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Research on Railway Sleepers Down Under. International Concrete Crosstie & Fastening System Symposium. RailTEC , University of Illinois at Urbana-Champaign. A/Prof Alex Remennikov. University of Wollongong, NSW Australia. Introduction. Country Rail Network – ARTC / JHR.

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slide1

Research on Railway Sleepers Down Under

International Concrete Crosstie & Fastening System Symposium

RailTEC, University of Illinois at Urbana-Champaign

A/Prof Alex Remennikov

University of Wollongong, NSW

Australia

introduction
Introduction

Country Rail Network – ARTC / JHR

cooperative research centre
Cooperative Research Centre

CRC for Rail Innovation

Core Industry Partners: Ralcorp, QR, ARA, ARTC, and Rio Tinto Iron Ore.

Phase II: 2007-2013

Universities: UoW, Monash, CQU, UQ, QUT, and UniSA

>$100M Funding & 5 R&D Themes

cooperative research centre1
Cooperative Research Centre

Economics, social, & environment

Commercialisation & utilisation

Operations & safety

Engineering & safety

Education & Training

4

ballast fouling
Ballast - Fouling

Effect of Ballast Fouling

subgrade pumping

coal

high ballast abrasion

field investigation at Bellambi

5

ballast impact load
Ballast – Impact load

Effect of Impact loads on ballast degradation

ballast breakage

impact load

track stability

ballast breakage

6

ballast impact load1
Ballast – Impact load

Effect of Impact loads on ballast degradation

ballast breakage

impact load

track stability

ballast breakage

7

ballast ndt
Ballast - NDT

NDT for Ballast Quality

ballast breakage

track resilience

fine particle contamination

rail

sleeper

ballast layer

subballast

formation

rail squats
Rail Squats

Rail Squat Strategies

field investigation

UQ/Monash/CQU

finite element analysis

metallurgical studies

damage of components

short pitch irregularities
Short Pitch Irregularities

Detection of Short Pitch Irregularities

CQU

vibration based detection

using AK Car axle box data

integration algorithm

dipped welds

turnouts crossing
Turnouts & Crossing

Reduction of Impact due to crossing and turnouts

Field Trials

Sleeper/bearer pads

Composite bearers

concrete sleepers projects
Concrete Sleepers Projects

Innovative/Automated Track Maintenance and Upgrading Technologies

Dynamic analysis of track and the assessment of its capacity with particular reference to concrete sleepers

Key Industry Partners

13

I ntroduction

RAIL CRC

slide14

IS THE CURRENT DESIGN OF CONCRETE SLEEPERS WRONG?

  • Concrete sleepers are designed according to a 19th century deterministic method called ‘permissible stress design’ (e.g. AS1085.14-2009, AREMA Manual for RailwayEngineering (2010).

14

I ntroduction

RAIL CRC

slide15

IS THE CURRENT DESIGN OF CONCRETE SLEEPERS WRONG?

  • Today almost all structural codes around the world use limit states design (aka Load and Resistance Factor Design LRFD), except for codes used in the design of concrete railway sleepers.

15

I ntroduction

RAIL CRC

slide16

IS THE CURRENT DESIGN OF CONCRETE SLEEPERS WRONG?

  • There is a widespread perception in the railway industry that concrete sleepers have unused reserves of strength.
  • E.g., sleepers are generally replaced only because of non-design factors such as serious damage due to train derailment or inappropriate materials in the concrete mix or manufacturing faults.

16

I ntroduction

RAIL CRC

slide17

IS THE CURRENT DESIGN OF CONCRETE SLEEPERS WRONG?

  • If concrete sleepers have unused reserve strength, increases in axle loads & train speeds may not, for example, need sleepers to be replaced with heavier ones.
  • The saving in expenditure around AU$100,000 per km of track could be achieved if the 22t sleepers in that section of track are found to not need replacing with higher rated sleepers.

17

I ntroduction

RAIL CRC

slide18

IS THE CURRENT DESIGN OF CONCRETE SLEEPERS WRONG?

  • The current design approach is not wrong, but there is clearly a need for a method of designing and rating of concrete sleepers that is more rational than permissible stress design and which allows for the inherent variability of strength and of applied loads.
  • Development of the framework for designing concrete sleepers using limit states approach is discussed in this presentation.

18

I ntroduction

RAIL CRC

slide20

LIMIT STATES CONCEPT

Limit state deems that the strength of a structure is satisfactory if its calculated nominal capacity, reduced by a capacity factor , exceeds the sum of the nominal load effects multiplied by load factors .

×Nominal load effects ≤ ×Nominal capacity

where the nominal load effects (e.g. bending moments) are determined from the nominal applied loads by an appropriate method of structural analysis (static or dynamic).

20

L imit states design

RAIL CRC

slide21

PROPOSEDLIMIT STATES OF PC SLEEPERS

A single once-off event such a severe wheel flat that generates an impulsive load capable of failing a single concrete sleeper. Failure under such a severe event would fit within failure definitions causing severe cracking at the rail seat or at the midspan.

ULTIMATE

A time-dependent limit state where a single concrete sleeper accumulates damage progressively over a period of years to a point where it is considered to have reached failure. Such failure could come about from excessive accumulated abrasion or from cracking having grown progressively more severe under repeated loading impact forces over its lifetime.

FATIGUE

This limit state defines a condition where sleeper failure is beginning to impose some restrictions on the operational capacity of the track. The failure of a single sleeper is rarely a cause of a speed restriction or a line closure. However, when there is a failure of a cluster of sleepers, an operational restriction is usually applied until the problem is rectified.

SERVICE-ABILITY

21

L imit states design

RAIL CRC

slide22

DEFINITION OF A “FAILED” SLEEPER

Australian railway organisations would condemn a sleeper when its ability to hold top of line or gauge is lost.

abrasion at the bottom of the sleeper causing a loss of top;

abrasion at the rail seat causing a loss of top;

severe cracks at the rail seat causing the ‘anchor’ of the fastening system to move and spread the gauge;

severe cracks at the midspan of the sleeper causing the sleeper to ‘flex’ and spread the gauge;

Only severe cracking leading to sleeper’s inability to hold top of line and gauge are considered as the failure conditions defining a limit state.

22

L imit states design

RAIL CRC

data collection
Data Collection
  • In limit states design the actual spectrum of forces is needed and in-field measurements are required.
  • 12 months of WILD wheel impact data has been gathered from QR sites at Braeside & Raglan in Central Queensland.
  • Approximately 5 million measurements of impacts means data is statistically robust.

24

RAIL CRC

data analysis
Data Analysis

Variability of wagon weight for the nominal 28t (2 x 137 kN) axle loads. Mean force is 128 kN, standard deviation 13 kN.

25

data analysis1
Data Analysis

Straight line means

forecast of impacts is

reliable beyond the

12 months of data

26

slide28

Experimental Investigation of Dynamic Ultimate Capacities of Prestressed Concrete Sleepers for Limit States Design

28

slide29

DYNAMIC TESTING PROCEDURE

Drop hammer impact testing machine

Frame height = 6m

Falling mass = 600 kg

Impact load up to 2000 kN

Impact velocity up to 10 m/s

Operation efficiency 98%

Working area = 5x2.5m

29

T esting

RAIL CRC

slide30

DYNAMIC TEST SETUP

Overall view

Railseat section

30

T esting

RAIL CRC

slide31

DYNAMIC TEST SETUP (VIDEO)

31

T esting

RAIL CRC

slide32

DYNAMIC TEST SETUP (VIDEO)

32

T esting

RAIL CRC

slide33

IMPACT RESISTANCE OF SLEEPERS

Impact forces between 500kN and 1600kN

33

T esting

RAIL CRC

slide34

IMPACT RESISTANCE OF SLEEPERS

Impact failure of low profile sleeper at 1400kN

34

T esting

RAIL CRC

slide35

IMPACT RESISTANCE OF SLEEPERS

Crack development under repeated loads

35

T esting

RAIL CRC

slide36

Proposed Ultimate Limit State Design Equations:

(based on Murray and Bian (2011))

where

MQ is the moment induced in the sleeper by the design value of the wagon weight force;

MI is the moment induced in the sleeper by the ultimate impact force I for the specified return period;

36

slide39

Case Study: Evaluate the Capacity of the Existing Concrete Sleepers to Carry Double Traffic Volume over next 10 years

Analysis based on working stress method

Analysis based on ultimate limit state method

39

slide40

CONCLUSIONS

Extensive investigations at UoW within the framework of the Rail-CRC have addressed the spectrum and magnitudes of dynamic forces, the reserve capacity of typical PC sleepers, and the development of a new limit states design concept.

The proposed methodology has been successfully applied to the problems involving increased traffic volume and increased axle loads where the untapped reserve capacity allowed to not replacing the existing concrete sleepers with higher rated sleepers.

40

C onclusions

RAIL CRC

slide41

Thank you for your attention

Questions

& Answers

Q&A

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