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Research project ______________________________________________
Faculty of Engineering - Civil and Environmental Engineering Dept.
______________________________________________
CIVE 531 Railway Engineering
𝑫𝒓. 𝒀𝒐𝒖𝒔𝒔𝒆𝒇 𝑨𝒕𝒕𝒂𝒍𝒍𝒂𝒉[𝟏]
2017
Railway Tracks Types, components and functions, materials, design (stresses)
By 𝑴𝒐𝒉𝒂𝒎𝒎𝒂𝒅 𝑺𝒂𝒆𝒆𝒅 𝑲𝒉𝒂𝒘𝒘𝒂𝒎 ∗[𝟐] ___________________________________________________
Abstract: This research project is highlighting on the railway tracks. there is a background
about tracks, talking about Types, components and functions, materials as basic construction, the
substructure Ballast, Sleepers and their different type, rails and rail welding, gauge, modern
Track forms, Track, Structures, Gauging - Curves – Cant - Turnouts - Crossings and also we
talking about in detailing of design for stresses.
Key words: modern Track forms, railway tracks, Structures, design
_______________________________________________________________ _________________ [1] Prof. Dr. Youssef Tewfik Youssef Attallah, Civil Engineering Department, Faculty of Engineering, Beirut Arab
University, Beirut, Lebanon Tel. (Mob.): 70 18 63 20, e-mail: [email protected], [email protected]
[2] * Research project author: Student Mohammad Saeed Anwar Khawwam. Civil Engineering Department,
Faculty of Engineering, Beirut Arab University, Beirut, Lebanon Tel. (Mob.): 78 99 05 44, e-mail:
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TABLE OF CONTENTS
Title page................................................................................................................ X
Abstract................................................................................................................... X
TABLE OF CONTENTS ……………………………………………………………....…. 2 NOMENCLATURE ................................................................................................... 3
General background………………………………………………………...........4 INTRODUCTION ……………………………………………………………….……....….4
Infrastructure…..…………………………………………………………….....….4 Basic Construction…………………………………………………………..……5 The Sub-Structure……………………………………………………………...….5 Ballast…………………………………………………………………………..……6 Track……………………………………………………………………………...….6 Sleepers………………………………………………………………….….………6 Rail………………………………………………………………………………..….7 Rail Welding……………………………………………………………………..…8 Gauge………………………………………………………………………….…....8 Modern Track Forms………………………………………………………….….8 Gauging……………………………………………………………………….....…9 Curves………………………………………………………………………...…....9 Cant…………………………………………………………………………………10 Turnouts……………………………………………………………………………10 Crossings…………………………………………………………………….…....10 Railway Track Structural Design………………………………………………10 Deflection profile……………………………………………………………...….11 Master diagram……………………………………………………………….......12 Load Deflection and bending Moment………………………………………..12 Design Steps………………………………………………………………………13 Stresses in Rail Base……………………………………………………….……13 Stresses in Rail Head……………………………………………………….……13 Contact Stresses…………………………………………………………...……..13 Conclusion…………………………………………………………………………14 REFERENCES……………………………………………………………….…….14
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NOMENCLATURE
A Section area S subgrade factor Z section modulus μ coefficient of adjacent axles D Wheel diameter r1 Wheel radius r2 rail radius FOS factor of safety D Wheel diameter E Elasticity modulus 𝒓𝟎 Track Resistance Expansion zone Length change L’ balanded zone h Track cant V speed σ stress z Deflection of beam Y Lateral load
Units m meters in inch ft. feet kg kilogram t. ton (Wight) lb. pound (weight)
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1.0 General background
Railways have taken major part in transporting population, resources, merchandises, etc. over the large contingent of any country. Railway industry has significantly grown in the past century and has continuingly developed new suitable technology for its solution to specific requirements. In many countries, the traditional railway system is the ballasted track, which consists of rails, rail pads, and concrete sleepers (ties) laid on ballast and subgrade. Recently, the demand of track usages has greatly increased. The increase in frequency of traffic for passenger trains and the rise in loads of freight trains over recent years have also been a significant factor contributing to the deterioration of the railway track system. The increase in transport capacity has been stimulated by the growing industrial need for long-distance freight conveyancing, especially in large countries
2.0 Introduction
Track is the base upon which the railway runs. To give a train a good ride, the track alignment
must be set to within a millimetre of the design. Track design and construction is part of a
complex and multidisciplinary engineering science involving earthworks, steelwork, timber and
suspension systems – the infrastructure of the railway. Many different systems exist throughout
the world and there are many variations in their performance and maintenance. This page looks
at the basics of infrastructure and track design and construction with drawings, photos and
examples from around the world.
3.0 Infrastructure
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3.1 Basic Construction
Track is the most obvious part of a railway route but there is a sub-structure supporting the track
which is equally as important in ensuring a safe and comfortable ride for the train and its
passengers or freight. The infrastructure diagram here shows the principal parts of an electrified,
double-track line. The total width across the two-track alignment will be about 15 m (50 ft.) for a
modern formation. The "cess" shown each side of the alignment is the area available for a
walkway or refuge for staff working on the track
.
3.2 The Sub-Structure
This part of the road consists of three main elements; the formation, the sub-ballast and the
ballast. The formation is the ground upon which the track will be laid. It can be the natural
ground level or "grade" or it can be an embankment or cutting. It is important that the formation
is made of the right materials and is properly compacted to carry the loads of passing trains. The
formation under the track has a "camber" rather like that seen on a roadway. This is to ensure
ease of water run-off to the drains provided on each side of the line. The track itself is supported
on "ballast", made up of stones - usually granite or, in the US, basalt - below which is a layer of
sand, which separates it from the formation. For new or renewed formations, the sand is
normally laid over some sort of geotechnical screen or mesh to separate it from the foundation
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material below and beyond them, there is a walkway area. This may just be a cleared path for
staff to walk safely, avoiding passing trains or, on modernised routes, a properly constructed
path. Next to this path will be a cable trough. These were originally concrete but are nowadays
often made of plastic. Cables crossing the track are protected by a plastic tube, usually bright
orange. Proper cable protection is essential to prevent damage by animals, track maintenance
tools, weather and fire. Many countries around the world don't fence their railways, assuming
people will treat them like roads and look both ways before crossing.
3.3 Ballast
Ballast is provided to give support, load transfer and drainage to the track and t hereby keep
water away from the rails and sleepers. Ballast must support the weight of the track and the
considerable cyclic loading of passing trains. Individual loads on rails can be as high as 50
tonnes and around 80 short tons on a heavy haul freight line. Ballast is made up of stones of
granite or a similar material and should be rough in shape to improve the locking of stones.
Ballast will be laid to a depth of 9 to 12 inches (up to 300 mm on a high speed track). Ballast
weighs about 1,600 to 1,800 kg/cu/m
3.4 Track
The usual track form consists of the two steel rails, secured on sleepers (or crossties, shortened to
ties,) so as to keep the rails at the correct distance apart (the gauge) and capable of supporting the
weight of trains. There are various types of sleepers and methods of securing the rails to
them. Sleepers are normally spaced at 650 mm (25 ins) to 760 mm (30 ins) intervals, depending
on the particular railway's standard requirements.
3.5 Sleepers
The sleepers must ensure the following:
appropriate load transfers and distribution from the rails to the ballast
constant rail spacing, as specified by the track gauge
mounting of the rails on the sleepers at an inclination of 1/20 or 1/40
adequate mechanical strength both in the vertical and in the horizontal direction
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3.6 Rail
The standard form of rail used around the world is the "flat
bottom" rail. It has a wide base or "foot" and narrower top
or "head". This was known as "Bullhead" rail and is shown
in comparison with the standard type in the diagram left.
Bullhead rail was originally designed with reuse in mind. It
was intended that it would be turned over when the top had
worn but this proved impossible because the underside also wore where it had been secured to
the sleeper. Bullhead rail has to be mounted in a special "chair" made of cast iron and secured
by a "key" wedged between the rail web and the chair. The chairs are secured to the sleepers by
"coach screws". The arrangement can be seen in the first photo below: The photo above shows a
flat bottom rail clipped to a baseplate under the rail. Flat bottom rails can also be "spiked"
directly to the sleepers.
Rail divided by three part: - rail head: the top surface that contacts the wheel tire - rail web: the middle part that supports the rail head, like columns - rail foot: the bottom part that distributes the load from the web to the underlying superstructure components.
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3.7 Rail Welding
Modern track work uses long welded rail lengths to provide a better ride, reduce wear, reduce
damage to trains and eliminate the noise associated with rail joints. Rail welding is a complex
art (or science) depending on how you feel about it. There are two main types of welding used
for rails: Thermite welding and Flash Butt welding.
Continuous welded rail with free-end
N t
cmkgrr
tAE
r
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oo
t /52
)(0
22
3.8 Gauge
The standard track gauge - the distance between the
two rails - is 4 ft. 8½ in or 1435 mm. but many other
gauges, wider and narrower than this, are in use
around the world. Gauge is often intentionally widened slightly on curved track.
4.0 Modern Track Forms
There are now a range of modern track forms using a concrete base. They are generally used in
special locations such as tunnels or bridges where a rigid base is required to ensure track stability
in relation to the surrounding structures. This type of track, usually called "slab track" or "non-
ballasted" track The earth mat is a steel mesh screen provided on electrified railways to try to
keep stray return currents from connecting to utilities pipes and nearby steel
structures. Earthling must be strictly controlled otherwise serious and expensive problems will
occur, made more serious and expensive because they involve other people's property. Some slab
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track systems have the sleepers resting on rubber or similar pads so that they become "floating
slab track". Floating track is used as a way of reducing vibration. Hong Kong Mass Transit
Railway is fond of it, since its lines run through very densely populated areas.
5.0 Gauging
The line of route has to be checked from time to time to ensure that the structures are not
interfering with the gauge. A line is always gauged when a new type of rolling stock is to be
introduced. It is important to see that the small variations in track position, platform edge, cable
duct location and signal equipment hasn't been allowed to creep inwards during maintenance and
renewal programmes. Gauging used to be done by hand locally (and still is from time to time in
special circumstances) but nowadays, it is mostly done with a special train. The train used
consist of a special car with a wooden frame built almost to the gauge limits. The edges of the
frame were fitted with lead fingers so that, if they hit anything as the train moved along, they
would bend to indicate the location and depth of intrusion. Modern gauging trains are fitted with
optical or laser equipment. The optical system uses lights to spread beams of light out from the
train as it runs along the line. Suitably mounted cameras record the breaks in the light beams to
provide the gauging information. The train can run at up to 50 mi/h (80 km/h) but, of course, the
runs have to be done at night. Laser beams are also used but, as they rotate round the train and
form a "spiral" of light, the method suffers from gaps which can allow intrusions to be missed.
6.0 Curves
Curves in the track are almost a science on their own. Careful calculations are required to ensure
that curves are designed and maintained properly and that train speeds are allowed to reach a
reasonable level without causing too much lateral stress on the track or inducing a
derailment. There are both vertical curves and horizontal curves. There is also a section of
track on either side of a curve known as the transition, where the track is changing from straight
to a curve or from a curve of one radius to one of another radius.
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7.0 Cant
Cant is the name used to describe the cross level
angle of track on a curve, which is used to
compensate for lateral forces generated by the
train as it passes through the curve. In effect, the
sleepers are laid at an angle so that the outer rail
on the curve is at a higher level than the inner
rail. In the US, it is known as super elevation.
Cant is measured either in degrees or in linear
dimensions. On standard gauge track (1435 mm
or 4ft. 8½ins.) 150 mm or 6 ins. of cant is equal to
6 degrees. This is the normal maximum in the
UK. The maximum amount of cant deficiency
allowed is 110 mm (4½ ins.).
8.0 Turnouts
I have used the word "turnout" to describe the junctions in track work where lines diverge or
converge so as to avoid "points" (UK) or "switches" (US), both of which terms can be
confusing. In the railway "trade", turnouts are referred to as "switch and crossing work". A
turnout consists of a number of parts as follows: The moving part of the turnout is the switch
"blade" or "point", one for each route. The two blades are fixed to each other by a tie bar to
ensure that when one is against its stock rail, the other is fully clear and will provide room for the
wheel flange to pass through cleanly. Either side of the crossing area, wing and check rails are
provided to assist the guidance of the wheelsets through the crossing.
9.0 Crossings
The crossing can be cast or fabricated. Rails are usually made of steel with a large iron content
but a little manganese is added to crossings and some heavily used rails to increase resistance to
wear. Below is a photo of an example of a cast manganese crossing. A crossing is also
sometimes referred to as a "frog
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___________________________________________________________________________
10.0 Railway Track Structural Design
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Design Steps (AREMA, U.S. DoD, and Others)
(Generalized)
1. Select design wheel load based on most common, heaviest car and desired
track speed. Consider all wheels in a truck and proximity of adjacent cars.
2. Select a Track Modulus, u or k, based on desired design deflection
3. Select rail size and section
4. Determine moment and loading coefficients
5. Check rail bending stress
6. Choose trial tie spacing and calculate maximum rail seat load
7. Select tie size
8. Check tie bending stress
9. Determine and select plate size based on minimum area
10. Determine ballast surface stress
11. Determine ballast depth based on allowable subgrade stress
12. Calculate track deflection under load and check on acceptability
13. If deflection is unacceptable, re-do design
Always consider economics!
Stresses in Rail Base
2maxBase t/cm S)3(1
Z4
LQ σ
Stresses in Rail Head
2
5-
Suitable r 10 5.26 Q
FOS
Failure
Contact Stresses
3max
2
21
11178 Q
rrC
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Conclusion
As a conclusion, we see from a general view to the world that railway has many advantages if we
compare it with the other transportations such as economic, environmental, and more safe. And
these are completed by the development of the railway domain like higher speed of the train,
introducing new tools and techniques and approaches and we are waiting for new discovery. And
we see same formula to calculate a stresses to design
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speed railway” ieee transactions on intelligent transportation systems,2014.
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