Railroading Down Under - RailTEC - University of Illinois at Urbana

Report
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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
RAIL CRC
Introduction
Country Rail Network – ARTC / JHR
RAIL CRC
Phase II: 2007-2013
Cooperative Research Centre
CRC for Rail Innovation
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
Commercialisation
& utilisation
Engineering &
safety
Economics, social,
& environment
Operations &
safety
Education &
Training
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Ballast - Fouling
Effect of Ballast Fouling
subgrade pumping
coal
high ballast abrasion
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field investigation at Bellambi
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Ballast – Impact load
Effect of Impact loads on ballast degradation
ballast breakage
impact load
track stability
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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 - NDT
NDT for Ballast Quality
ballast breakage 
track resilience 
fine particle contamination 
rail
sleeper
ballast layer
subballast
formation
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Ballast - NDT
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Rail Squats
UQ/Monash/CQU
Rail Squat Strategies
field investigation 
finite element analysis 
metallurgical studies 
damage of components
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Short Pitch Irregularities
CQU
Detection of Short Pitch Irregularities
vibration based detection 
using AK Car axle box data 
integration algorithm 
dipped welds
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Turnouts & Crossing
Reduction of Impact due to crossing and turnouts
Field Trials
Sleeper/bearer pads
Composite 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
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I ntroduction
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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. AS1085.142009, AREMA Manual for Railway
Engineering (2010).
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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.
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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.
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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.
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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.
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Limit States Design Framework for
Prestressed Concrete Sleepers
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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).
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L imit states design
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PROPOSED LIMIT STATES OF PC
SLEEPERS
ULTIMATE
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.
FATIGUE
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.
SERVICEABILITY
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.
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L imit states design
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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.
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L imit states design
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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
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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<50
50-60
60-70
70-80
80-90
90-100
100-110
110-120
120-130
130-140
140-150
150-160
160-170
170-180
180-190
190-200
200-210
210-220
220-230
230-240
240-250
250-260
260-270
270-280
280-290
290-300
300-310
310-320
320-330
330-340
340-350
350-360
360-370
370-380
380-390
390-400
400-410
410-420
420-430
430-440
440-450
450-460
460-470
470-480
480-490
490-500
500-510
510-520
520-530
530-540
540-550
Number of Axles
Data Analysis
Impact Force VS No of Axles (Combined Full & Empty Wagons)
2005-2006
10000000
1000000
10000
1000
100
Allowable Impact Force
(Code of Practice)
100000
Straight line means
forecast of impacts is
reliable beyond the
12 months of data
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Impact Force on Each Wheel on Axle (kN)
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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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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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T esting
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DYNAMIC TEST SETUP
Overall view
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T esting
Railseat section
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DYNAMIC TEST SETUP (VIDEO)
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DYNAMIC TEST SETUP (VIDEO)
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IMPACT RESISTANCE OF SLEEPERS
Impact forces between 500kN and 1600kN
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IMPACT RESISTANCE OF SLEEPERS
Impact failure of low profile sleeper at 1400kN
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IMPACT RESISTANCE OF SLEEPERS
Crack development under repeated loads
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T esting
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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;
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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
Analysis based on working stress method
Analysis based on ultimate limit state method
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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.
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C onclusions
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Thank you for your attention
Questions
& Answers
Q &A
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