Concrete Tie Degradation Study -...

Federal Railroad Administration Office of Research and Development

Concrete Tie Degradation Study Tie Condition and Crack Growth Rate Assessment

Final Results

Funded By Federal Railroad Administration

Office of Research and Development Under Broad Agency Announcement BAA-2010-1

June 5, 2014 Presented by: Jeff Henderson

ENSCO, Inc.


Study Overview • Main Objective

Using machine vision technology, develop a better understanding of concrete tie degradation

• Project Team – FRA Office of Research and

Development – AMTRAK – ENSCO

Sponsored by the Federal Railroad Administration under BAA-2010-1


Technical Approach Overview

1) Image 100 miles of track 3 times over ~1-year 2) Use software to manually align track bed images 3) Grade ties and determine crack growth rates 4) Assess concrete tie degradation over time


Technology Used Hi-rail-based Machine Vision Imaging System

• High Data Rate Line Scan Machine Vision Cameras • High Data Rate Solid State Hard Drives • High-intensity LED Lighting


Track Number

Mile Post Start

Mile Post End

Total Miles

1 187 158 29 1 218 189 29 2 143 158 15 2 187 159 28 2 189 218 29

Total Number of Miles 130

Test Zone Location (Amtrak’s AB Line, Northeast Corridor)


Summary of Test Schedule • Survey 1 – August 16 to 19, 2012 • Survey 2 – April 15 to 19, 2013 • Survey 3 –September 23 to 25, 2013


Concrete Tie Degradation Study Summary of Analysis Approaches

Subjective Analysis • Assess general tie conditions • Evaluate tie degradation based on tie grades

• Grading scale: 1-good to 5-ineffective • Assess a large population of ties ~26,000

Objective Analysis • Use machine vision images to measure crack area • Derive growth rate from measured crack area • Conduct parametric analysis of crack growth rates

• From track charts: Speed, Grade, Curvature, • From other sources: Manufacturer, Crack Size, and

Crack Location


Tie Condition Analysis Types of Conditions Observed

Cracking

Crumbling Erosion Missing Fastener

Chipping


Tie Grading Approach Use software to visually review and grade tie images

Grade 1 – Good Tie

Grade 3

Grade 2

Grade 4 Grade 5 – Ineffective Tie


Crack Growth Rate Determination Use Software to Measure Crack Growth Rate

Unannotated Crack

Survey 1 Annotation

Survey 3 Annotation

Δ Area = 7 mm2

Area 1 = 928 mm2 Area 2 = 935 mm2

Growth Rate = 6.5 mm2 /yr

Annualize the result:


Parametric Analysis Approach Use Statistics to Assess Growth Rates Across

Multiple Crack Populations

0%

20%

40%

60%

80%

100%

120%

0.00

0.03

0.05

0.08

0.10

0.13

0.15

3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 57 60 63 66 69 72 75 78 81 84 87 90 93 96 99 More

Cum

ulat

ive

Freq

uenc

y

Nor

mal

ized

Freq

uenc

y

Annualized Growth Rate (mm^2/yr)

Frequency distributioinCumulative percent curve

• Cumulative percentage is the integral (running total) of normalized frequency • Combines crack growth rate within a population of cracks into a single curve • Provides a means of quantifying crack growth rate over a population of cracks


Tie Condition Results Distribution of Tie Grades

Grade 1

Grade 2

Grade 3

Grade 4

Grade 5

Grade 1 – 97%Grade 2 – 2%

Grade 3 – 0.8%

Grade 4 – 0.2%

Grade 5 – 0.2%

•Distribution based on ~26,000 ties •Typical tie age 33 years

12

Federal Railroad Administration Office of Research and Development 13

Tie Condition Results Distribution of Condition Types

46%

44%

4%6%

CrackChipMissing FastenerCrumbling


Tie Condition Results Percent Change in Number of Tie Grades Over One Year

• Most ties did not advance in grade

• Most ties that did advance in grade did so by 1 grade level

• Relatively few ties advanced by 2 grade levels

• No ties advanced by more than 2 grade levels

-0.23%

0.22% 0.01% 0.00% 0.00%

0.0%

-6.5%

6.2% 0.3% 0.0%

0.0% 0.0%

-3.8%

3.0% 0.8%

0.0% 0.0% 0.0%

-5.8%

5.8%

Grade 1 Grade 2 Grade 3 Grade 4 Grade 5

Gra

de 1

Gra

de 2

Gra

de 3

Gra

de 4

55 Ties 3 Ties

32 Ties 2 Ties

6 Ties 2 Ties

3 Ties

58 Ties

34 Ties

8 Ties


Crack Growth Rates for Total Assessed Crack Population

50%

60%

70%

80%

90%

100%

0102030405060708090

100110

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 More

Cum

ulat

ive

Perc

enta

ge

Freq

uenc

y

Annualized Crack Growth Rate ( mm^2/year)

1386

Measured Growth Rate

Half Normal Distribution

Cauchy Distribution

Cumulative Percentage

• Number of cracks assessed: 2139 • Number that did not grow: 1386 • Number that grew: 748 • Median growth rate: 6.5 mm2/year


Parametric Analysis Results Parameters that Influenced Crack Growth Rate

Parameter Growth Rate of a Typical Crack (mm2/Yr)

Growth Rate Spread (mm2/Yr)

2-Sigma Uncertainty (mm2/Yr)

Residual (mm2/Yr)

Combined Factors Worst case Best case

13 3.8

9.2

2.4

6.8

Crack Size Small crack Medium crack Large crack

4

8.3 7.9

4.3

2.0

2.3

Field VS Gauge Gauge side Field side

8.9 5

3.9

2.1

1.8

Curvature Non-tangent track Tangent track

8.9 5.3

3.6

2.1

1.5

Tie Manufacturer Manufacturer “B” Manufacturer “A”

8.1 5.9

2.2

2.1

0.1


Parametric Analysis Results Parameters that did not Influence Crack Growth Rate

Parameter Growth Rate of a Typical Crack

(mm2/Yr)

Growth Rate Spread

(mm2/Yr)

2-Sigma Uncertainty

(mm2/Yr)

Residual (mm2/Yr)

Posted Speed High range (130 - 150 mph) Low range (30 - 125 mph)

6.5 6

0.5

2.0

-1.5

Grade Neutral Grade (|Grade|≤ .116) Non-neutral Grade (|Grade|> .116)

6.4 6.2

0.2

1.9

-1.7


Impact of Measurement Uncertainty

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 1 2 3 4 5 6

Stan

dard

Dev

iatio

n of

Med

ian

RSS Measurement Uncertainty


Tie Manufacturer Comparison

0.0%

0.2%

0.4%

0.6%

0.8%

1.0%

1.2%

1.4%

1.6%

1.8%

2.0%

2.2%

-52-48-44-40-36-32-28-24-20-16-12-8 -4 0 4 8 12 16 20 24 28 32 36 40 44 48 52

Perc

enta

ge o

f Cra

cked

Tie

s

Approximate Distance from Tie Ceter (inches)

Manufacturer "A"

Manufacturer "B"


Conclusions • The observed crack growth rates were not alarming (median

growth rate = 6.5 mm2/year • Tie grades progressed at a non-alarming rate • Curvature, crack size, crack location (field or gauge side of the

tie), and tie manufacturer had a statistically significant impact on crack growth rates

• Posted speed (track class) and track grade (the degree of incline) did not have a statistically significant impact on crack growth rates

• Tie manufacturer and/or manufacturing lot appears to play an important role in crack prevalence


Remaining Unknowns • The progression rate of failure modes other than cracks (e.g.,

crumbling and chipping) • The impact of tonnage on crack growth rates • The impact of seasonal variations on crack growth rates • The impact of different geographical regions on tie

degradation • Potential variations among additional tie manufacturers


Acknowledgements Federal Railroad Administration Office of Research and Development • Mr. Hugh Thompson – FRA Project Manager • Mr. Cameron Stuart – BAA Program Manager

National Railroad Passenger Corporation (Amtrak) • Mr. Mike Trosino • Mr. Steven Sawadasavi • Mr. Joe Mascara Computer Vision Laboratory at the University of Maryland, College Park • Professor Rama Chellapa • Mr. Xavier Gibert-Serra

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