track stiffness measurements and applications€¦ · track stiffness measurements and applications...
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![Page 1: Track Stiffness Measurements and Applications€¦ · Track Stiffness Measurements and Applications Eric Berggren, EBER Dynamics Sweden. Background • Experience – Founder of EBER](https://reader035.vdocuments.site/reader035/viewer/2022062402/5ebd94e2238cda6cf83408bb/html5/thumbnails/1.jpg)
Track Stiffness Measurements and Applications
Eric Berggren, EBER Dynamics Sweden
![Page 2: Track Stiffness Measurements and Applications€¦ · Track Stiffness Measurements and Applications Eric Berggren, EBER Dynamics Sweden. Background • Experience – Founder of EBER](https://reader035.vdocuments.site/reader035/viewer/2022062402/5ebd94e2238cda6cf83408bb/html5/thumbnails/2.jpg)
Background
• Experience– Founder of EBER Dynamics. 2011 --
– Former technical responsible of track measurements at Banverket. 1996 - 2010
– PhD within track stiffness. 2009
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What is vertical track stiffness?
Applied force / track deflection
How much do the rail deflect during a train passage?
–Normal deflection on a new track: 0.5 – 4 mm
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Obvious example of hanging sleepers
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Which parts contribute to deflection?How is track stiffness built up?
Illustration from Selig & Waters 1994
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Track stiffness – complex area
Track stiffness varies with:
– Preload, frequency, dynamic amplitude and position along the track
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Motive for track stiffness measurements:
• Complement to track geometry measurements– Early indications of degradation, better maintenance planning– Hanging sleepers, high sleeper/ballast forces, large rail bending
moments (rail-crack-propagation etc)
• Geotechnical characterization– Stiff/soft tracks– Vibration– Transition zones
• Indicator of root cause at problem sites• Verification
– New track– After maintenance
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Measurement of track stiffness
• Standstill measurements
–Track Loading Vehicle (TLV), Impact hammer, Train passage
• Rolling measurements
–Static (deflection of ordinary wheelset)
–Dynamic (vibration due to oscillating mass)
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RSMV (Rolling Stiffness Measurement Vehicle)
Measurement speed: < 50 km/h
Dynamic load: < 50 Hz, < 60 kN
Static axle load: 180 kN
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RSMV (Rolling Stiffness Measurement Vehicle)
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Dynamic excitation
Acceleration in frequency domainf = v/λ
Several peaks from excitation andtrain-track interaction
- Chose speed – excitation frequencycombination with care
Excitation at 11.4 HzExcitation at 6.8 HzSleeper passing frequency
Vehicle resonance
Test run with speed 40 km/h
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Early example of relevance
9 9.5 10 10.5 11 11.5 120
10
20
30
40
50
60
70
80
Continuous stiffness measurements, West coast line in Sweden, east track w37 2001, 20 km/h 5,7 Hz
Position along the track [ km ]
Stiff
ness [
kN
/mm
]
¯̄
Bridge
Stiffness v = 20 km/h, fEx = 5.7 Hz
No reinforcement
Frostprotection (polyethyren)
pile-deck, bridge
9 9.5 10 10.5 11 11.5 120
1
2
3
4
5
Longitudinal level, rms-value over 20 meters, 2000 - 2001
Position along the track [ km ]
Longitudin
al le
vel [
mm
]
\\tralla
\stiff_
Tra
ckG
eo
me
try
000407
001109
010320
011024
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W 714 W 715
Direction of travel
W 715EW 60-3000/1500-1:18-fb-fakop-r B
ERL
facing move
W 714EW 60-500-1:12-fakop-r B
ERL
trailing move
High speed line Berlin – Hannover (vmax = 200 km/h)
station Buschow (track 6185-1, km 152,4)
ballast track, concrete sleeper
Switches: elastic rip-plate support (ERL),
Support stiffness: ERL: 17,5 kN/mm
Track: Support stiffness: 60 kN/mm
Good example, two turnouts in Germany designed with transition zones
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Bad example from Sweden, tunnel with adjacent turnouts
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Bad example from Sweden, tunnel with adjacent turnouts
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Repeatability and soft soil
40 km/h, 11.4 Hz, 6 repetitive runs
7 km/h, 3 – 20 Hz
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Stiffness phase = Delay of response
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Latest development:EBER Track Lab - ETL
• Multiple measurements close
to loaded axle.
• Eliminate track geometry
• Adjust model to estimate structural parameters– Stiffness
– Damping
– Mass
– Etc.
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Measure track geometry (level) in several positions – at different distance from the load (wheel)
Estimate a deflection curve with a model to relate measurement with structural parameters, as for example:
- Vertical track stiffness- Track damping- Critical velocity - Etc.
EBER Track Lab – Basic idea
𝐸𝐼 𝜕4𝑤(𝑥, 𝑡
𝜕𝑥4 + 𝑚 𝜕2𝑤(𝑥, 𝑡
𝜕𝑡2+ 𝑐
𝜕𝑤(𝑥, 𝑡
𝜕𝑡+ 𝑘𝑤 𝑥, 𝑡 = 𝑄𝛿(𝑥 − 𝑣𝑡
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Track degradation, iron-ore line
Direction of loaded trains
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Critical speed – direct estimate
• The dynamics under a running vehicle will indicate critical speed behaviour well below vcr.
• With a new method, this behaviour can be measured.
• Simulations show adequate estimation of vcr already at the speed of 0.4vcr.
• If used at existing line speeds, the method will give a very good first estimate for the project.
• Tested on known problem sites with good
results
• Main network of Denmark monitored.
20 %
𝑣𝑐𝑟2 =
2
𝑚𝑘𝐸𝐼
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Results from Lammhults mosse
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Lammhultsmosse, ~165 km/h
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Usage in Sweden
• Research measurements– EU-projects
• Inventory before increase of axleload
• Special investigations as regards e.g.– Vibrations
– Soft soils
– USP
– Critical speed
• Initial investigations on relation to track degradation
Main focus has been on geotechnical issues.
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Pros & ConsMethod Pros (+) Cons (-)RSMV (Rolling StiffnessMeasurement Vehicle)
-Dynamic measurements
-Magnitude and phase
-Detailed investigation
-Low speed.
-Require extra loco etc.
-Only fully loaded
EVS (EBER Vertical Stiffness) -At same time as trackgeometry quality.
-Speed.
-Cheap (certainly if combinedwith track geometry)
-Accuracy.
-Calibration
ETL (EBER Track Lab) -At same time as trackgeometry quality.
-Speed.
-More structural parametersthan only stiffness.
-Dynamic characteristicspossible to detect.
-Not fully tested.
-Requires more sensors.
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Conclusions
- Different alternatives for testing- RSMV, EVS, ETL
- Large measurement campaign, speed important
- Static/dynamic properties
- Many examples of usage in Sweden
- Inventory of geotechnical properties.
- Good examples of relation to degrading track, although no one-to-one relationship.