KENTRACK – A Railway Trackbed Structural Design Program ...
Transcript of KENTRACK – A Railway Trackbed Structural Design Program ...
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KENTRACK – A Railway TrackbedStructural Design Program
Jerry G. Rose & Karthik C. Konduri
University of Kentucky
AREMA 2006 Annual ConferenceLouisville, KY
September 17-20, 2006
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KENTRACKVersion 2.0.1
Railway Trackbed Structural Design Software
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Introduction
Railroads
Track Superstructure
Track Substructure – support system
Research in the last 20 years
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HMA Trackbeds
Overlayment- Ties placed directly over asphalt
- Ballast is only used for cribbing
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HMA Trackbeds
Underlayment- HMA layer present between ballast and subgrade
- Preferred over overlayment
- Better service lifethan overlayment
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HMA Trackbeds
Underlayment
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HMA Trackbeds
Stronger support layerReduced stresses onto subgradeWaterproofing layerNo subgrade pumpingConfining layer for ballast
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Background
Theoritical method Bousinessq’s Elastic TheoryDeficiencies:Assumes the support system to be elastic, isotropic
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Background
Empirical equations- JNR Equation
- Talbot’s Equation
35.11050
hP
P mc +=
25.1
8.16h
PP m
c =
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Background
ILLITRACK- Finite element method- Two dimensionalGEOTRACK- Multilayered theory - Three dimensional model- It was developed to analyze all-granulartrackbeds
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Background
KENTRACKDeveloped specifically to analyze HMA trackbedsHas the versatility to analyze all-granular trackbedsInitially a DOS based programUpgraded to a windows based platform with a Graphic User Interface
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Theory behind KENTRACKSuperposition of Loads
S4
S4
S2
S4
S4
S4
S3 S2
S2
S4
S3 S2 S1
S2S1 S3
7
S3
S1
S2
S2
P1
1 2 3
S4
S1 S2
S3
S3
4 5
P2
6
S3 S2 S1 S2 S3
P
108
P3
9
P4
S4PPS
PPSS 2
41
2'1 +=
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Theory behind KENTRACK
Finite Element Method
w ( P )
y ( M y )
z
y
xji
l
l
w ( P ) z
x ( M x )i
x
jy
R A IL :
T IE :
w ( P )
i
j
S P R IN G :
- To calculate stresses and strains in rail and tie
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Theory behind KENTRACKMultilayered System
En-1 n-1
a
En n
E2
E1
Hzn-2
z2
z
z1
a
qr
- To calculate stresses and strains in the layers
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Theory behind KENTRACK
Material Properties- HMA trackbed is comprised of ballast, HMAand subgrade
- All-granular trackbed is comprised of ballast, subballast and subgrade
- Different equations are used to describe thematerial properties
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Theory behind KENTRACK
Ballast- In a new trackbed it behaves non-linearly- In an aged trackbed it behaves linearly
21
KKE θ=
)21( 0321 Kz ++++= γσσσθ
Subgrade- Linearly elastic material
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Theory behind KENTRACK
Hot Mix Asphalt (HMA)Visco-elastic material
The dynamic modulus of HMA depends on- Temperature- Aggregate passing No. 200 sieve in %- Volume of bitumen %- Volume of air voids %- Asphalt viscosity- Load frequency
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Theory behind KENTRACK
Damage Analysis- Based on minor linear damage analysis
criteria- Performed by periods (seasons, months)
∑=
= n
i da
p
orNNNL
1
1
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Theory behind KENTRACKPredicted number of repetitions
Wheel Load = 36000 lb/wheel
For one car the total weight = 36000 lb/wheel x 8 = 286,000 lb/rep / 2000 = 143 ton/rep
The number of repetitions assumed per year = 200,000 rep/yr
The traffic per year = 200,000 rep/yr x 143 ton/rep = 28,600,000 GT/yr / 1 x 106
= 28.6 MGT/yr
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Theory behind KENTRACK
HMA Damage Analysis- Fatigue cracking controls failure- Fatigue cracking is governed by the tensile strain
at the bottom of HMA- Based on highway experience- Number of allowable repetitions (Na) before failure
853.0291.30795.0 −−= ata EN ε
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Theory behind KENTRACK
Subgrade Damage Analysis- Excessive permanent deformation controls failure- Deformation is governed by the vertical
compressive stresss on top of subgrade- Based on highway experience- Number of allowable repetitions (Nd) before failure
583.3734.3510837.4 +−−×= scd EN σ
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Theory behind KENTRACK
Stresses and Strains
Asphalt Trackbed All-Granular Trackbed
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Methodology
HMA trackbed cross-section
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Methodology
Ballast trackbed cross-section
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Methodology
Critical outputs for the two sections
N/A19.8Service life of HMA (yrs)
5.615.2Service life of Subgrade (yrs)
N/A0.000183HMA Tensile Strain (in/in)
13.811.9Subgrade Vertical Compressive Stress (psi)
Standard Ballast Trackbed
Standard HMA trackbedVariable
Critical Outputs
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Effect of Subgrade Modulus on σc
Axle Load – 36 tons
0
2
4
6
8
10
12
14
16
18
3000 6000 9000 12000 15000 18000 21000
Subgrade Modulus (psi)
Ver
tical
Com
pres
sive
Str
ess (
psi)
HMA TrackbedBallast Trackbed
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Effect of Subgrade Modulus on L
Axle load - 36 tons
0
10
20
30
40
50
60
3000 6000 9000 12000 15000 18000 21000
Subgrade Modulus (psi)
Pre
dict
ed S
ervi
ce L
ife (y
rs)
Subgrade Life in Ballast TrackbedSubgrade Life in HMA TrackbedHMA Life in HMA Trackbed
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Effect of Subgrade Modulus on εt
Axle load – 36 tons
0
0.00005
0.0001
0.00015
0.0002
0.00025
0.0003
0.00035
3000 6000 9000 12000 15000 18000 21000
Subgrde Modulus (psi)
HM
A te
nsile
Str
ain
(in/in
)
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Effect of Axle Load on σc
HMA Trackbed
0
2
4
6
8
10
12
14
16
33 36 39Axle Load (ton)
Subg
rade
Ver
tical
Com
pres
sive
Stre
ss
(psi)
Subgrde Modulus 6000 psiSubgrde Modulus 12000 psiSubgrde Modulus 18000 psi
0
2
4
6
8
10
12
14
16
18
33 36 39
Axle Load (ton)Su
bgra
de V
ertic
al C
ompr
essi
ve S
tres
s (ps
i)
Subgrade Modulus 6000 psiSubgrade Modulus 12000 psiSubgrade Modulus 18000 psi
Ballast Trackbed
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Effect of Axle Load on εt
0
0.00005
0.0001
0.00015
0.0002
0.00025
0.0003
33 36 39Axle Load (ton)
HM
A T
ensi
le S
trai
n (in
/in)
Subgrade Modulus 6000 psiSubgrade Modulus 12000 psiSubgrade Modulus 18000 psi
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Effect of Axle Load on La
05
101520253035404550
33 36 39
Axle Load (ton)
Pred
icte
d Se
rvic
e Li
fe o
f HM
A (y
rs)
Subgrade Modulus 6000 psiSubgrade Modulus 12000 psiSubgrade Modulus 18000 psi
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Effect of Axle Load on Ld
0
10
20
30
40
50
60
33 36 39
Axle Load (ton)
Pred
icte
d Se
rvic
e Li
fe o
f Sub
grad
e (y
rs)
Subgrade Modulus 6000 psiSubgrade Modulus 12000 psiSubgrade Modulus 18000 psi
Ballast Trackbed
0
5
10
15
20
25
33 36 39
Axle Load (ton)Pr
edic
ted
Serv
ice
Life
of S
ubgr
ade
(yrs
)
Subgrade Modulus 6000 psi
Subgrade Modulus 12000 psi
Subgrade Modulus 15000 psi
HMA Trackbed
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Effect of Ballast Thickness
23.3Service life of Subgrade layer
22.37Service life of Asphalt Layer
11.0Compressive Stress on Subgrade
0.000180Tensile Strain in the asphalt
Asphalt Thickness - 8 Ballast Thickness - 6
15.51Service life of subgrade layer
20.42Service life of Asphalt Layer
11.9Compressive Stress on Subgrade
0.000183Tensile Strain in the asphalt
Asphalt Thickness - 6 Ballast Thickness - 8
10.36Service life of subgrade layer
23.77Service life of Asphalt Layer
12.6Compressive Stress on Subgrade
0.000167Tensile Strain in the asphalt
Asphalt Thickness - 4 Ballast Thickness - 10
Asphalt Track Bed Subgrade Modulus 12000 psi, Axle Load 36 ton
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Effect of Ballast Thickness
6.03Service life of Subgrade layer
1.26Service life of Subballast Layer
13.5Compressive Stress on Subgrade
23.4Compressive Stress on Subballast
Subballast Thickness - 8 Ballast Thickness - 6
5.72Service life of subgrade layer
2.13Service life of Subballast Layer
13.7Compressive Stress on Subgrade
20.1Compressive Stress on Subballast
Subballast Thickness - 6 Ballast Thickness - 8
5.56Service life of subgrade layer
N/AService life of Subballast Layer
13.8Compressive Stress on Subgrade
N/ACompressive Stress on Subballast
Subballast Thickness - 0 Ballast Thickness – 14
Ballast Track BedSubgrade Modulus 12000 psi, Axle Load 36 ton
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Predictive Values Versus In-track Data
11.7 / -22.0 / 15.048.7 / -10 / 8
13.6 / -21.0 / 16.047.9 / -10 / 5
Vertical Compressive Stress on Subgrade
KPV/TTD psi
Vertical Compressive Stress on HMAKPV/TTD psi
Vertical Compressive Stress on Ballast
KPV/TTD psi
Thickness Ballast-HMA inches
Comparison of the KENTRACK Predictive values (KPV) Versus In-Track Data (ITD) for the CSX Mainline at Conway, Kentucky
8.2 / 7.721.9 / 114.947.0 / -8 / 8
8.3 / 8.011.7 / 14.943.5 / -12 / 4
Vertical Compressive Stress on Subgrade
KPV/TTD psi
Vertical Compressive Stress on HMAKPV/TTD psi
Vertical Compressive Stress on Ballast
KPV/TTD psi
Thickness Ballast-HMA inches
Comparison of the KENTRACK Predictive values (KPV) Versus In-Track Data (ITD) at TTCI in Pueblo, Colorado
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Summary
KENTRACK is a versatile program that can be used to analyze HMA and all-granular trackbedsHMA trackbeds improve the service life and perform better than all-granular trackbedsDamage analysis values are conservativeSubgrade modulus is a very important factor in trackbed design
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Future Research
Study the aging of HMA in railroad trackbeds. Develop damage analysis equations for HMA and all-granular trackbeds.Attempt to incorporate dynamic factors in the analysis.
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KENTRACK Version 2.0.1
Modified from DOS to Windows with a Graphic User InterfaceValues can be modified easier than the previous versionData files can be opened using the new versionInput and output files can be accessed easily
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KENTRACK Version 2.0.1
Contains:
•Program
•Help File
•Example Data Files
Contact for a copy:
Jerry G. Rose, Ph.D., PE,
Department of Civil Engineering,
University of Kentucky,
Lexington, Kentucky.
40506-0281
(859) 257 – 4278 (Phone)
(859) 257 - 4404 (Fax)
[email protected] (e-mail)
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Questions ?