RAIL CRC

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A/Prof Alex Remennikov

University of Wollongong, NSW

Australia

International Concrete Crosstie & Fastening System Symposium

Research on Railway Sleepers Down Under

RailTEC, University of Illinois at Urbana-Champaign

RAIL CRC

Introduction

Country Rail Network – ARTC / JHR

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Cooperative Research Centre

CRC for Rail InnovationP

hase I

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

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

>$100M Funding & 5 R&D Themes

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Cooperative Research Centre

Economics, social, & environment

Operations & safety

Education & Training

Engineering & safety

Commercialisation & utilisation

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Ballast - FoulingEffect of Ballast Fouling

subgrade pumpingcoal

high ballast abrasion

field investigation at Bellambi

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Ballast – Impact load

Effect of Impact loads on ballast degradation ballast breakage

impact load

track stability

ballast breakage

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Ballast – Impact load

Effect of Impact loads on ballast degradation ballast breakage

impact load

track stability

ballast breakage

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Ballast - NDTNDT for Ballast Quality

ballast breakagetrack resilience

fine particle contamination

ballast layer

subballastformation

rail

sleeper

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Ballast - NDT

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Rail SquatsRail Squat Strategies

field investigation

UQ/Monash/CQU finite element analysismetallurgical studies

damage of components

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Short Pitch Irregularities

CQU

dipped welds

Detection of Short Pitch Irregularitiesvibration based detection

using AK Car axle box dataintegration algorithm

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Turnouts & CrossingReduction of Impact due to crossing and turnouts

Field Trials Sleeper/bearer padsComposite bearers

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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

I ntroduction RAIL CRC 13

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

IS THE CURRENT DESIGN OF CONCRETE SLEEPERS WRONG?

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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.

IS THE CURRENT DESIGN OF CONCRETE SLEEPERS WRONG?

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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.

IS THE CURRENT DESIGN OF CONCRETE SLEEPERS WRONG?

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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.

IS THE CURRENT DESIGN OF CONCRETE SLEEPERS WRONG?

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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.

IS THE CURRENT DESIGN OF CONCRETE SLEEPERS WRONG?

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Limit States Design Framework for Prestressed Concrete Sleepers

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RAIL CRC L imit states design

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 .

LIMIT STATES CONCEPT

× 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).

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RAIL CRC L imit states design

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.

PROPOSED LIMIT STATES OF PC SLEEPERS

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.

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.

ULTIMATE

FATIGUE

SERVICE-ABILITY

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DEFINITION OF A “FAILED” SLEEPER

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

Australian railway organisations would condemn a sleeper when its ability to hold

top of line or gauge is lost.

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.

L imit states design22

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Limit States Design and In-track Loads

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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.

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Data Analysis

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

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Data AnalysisImpact Force VS No of Axles (Combined Full & Empty Wagons)

2005-2006

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Impact Force on Each Wheel on Axle (kN)

Nu

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Allowable Impact Force(Code of Practice)

Straight line meansforecast of impacts isreliable beyond the12 months of data

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Other Factors Affecting In-Track Loads

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Experimental Investigation of Dynamic Ultimate Capacities of

Prestressed Concrete Sleepers for Limit States Design

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T esting RAIL CRC

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

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DYNAMIC TEST SETUP

Railseat sectionOverall view

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DYNAMIC TEST SETUP (VIDEO)

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DYNAMIC TEST SETUP (VIDEO)

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Impact forces between 500kN and 1600kN

IMPACT RESISTANCE OF SLEEPERS

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Impact failure of low profile sleeper at 1400kN

IMPACT RESISTANCE OF SLEEPERS

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Crack development under repeated loads

IMPACT RESISTANCE OF SLEEPERS

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Proposed Ultimate Limit State Design Equations:

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;

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(based on Murray and Bian (2011))

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Experimental Determination of Impact Load – Railseat Moment Relationship

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Numerical Determination of Impact Load – Railseat Moment Relationship

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Case Study: Evaluate the Capacity of the Existing Concrete Sleepers to Carry

Double Traffic Volume over next 10 years

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Analysis based on working stress method

Analysis based on ultimate limit state method

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C onclusions RAIL CRC

CONCLUSIONS

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.

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.

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Q &A

Thank you for your attention

Questions

& Answers