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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
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