&

Deflection

(δA)

Center&

Deflection

(δC)

Rail&Seat&E&

Deflection

(δE)


Max&Curl&=&9.69&in/1000


Laboratory.Experimentation.to.Measure.Curl:Results

Rail&Seat&A&

Deflection

(δA)

Center&

Deflection

(δC)

Rail&Seat&E&

Deflection

(δE)


Max&Curl&=&28.0&in/1000

Max&Curl,&FE&=&16.9&in/1000

Similar&magnitudes,&same&behavior!


Comparison.of.Measured.and.Published.Curl.Values

• Crosstie&curl&and&curvature&are&similar&to&pavements

• Crosstie&curl/length&ratio&is&within&range&of&both&

pavements&and&girders

Temp.Grad..(°F)

MemberLength.(in)

Curl.(in) Curl/Length.(10)4)

Curvature(1/in).(10)6)

Pavement 23O34 120O146 0.039O0.07 2.67O5.83 14.6O38.9

Girder 20 960O1644 0.33O0.76 3.44O4.62 2.3O2.9

Crosstie 29.6 102 0.028 2.75 21.5


Field.Experimentation.Location• Test&site&is&located&in&western&Nebraska

• Concrete&crossties&and&elastic&fasteners&installed&in&1999

• Track&experienced&approximately&220&MGT&of&traffic&in&2014

Test.Site


Field.Site.Layout

Thermocouple

Instrumented&

Crossties&– Zone&2

• Site&split&into&two&zones&of&five&crossties&each

• 50&surface&strain&gauges&installed&on&10&crossties

• Thermocouple&placed&between&zones

Instrumented&

Crossties&– Zone&1


Crosstie Instrumentation• 5&surface&strain&gauges&installed&on&each&crosstie:

– Rail&seat&gauges&(to&measure&rail&seat&positive&

bending)

– Center&gauge&(to&measure&center&negative&bending)

– Intermediate&gauges&(to&measure&asymmetric&

loading&or&support)

B C DA E


Crosstie Instrumentation• 5&thermocouples&installed&on&central&crosstie:

– Ambient&temperature

– Top&of&crosstie&temperature

– Chamfer&temperature

– Ballast/Base&temperature

– Under&crosstie&temperature

B C DA E


Project.Approach

Laboratory calibration

Field data.collection

Data.processing

Conclusions

13.&.14.August.2015

17.September.2015

DatesLaboratory calibration


Strain.to.Moment.Laboratory.Calibration:.Purpose

• Measured&bending&strains&can&

be&converted&to&bending&

moments&through&sectional&

properties,

where,

M&=&bending&moment

E&=&elastic&modulus

I&&&=&moment&of&inertia

ε =&bending&strain

! = #$% &

Bending&strain&(με)

Applied&moment&(kipOin)

1

f&=&EI/y

y&&=&distance&from&neutral&axis

In&concrete,&E&can&varys&

calibration&is&needed


Strain.to.Moment.Laboratory.Calibration:.Procedure

Applied&moment&(kipOin)

Known&moment&applied&with&

Static&Tie&Tester&(STT)&to&

crosstie&in&controlled&loading&

configurations,&record&bending&

strain&and&find&slope&of&curve

Bending&strain&(με)

1

f&=&EI/y

Rail&Seat&Positive Center&Negative


Strain.to.Moment.Laboratory.Calibration:Results

• Used&crossties&of&same&model&and&vintage&(1999)

– Same&model,&same&moment&of&inertia&(I)

– Same&vintage,&similar&elastic&modulus&(E)

• Tested&three&replicates&and&average&calibration&factors

Location Rail.Seat(Gauge A.&.E)

Intermediate(Gauge.B.&.D)

Center(Gauge C)

Calibration factor O768,572.9 615,979.3 504,946.7


Project.Approach

Laboratory calibration

Field data.collection

Data.processing

Conclusions

13.&.14.August.2015

17.September.2015

Dates


Example.Strain.Signal.(Gauge.C)• Strain&peaks&correspond&to&loaded&axles


Bending&Moment&(kipOin)

Example.Bending.Moment.Signal.(Gauge.C)

100

200

• Multiply&strain&by&calibration&factor&to&convert&to&

moment


Example.Thermocouple.Signal• Subtract&chamfer&by&base&to&determine&gradient

85

90

95

100

105

110

115

120

125

130

135

15:00 16:00 17:00 18:00 19:00 20:00

Temperature3(°F)

Time3(MDT)

TopChamferBaseBottomAmbient


Example.Thermocouple.Signal• Subtract&chamfer&by&base&to&determine&gradient

85

90

95

100

105

110

115

120

125

130

135

15:00 16:00 17:00 18:00 19:00 20:00

Temperature3(°F)

Time3(MDT)

TopChamferBaseBottomAmbient

85

90

95

100

105

110

115

120

125

130

135

15:00 16:00 17:00 18:00 19:00 20:00

Temperature3(°F)

Time3(MDT)

ChamferBase

20&°F

O6&°F


!50

!40

!30

!20

!10

0

10

20

30

0

50

100

150

200

250

300

8:00 10:00 12:00 14:00 16:00 18:00 20:00


Bending3Moment3(kip!in)

Time3of3Day3(MDT)

Field)Measured.Average.Center.Negative.Bending.Moments.and.Temperature.GradientsOver.Course.of.Day.(8/13/15.&.8/14/15)

Zone&2

Zone&1

110&kipOin

150&kipOin

30&kipOin60&kipOin


!50

!40

!30

!20

!10

0

10

20

30

40

0

50

100

150

200

250

300

7:30 9:00 10:30 12:00


Bending3Moment3(kip!in)

Time3of3Day3(MDT)

Field)Measured.Average.Center.Negative.Bending.Moments.and.Temperature.Gradients

Over.Course.of.Day.(9/17/15)

Zone&2

Zone&1

160&kipOin

115&kipOin

60&kipOin

30&kipOin


• Curling&behavior&can&be&predicted&with&FE&modelling

‒ Preliminary&analyses&show&similar&curl&(0.017&in&FE&vs.&

0.028&in&measured)

• Curl&in&concrete&crossties&is&within&range&of&published&curl&

for&concrete&pavements

‒ Laboratory&measured&curl&is&0.028&in

• Field&measurements&show&increase&in&temperature&

gradient&causes&decrease&in&center&negative&bending&

moment

‒ 25O30&&F&temperature&gradient&can&cause&30O50%&

reduction&in&center&negative&bending&moment

Conclusions

�


Acknowledgements

• Funding.for.this.research.has.been.provided.by:– National.University.Rail.(NURail).Center,.a.US.DOT)OST.Tier.1.University.Transportation.Center

• Industry&Partnership&and&support&has&been&provided&by

– Union&Pacific&Railroad

– BNSF&Railway

– National&Railway&Passenger&Corporation& (Amtrak)

– Rail&Product&Solutions&(RPS),&Inc.

– GIC&Ingeniería y&Construcción

– Hanson&Professional&Services,&Inc.

– CXT&Concrete&Ties,&Inc.,&LB&Foster&Company

– TTX&Company

• For&assistance&with&finite&element&modelling&and&data&processing

– George&Chen,&Kaijun Zhu,&Phanuwat Kaewpanya,&

Zhipeng Zhang,&Quinn&Todzo,&Max&Silva

FRA.Tie.and.Fastener.BAAIndustry Partners:


Contact.Information

Henry.E..WolfGraduate(Research(Assistantemail:&[email protected]

J..Riley.EdwardsSenior(Lecturer(and(Research(Scientistemail:&[email protected]

Marcus.S..DerschSenior(Research(Engineeremail:&[email protected]

David.A..LangeProfessoremail:&[email protected]


Hypothesis:.Artifact.of.Instrumentation• Installed&an&additional&strain&gauge&near&the&bottom&of&

Crosstie&2&&&Crosstie&9

– Original&gauge&was&exposed&to&sunlight&and&

higher&temperatures

– Additional&gauge&exposed&to&no&sunlight&and&&

lower&temperatures

• Compared&calibrated&bending&moments

Original

Additional


Original.Gauge.vs..Additional.Gauge.MeasurementsCrosstie.9.(7/7/15)

Original

Additional

Original&Gauge

Additional&Gauge

On&average&~10%&difference&for&Crosstie&9&

and&~20%&difference&for&Crosstie&2.

Difference&is&consistent,&most&likely&due&to&

strain&gauge&placement&or&calibration

temperature )induced.curling.of....

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