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1 Remaining Life of Concrete Sleepers: A Multifaceted Approach A/Prof Alex Remennikov School of Civil, Mining and Environmental Engineering University of Wollongong, NSW, Australia University of Wollongong

Remaining Life of Concrete Sleepers: A Multifaceted Approach

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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. Introduction. - PowerPoint PPT Presentation

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Remaining Life of Concrete Sleepers: A

Multifaceted Approach

A/Prof Alex RemennikovSchool of Civil, Mining and Environmental

EngineeringUniversity of Wollongong, NSW, Australia

University of Wollongong

Introduction

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This project will give track owners methods of more 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.

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Three-Pronged Characterisation Approach

Strength

Loading

Materials

• 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

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Loading Characterisation for Railway TrackCollection 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

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Static loads (extracted from WID data)

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Impact loads (extracted from WID data)

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𝒇= 𝑪.𝑫. 𝜶𝜷𝜶(𝒙− 𝜹)𝜶−𝟏𝒆−((𝒙−𝜹)𝜷 )𝜶

Impact load curve fitting

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1:10

1:100

1:1000

Impact load, forecasting

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Return period (years) 1 10 50 100 2000 Maximum likely incremental impact force (kN)

320 370 385 415 475

Strength Characterisation for Concrete Sleepers

Static bending testing

Dynamic impact testing

Fatigue testing

Prestressing tests

STATIC TESTS

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Rail seat vertical load tests – Negative and Positive Bending Moments

Centre Negative and Positive Bending Moment Tests

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DYNAMIC TESTING

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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

kNMonitoring equipment:• Dynamic load cell• Laser displacement

sensors• Accelerometers• Strain gauges• High-speed camera

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DYNAMIC TESTING

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Impact tests setup

Falling anvil 600 kg

Shock absorbers

Strong floor

Tested concrete sleepers

Sleeper support system

Optical trigger

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DYNAMIC TESTING

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Impact tests setup – sleepers support systems for different track moduli

Moderate track modulus (20-70 MPa)

Very soft track (8 MPa) Very hard track (120 MPa)

Ballast (200 mm)

Sand-rubber Mix (200 mm)

Strong Concrete Floor (1.5 m deep)

Strong Concrete Floor (1.5 m deep)

Ballast (150 mm)

Shock mat (10mm) Shock mat

(10mm)

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VERIFICATION OF PRESTRESSING

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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

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TYPICAL RESULTS – STATIC TESTING

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Rail Seat Bending Strength

Displacement (mm)

To

tal l

oad (

kN)

0 4 8 12 16 200

100

200

300

400

500

600UOW5UOW6

Displacement (mm)

To

tal l

oad (

kN)

0 4 8 12 16 200

100

200

300

400

500UOW7UOW8

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TYPICAL RESULTS – STATIC TESTING

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Centre Bending Strength

Displacement (mm)

Tota

l load (

kN)

0 10 20 30 400

20

40

60

80

100

120UOW1UOW2

Displacement (mm)

Tota

l load (

kN)

0 10 20 30 40 500

30

60

90

120

150UOW3UOW4

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TYPICAL SUMMARY OF STATIC TEST RESULTS

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Type of test Sleeper marks

Cracking load (kN)

Cracking moment (kN.m)

Ultimate load capacity (kN)

Ultimate moment capacity(kN.m)

Design moment capacity (kN.m)

1 Centre positive moment (MC+)

UOW1 78 30.0 99 3838

UOW2 85 32.6 99 38

2 Centre negative moment (MC-)

UOW3 85 32.6 104 4040

UOW4 110 42.2 138 52

3 Rail seat positive moment (MR+)

UOW5 350 57.8 575 9595

UOW6 350 57.8 580 96

4 Rail seat negative moment (MR-)

UOW7 150 24.8 420 6958

UOW8 150 24.8 350 58

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RESULTS – IMPACT TESTING

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Hard Track Support Condition

Experimental setup

High-speed camera for recording short duration impact event

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RESULTS – IMPACT TESTING

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Hard Track Support Condition

High-speed camera recording

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RESULTS – IMPACT TESTING

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Hard Track Support Condition

Impact testing program (based on predicted impact load from spectral analysis of WILD data)

Test No

Drop height (mm)

Maximum load (kN)

Loading duration (msec)

Observed damage

1 910 606 14 no damage2 910 570 15 no damage3 915 615 13 no damage4 915 625 14 first minor

crack

5 915 580 14 crack propagation

6 915 590 14 no additional damage

7 915 637 13 no additional damage

8 915 613 13 no additional damage

9 915 630 13 no additional damage

10 915 630 14 no additional damage

11 1025 700 13 no additional damage

Time (sec)

Imp

ac

t lo

ad

(k

N)

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10

50

100

150

200

250

300

350

400

450

500

550

600

650

Time (sec)

Sle

eper

ver

tica

l dis

pla

cem

ent

(mm

)

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45-15

-10

-5

0

5

10

15

20

25

Residual displacementdue to ballast crushing

Sleeper deformation from image processing

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RESULTS – IMPACT TESTING

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Hard Track Support Condition

Cracking at rail seat

Ballast crushing due to high impact loads

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RESULTS – LEVEL OF PRESTRESS

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Dynamic relaxation tests

Level of prestress for undamaged sleeper is

Time (sec)

Str

ain

(s

tra

in)

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-6000

-5500

-5000

-4500

-4000

-3500

-3000

-2500

-2000

-1500

-1000

-500

0

500

Initial state - wire intact

Final relaxed state

Inertial effects

Prestressing Tendon 1Prestressing Tendon 2

Sleepers with damaged end and exposed steel wires

Time (sec)

Str

ain

(str

ain

)

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-4000

-3500

-3000

-2500

-2000

-1500

-1000

-500

0

500

Initial state - wire intact

Final relaxed state

Inertial effects

Prestressing Tendon 1Prestressing Tendon 2

Level of prestress for damaged sleeper is

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Material Characterisation for Concrete Sleepers

Concrete Strength and Modulus of Elasticity

Cement Content and W/C Ratio

Concrete Carbonation

Chloride Content Analysis and more

Material Characterisation for Concrete Sleepers

Concrete Strength

Ultrasonic Pulse Velocity Carbonation testing

Material Characterisation for Concrete SleepersLevel of Chloride at strand depth

Alkali Silica Reaction

Delayed Ettringite Formation/Sulphate Attack

Future Research Objectives:

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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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