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Field Testing for Understanding

In Situ Concrete Crosstie

and Fastener Behavior

Justin Grassé, David Lange

2012 Joint Rail Conference

Philadelphia, PA

17-19 April 2012

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 2

Outline

• Goals of Field Instrumentation

• Areas of Investigation

• Instrumentation Plan

• Preliminary Data Analysis

• Planned Locations for Field Testing

• Conclusion

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 3

Goals of Field Instrumentation

• Lay groundwork for mechanistic design

of concrete crossties and fasteners

• Map stresses through the fastening system

• Develop an understanding into

probabilistic loading conditions

• Provide insight for future field testing

(AREMA 2010)

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 4

Areas of Investigation Fasteners/ Insulator

• Strain of fasteners

• Stresses on insulator

• Internal strains

– Midspan

– Rail Seat

• Stresses at rail seat

• Global displacement

of the crosstie

Rail

• Stresses at rail seat

• Strains in the web

• Displacements of head/base

Concrete Crossties

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 5

• Understanding of loads

– Vertical

– Lateral

• Reaction at the rail base

• Allowable rail movement

– Translation

– Rotation

• Insulator stresses

• Concrete crosstie stress/ moment distributions

Data Types

• Measures of restraint

– Vertical

– Lateral

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 6

• NI CompactDAQ

– 56+ Channels

• Linear potentiometers

• Strain gages

– Convenional

– Weldable

– Embedment

• Load cells

• Matrix Based

Tactile Surface Sensors

Instruments

NI cDAQ-9188

Strain Gauges Linear Potentiometers

http://www.novotechnik.com/products/linear/linear_potentiometric.html

http://www.ni.com/

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 7

• Linear Potentiometer

Fixture

– Welded steel frame

– Designed for flexible

positioning

– Bolted fastening system

• Lateral Loading Fixture

– Max Capacity ~ 10kips

– Calibration Load ~ 4kips

Instruments

Linear Potentiometer Fixture

Lateral Loader

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 8

Lateral built-up load cell

Chevron patterns

Transverse gages

Strain Gauge Strategy

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 9

Lateral built-up load cell

Strain Gauge Strategy

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 10

Lateral built-up load cell

Strain Gauge Strategy

Curvature:

𝜙 = 𝜀/𝑑

Moments:

𝑀𝑋𝐿 = 𝐸𝐼𝜌𝑋𝐿 = 𝐸𝐼𝜀𝑎 + 𝜀𝑎′

2∙

1

𝑑

d = distance to neutral axis

Shear Force:

𝑉𝑍 = (𝑀𝑋𝐿 − 𝑀𝑋𝑅) ∙1

𝐿

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 11

Chevron patterns

Strain Gauge Strategy

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 12

Chevron patterns

Strain Gauge Strategy

Shear Force:

𝑉𝑍1 =𝐸𝐼

1 + 𝜈 𝑄𝜀1

Total Strain:

𝜀1 = 𝜀𝑎 − 𝜀𝑏 + 𝜀𝑎′ − 𝜀𝑏′

Vertical Load:

𝑃𝑍 = 𝑉𝑍1 − 𝑉𝑍2

=𝐸𝐼

1 + 𝜈 𝑄(𝜀1−𝜀2)

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 13

Transverse gages

Strain Gauge Strategy

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 14

Transverse gages

Strain Gauge Strategy

Curvature:

𝜙 =𝜀

𝑡/2

t = thickness of rail base

Moment:

𝑀𝑋𝐿 = 𝐸𝐼𝜙 =𝐸𝐼𝜀

𝑡/2

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 15

Displacements

• Lateral disp. of the rail base (Dx1)

• Vertical disp. of the rail base (Dz1)

• Vertical disp. of the rail base (Dz2)

• Lateral disp. of the rail head (Dx2)

• Global disp. of the tie (Dzg)

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 16

Preliminary Field Test

• Preliminary Field Investigation at TTCI

• Test Feasibility of Plans/Ideas

• Validate strain measurements

• Gain Familiarity with TTCI

– Facility

– Resources

– Procedures

• Identify “unknowns”

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 17

Strain Gage Location

Safelok I 5 degree curve

Balance Speed = 33mph

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 18

GAUGE

FIELD

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 19

Bending Moments of the Rail

Lateral built-up load cell

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 20

Bending Moments of the Rail M

om

ents

[k-in]

48 398 140 315 315 315 315 315 265 265 [kips]

140k 315k 265k

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 21

Bending Moments of the Rail

Time(s)

10mph

40mph

20mph

Mom

ents

[k-in]

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 22

Bending Moments of the Rail

Time(s)

10mph

40mph

20mph

Mom

ents

[k-in]

Max Moment: 65 k-in

Axle Load: 33 k

Max Moment: 75 k-in

Axle Load: 37 k

Max Moment: 125 k-in

Axle Load: 44 k

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 23

Stress in the Top of the Clips

Instrumented Clip

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 24

Stress in the Top of the Clips

10mph

Str

ess [

ksi]

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 25

Stress in the Top of the Clips

Time(s)

10mph

40mph

20mph

Str

ess [

ksi]

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 26

Stress in the Top of the Clips

Time(s)

10mph

40mph

20mph

Str

ess [

ksi]

Max Stress: 17 ksi

Axle Load: 33 k

Max Stress: 19 ksi

Axle Load: 37 k

Max Stress: 14 ksi

Axle Load: 44 k

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 27

Analysis of Clips

Top Surface of Clips

Field Gauge

After Installation 83 ksi 82 ksi

After Loading 95 ksi 65 ksi

Str

ess [

ksi]

Removal Installation

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 28

Planned Locations for Field Testing

• Monticello Railway Museum

• Transportation Technology

Center (TTC)

– Summer 2012

• Class I Railroads

– Amtrak

– BNSF

– Union Pacific

Transportation Technology Center (TTC)

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 29

Conclusions

• Instrumentation plan will provide synchronized

measurements of:

- Loading conditions

- Allowable Movement

- Component stresses

- Rail seat pressures

• Results will feed into comprehensive FE model

• Strategy will be implemented in variable track

conditions (e.g. fastening systems, curvature) for

parametric analysis

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 30

Acknowledgements

• Funding for this research has been provided by the

Federal Railroad Administration (FRA)

• Industry Partnership and support has been provided by

– Union Pacific (UP) Railroad

– BNSF Railway

– National Railway Passenger Corporation (Amtrak)

– Amsted RPS / Amsted Rail, Inc.

– GIC Ingeniería y Construcción

– Hanson Professional Services, Inc.

– CXT Concrete Ties, Inc., LB Foster Company

• Monticello Railway Museum

– Tim Crouch

• Transportation Technology Center, Inc.

– Dave Davis, Dingqing Li, Ken Lane

• For assistance in instrumentation preparation:

– Sihang Wei, Harold Harrison, Jacob Henschen, Thomas Frankie

FRA Tie and Fastener BAA

Industry Partners:

Field Testing for Understanding In Situ Concrete Crosstie and Fastener Behavior Slide 31

Questions?

Justin Grassé

Graduate Research Assistant

Department of Civil and Environmental Engineering

University of Illinois, Urbana-Champaign

Email: jgrasse2@illinois.edu