University of Wollongong
Remaining Life of Concrete
Sleepers: A Multifaceted
Approach
A/Prof Alex Remennikov
School of Civil, Mining and Environmental Engineering
University of Wollongong, NSW, Australia
1
Introduction
 This project will give track owners methods of more
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accurately assessing the dynamic capacity of in-track
concrete sleepers.
 As commercial pressures drive up axle loads and train
speeds, deferring large-scale sleeper replacement through
higher sleeper capacity rating has the potential for very
large savings in capital expenditure for owners.
 To establish better methods of sleeper rating, the method is
based on in-track and laboratory-based studies of the static,
dynamic and impact behaviour of sleepers, of the actual
loading regimes experienced by sleepers in-track, and
detailed material characterization of the concrete.
Strength
Loading
Materials
3
•
•
•
•
Static tests
Impact tests
Fatigue tests
Prestressing tests
•
•
•
•
Processing of WILD data
Spectral analysis of WILD
Forecasting for next 5-10 years
Limit states design checks
• Concrete strength
• Cement content/w/c ratio
• Ultrasonic Pulse Velocity
• Concrete carbonation
• Sulphate Attack and Delayed
• Ettringite Formation
Collection and Processing of
Wheel Impact Detectors Data
Spectral Analysis of Data from
WILD
Extrapolation of data for next
5-10 years period
Limit States Design Checks
Typical wheel impact detector (WID) data
as-received
5
Static loads (extracted from WID data)
6
Impact loads (extracted from WID data)
7
Impact load curve fitting
1:10
1:100
1:1000
8
Impact load, forecasting
9
Static bending testing
Dynamic impact testing
Fatigue testing
Prestressing tests
STATIC TESTS
Rail seat vertical load tests – Negative and Positive Bending Moments
Centre Negative and Positive Bending Moment Tests
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DYNAMIC TESTING
Concrete Sleepers Impact Load Testing Facility at UoW
Characteristics:
• Height of impact = 6 m
• Weight of anvil = 600 kg
• Max impact velocity = 10 m/s
• Max impact energy = 10,000 J
• Max impact load = 2000 kN
Monitoring equipment:
• Dynamic load cell
• Laser displacement sensors
• Accelerometers
• Strain gauges
• High-speed camera
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12
DYNAMIC TESTING
Impact tests setup
Optical
trigger
Falling anvil 600 kg
Shock
absorbers
Sleeper
support
system
Strong
floor
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13
Tested
concrete
sleepers
DYNAMIC TESTING
Impact tests setup – sleepers support systems for different track moduli
Very soft track (8 MPa)
Moderate track modulus
(20-70 MPa)
Very hard track (120 MPa)
Ballast (200 mm)
Sand-rubber Mix (200 mm)
Strong Concrete Floor
(1.5 m deep)
Shock mat
(10mm)
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Ballast (150 mm)
Strong Concrete Floor
(1.5 m deep)
Shock mat
(10mm)
VERIFICATION OF PRESTRESSING
Test arrangement and instrumentation
Specimens prepared for dynamic
relaxation tests at sleeper centre
Strain gauges attached to
steel wires
Wire cutting
and data
recording
procedure
15
15
TYPICAL RESULTS – STATIC TESTING
Rail Seat Bending Strength
600
UOW5
UOW6
Total load (kN)
500
400
300
200
100
0
0
4
8
12
Displacement (mm)
16
20
8
12
Displacement (mm)
16
20
500
UOW7
UOW8
Total load (kN)
400
300
200
100
16
16
0
0
4
TYPICAL RESULTS – STATIC TESTING
Centre Bending Strength
120
UOW1
UOW2
Total load (kN)
100
80
60
40
20
0
0
10
20
Displacement (mm)
30
40
150
UOW3
UOW4
Total load (kN)
120
90
60
30
0
17
17
0
10
20
30
Displacement (mm)
40
50
TYPICAL SUMMARY OF STATIC TEST
RESULTS
1
2
3
4
1818
Type of test
Sleeper Cracking Cracking
marks load
moment
(kN)
(kN.m)
30.0
Ultimate
load
capacity
(kN)
99
Ultimate
moment
capacity
(kN.m)
38
Centre positive
moment (MC+)
UOW1
78
UOW2
85
32.6
99
38
Centre negative
moment (MC-)
UOW3
85
32.6
104
40
UOW4
110
42.2
138
52
Rail seat positive
moment (MR+)
UOW5
350
57.8
575
95
UOW6
350
57.8
580
96
Rail seat negative UOW7
moment (MR-)
UOW8
150
24.8
420
69
150
24.8
350
58
Design
moment
capacity
(kN.m)
38
40
95
58
RESULTS – IMPACT TESTING
Hard Track Support Condition
Experimental setup
High-speed camera for recording short
duration impact event
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RESULTS – IMPACT TESTING
Hard Track Support Condition
High-speed camera recording
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RESULTS – IMPACT TESTING
Hard Track Support Condition
Impact testing program (based on predicted
impact load from spectral analysis of WILD data)
Loading
duration
(msec)
14
15
13
14
5
915
580
14
6
915
590
14
7
915
637
13
8
915
613
13
9
2121
Maximu
m load
(kN)
606
570
615
625
915
630
13
10
915
630
14
11
1025
700
13
Observed
damage
no damage
no damage
no damage
first minor
crack
crack
propagation
no additional
damage
no additional
damage
no additional
damage
no additional
damage
no additional
damage
no additional
damage
550
500
Impact load (kN)
1
2
3
4
Drop
height
(mm)
910
910
915
915
600
450
400
350
300
250
200
150
100
50
0
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.1
Time (sec)
Sleeper deformation from image
processing
25
Sleeper vertical displacement (mm)
Test
No
650
20
15
10
5
0
Residual displacement
due to ballast crushing
-5
-10
-15
0
0.05
0.1
0.15
0.2
0.25
Time (sec)
0.3
0.35
0.4
0.45
RESULTS – IMPACT TESTING
Hard Track Support Condition
Cracking at rail seat
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22
Ballast crushing due to high
impact loads
RESULTS – LEVEL OF PRESTRESS
Dynamic relaxation tests
500
Initial state - wire intact
0
Prestressing Tendon 1
Prestressing Tendon 2
-500
-1000
Strain (strain)
-1500
-2000
-2500
-3000
-3500
-4000
Sleepers with damaged end and
exposed steel wires
Inertial effects
-4500
-5000
Final relaxed state
-5500
-6000
500
Initial state - wire intact
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
Prestressing Tendon 1
Prestressing Tendon 2
0
Time (sec)
-500
Level of prestress for undamaged sleeper is
Strain (strain)
-1000
-1500
Final relaxed state
-2000
-2500
-3000
Level of prestress for damaged sleeper is
Inertial effects
-3500
-4000
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0
0.5
1
1.5
2
2.5
Time (sec)
3
3.5
4
4.5
5
Concrete Strength and Modulus
of Elasticity
Cement Content and W/C Ratio
Ultrasonic Pulse Velocity
Concrete Carbonation
Chloride Content Analysis and
more
Concrete Strength
Ultrasonic Pulse Velocity
Carbonation testing
Level of Chloride at strand depth
Alkali Silica
Reaction
Delayed Ettringite
Formation/Sulphate Attack
Future Research Objectives:
 To revise current acceptance standards for
prestressed concrete sleepers based on results of
impact testing for fatigue and ultimate limit state
conditions.
 To revise current sleeper loading prediction
methodology to reflect findings from the
measurement and analysis of in-track data.
 To develop a sleeper acceptance framework for
sleepers.
 To establish a methodology for capacity rating of
concrete sleepers.
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