Sleepers in railway engineering

8/18/2019 Sleepers in railway engineering

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SLEEPERSRailways and Airport Engineering

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Sleepers

Sleepers are members generally laid

transverse to the rails on which the

rails are supported and fxed, to

transer the loads rom the rails to

the ballast and the subgrade below

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!unctions o Sleepers

"o hold the rails to correct gauge and alignment "o act as a elastic medium between the ballast and rails

"ranserring the load evenly rom rails to wider area o

ballast

"o support the rails in proper level in straight trac# and

in proper super elevation on curved trac#

Sleepers also add to the longitudinal and lateral

stability o the permanent trac#

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Re%uirements o Sleepers

Sleepers used should be economical & initial andmaintenance cost should be minimum

"he fttings o the sleepers should be such that they

can be easily ad'usted during maintenance operations (

easy liting, pac#ing, removal and replacement)

"he weight o the sleepers should not be too heavy or

excessively light

"he design o the sleepers should be such that the

gauge, alignment o trac# and levels o the rails can be

easily ad'usted and maintained

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Re%uirements o Sleepers

"he sleeper design and spacing should acilitate easyremoval and replacement o ballast

+t should resists shoc#s and vibration due to heavy load

o high speed trains

esign o sleepers are in such a way that they are not

damaged during pac#ing processes

An ideal sleeper should also have an anti & sabotage

and anti & thet %ualities

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.aying o Sleepers

Sleepers shall be laid s%uare to rails on straight and

radially on curve/

"he sleeper spacing should be mar#ed on outer rail in

case o curved trac#/

0loser spacing should be provided at 'oint sleepers o

fsh plated 'oints and between 'oint sleeper and

shoulder sleeper/


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S.EEER E3S+"4 A3 SA0+35 6!S.EEERS

Sleeper density is the number o sleepers perrail length/

+t is specifed as (7 8 x) or (3 8 x), where 7 or

3 is the length o the rail in metres and x is anumber that varies according to actors such as

(a) axle load and speed,

(b) type and section o rails,

(c) type and strength o the sleepers, (d) type o ballast and depth o ballast

cushion, and

(e) nature o ormation/

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+ the sleeper density is 78 on a broadgauge route and

the length o the rail is 1 m,

it implies that 1 8 : 2; sleepers will beused per rail length o the trac# on that route/

"he spacing o sleepers is fxed dependingupon the sleeper density/

Spacing is not #ept uniorm throughout therail length/ +t is closer near the 'oints becauseo the wea#ness o the 'oints and impact omoving loads on them

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0lassifcation o Sleepers

=ooden sleepers

7etal sleepers

0ast iron sleepers

Steel sleepers

0oncrete sleepers

Reinorced concrete sleepers

restressed concrete sleepers

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=ooden Sleepers

"hese sleepers are regarded to be the best asthey satisy all the re%uirements and suitableor trac# circuiting

"he lie o wooden sleepers depends upontheir ability to resist wear, attac# by whiteants and %uality o timber used

Standard si>e o wooden sleepers or di?erent

gauges @/5 & 2$;2*;1;mm

7/5 & 19;2;11$ mm

3/5/ & 1*2;1*;1;; mm

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=ooden Sleepers

Advantages

Easy to manuacture andhandling/

Suitable or trac# circuitedarea/

Bery ew ftting and simple indesign

Suitable or bridges,

ointsC0rossings/ Alignment can be easily

corrected/

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=ooden Sleepers

Disadvantages

.esser lie/

iDcult to maintain the gauge/

Susceptible to fre ha>ards/

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escription o =ooden Sleepers

Durable and non durable types of sleepers

.ie o Sleeper

urable1< years (@5) and 1 years (75)

3onurable

12 to 1- years/

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7etal Sleepers

ue to scarcity o wooden sleepers, high cost and short

lie, metal sleepers are now being adopted in +ndia

Re%uirements

Should bear the tensile and compressive stresses

"amping and pac#ing o ballast should not disturb

the sleeper

!or trac# circuiting, insulation should be possible

7etal sleepers should be overall economical as

compared to wooden sleepers

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Advantages o 7etal Sleepers

Fniorm in strength and durability

erormance o ftting are better and hence less creep

occurs

Economical & as long lie and easy maintenance

Ad'ustment and maintenance o gauge is easy

Scrap value is more

Resistance to fre ha>ards

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isadvantages o 7etal

Sleepers 7ore ballast are re%uired 7ore number o fttings are re%uired & diDcult to

maintain and inspect

.iable to rusting C corrosion

"rac# circuiting good conductor o electricity

Fnsuitable or bridges, level crossing and point and

crossing

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Steel sleepers are o two types

Gey type steel sleepers

.ugs or 'aws are pressed out o the plate

"wo holes are punched into either side o

the plate to accommodate specially deigned

H loose 'awsI/ Rails are held with the help o

two standard #eys driven into the loose 'aws

0lip and bolt type steel

sleepers +n this type o sleeper , clips and bolts are used

or holding the rails/ crac#s are not developedin the sleepers as the holes or the bolts aresmall and circular/ +t re%uires $ clips and $bolts or holding each rails/

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Steel Sleeper with pressed up

lug

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Steel Sleepers with loose 'aws

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Advantages of Steel Sleepers

.onger lie

@etter Stability

.esser damage during handling C"ransport

Easy to maintain 5auge Simple 7anuacturing rocess

Jigh Scrap value

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Disadvantages of Steel

Sleepers

.iable or corrosion

3ot ft or trac# circuited area

evelops crac#s at rail seat during

service

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Usual defects in Steel Sleepers

Rusted and corroded metal

0rac#s at rail seat or near the lugs

Elongation o holes

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0ast +ron Sleepers

ot or @owl Sleepers

late Sleepers

@ox Sleepers

0 S" & < sleepers (0ombination o plate and box type)

Rail ree duplex sleeper

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ot or bowl sleeper

ot sleeper consist o two bowlsplaced under each rail andconnected together by a tiebar/ "hetotal e?ective area o both the potsis ;/$-$ s%/ m/ Each pot is providedwith two holes or inspection and

pac#ing o ballast/ 6n the top o eachpot, a rail seat is provided to holdrails at an inward slope o 1 in 2;/

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late sleeperK

late sleepers consists o two rectangularplates o 9-$ mm L ;* mm in si>e withshort side parallel to rail/ "he plates are

provided with pro'ecting ribs in thebottom to provide a grip in the ballast orlateral stability/ "he plates are held inposition by tiebar/ Sti?ness are provided

at the top o the plate to increase thestrength/ +t provides the e?ective bearingarea o ;/$-$s%/ m per sleeper/

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@ox SleeperK

"hese sleepers are not in user thesedays/ @ox sleepers are similar toplate sleepers/ +n this type osleeper, a box is provided at the topo each plate to hold the rails/

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0S"< SleeperK

0S"< sleeper is more satisactorythan other 0/+/ Sleepers and isextensively used in +ndian Railwayssince last thirty years/ +t is acombination o pot, plate, and boxsleeper/


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uplex SleepersK

uplex sleepers are also #nown as railree duplex sleepers and have been usedat rail 'oints in con'unction with 0S"M<

sleepers/ "hese sleepers are used at rail 'oints to prevent cantilever actionbetween two supports o the 0S"<sleepers/ "hese consists o two plates,

each o si>e 9*; mm L *; mm/ "heplates are placed with the longer sideparallel to the rails and are connectedwith a tiebar/

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Advantage o cast iron sleepers

.ess corrosion

.ess probability o crac#ing at rail seat

Easy to manuacture

Jigher scrap value

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0ast +ron Sleepers

Disadvantages of Cast Iron Sleepers

3ot suitable or high speed route/

iDcult to maintain the 5auge/

.esser lateral stability/ 3ot ft or trac# circuited area/

3ot suitable or mechanical maintenance/

"ie bars wea#ened by corrosion/


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0oncrete Sleepers

Types of concrete Sleepers

restressed 0oncrete Sleepers

Reinorced concrete Sleepers

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0oncrete Sleepers

Advantages of concrete Sleepers

5reater stability

"rac# geometry maintained or much/ .onger duration

hence economical

@est suited or machine maintenance

Suitable or "rac# circuiting area

3o chances o damage by freC corrosion

3o possibility o thet

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0oncrete Sleepers

3o chances o gauge widening/

@est perormance on 5uard rails , .evel 0rossings,

0hec# rail in curve/

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0oncrete Sleepers

Disadvantage

Jandling and laying is diDcult being heavy/

amage is very heavy in case o derailment/

3o scrap value/

3ot suitable or manual pac#ing/

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0oncrete Sleepers

ue to the shortage o wooden sleepers and need or

better design and economy o sleepers on sustainable

basis, concrete sleepers are developed

0oncrete sleepers ound to be a ideal materials or

sleepers due to

7ade o strong and homogeneous material

+mpervious to the e?ect o moisture

Fna?ected by chemical attac# o atmospheric gases

or sub & soil salts

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0oncrete Sleepers

Special rail astenings are necessary or concrete

sleepers to achieve the ollowing

"o prevent deterioration o concrete at the rail seat

through continuous pounding action

"o contain the loc#ed up temperature stresses

A shoc# absorbing or a resilient plate pad is provided at

the rail seat to prevent deterioration and hard & riding

!lexible astening are re%uired to be used such as

elastic spi#es, clip or spring spi#e etc/,

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Reinorced 0oncrete Sleepers

"hrough type or one piece or mono bloc#

=hen sub'ected to tensile stresses, crac#s are

developed on the tension side

ue to repetition o load over the sleepers the crac#

get wider which results in ailure o sleepers

0omposite or @loc# and tie type

3ot sub'ect to same degree o tensile stress, since

inverted " & section is used as a tie member/ 3ot

used now a days

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re stressed 0oncrete

Sleepers 0oncrete is put under very high initial compression andthe design is based on

7ax/ permissible compressive strength o 211 #gCcm2

7inimum cube crushing strength o concrete in the

sleepers is $22 #gCcm2 at 29 days

"he pre & stressed wires are stressed to an initial

stress o 9/92 #gCcm2

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Sleepers in railway engineering