IS 456:2000

IS 456 : 2000 , The Holy Book For Indian Civil engineers

(Plain and Reinforced Concrete Code of Practice)

Contents:-

                                        Section 1 General

1) Scope

2) References

3) Terminology

4) Symbols

                         Section 2  Materials, workmanship, Inspection and Testing

5) Materials

6) Concrete

7) Workability of  concrete 

8) Durability of concrete

9) Concrete Mix Proportioning

10) Production Of Concrete

11) Formwork

12) Assembly Of Reinforcement 

13) Transporting, placing, compaction, and Curing

14) Concrete Under special Conditions

15) sampling and Strength of Designed concrete mix

16) Acceptance Criteria

17) Inspection an Testing of structure 

                Section 3 General Design Consideration

18) Bases for Design

19) Loads and Forces

20) Stability of the Structure 

21) Fire Resistance 

22) Analysis

23) Beams

24) Solid Slabs

25) Compression Members

26) Requirements Governing Reinforcement and Detailing

27) Expansion Joints

  Section 4 Special design Requirements For Structural Members And Systems

28) Concrete  Corbels

29) Deep Beams

30) Ribbed, Hollow Block or Voided Slab

31) Flat Slabs

32) Walls

33) Stairs

34) Footings

Section 5 Structural Design(limit state method)

35) Safety and Serviceability Requirements 

36) Characteristics And design Values and Partial Safety Factors

37) Analysis

38) Limit State of Collapse: Flexure

39) Limit State of Collapse Compression

40) Limit State of Collapse Shear 

41) Limit State of Collapse Torsion

42) Limit State of Serviceability :Deflection

43) Limit state of Serviceability : Cracking

ANNEX A: List Of Referred Indian Standards

ANNEX B: Structural Design (WSM)

ANNEX C: Calculation Of Deflection

ANNEX D: Slabs Spanning In Two Directions

ANNEX E: Effective Length Of Columns

ANNEX F: Calculation of Crack Width

ANNEX G: Moments OF Resistance For Rectangular and T-sections

ANNEX H: Committee Composition 

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INDIAN RAILWAY STANDARDS

Indian Railway Standards:-

A railway track may be defined as a composite structure consisting of Rails ,Rail-joints, Fish plates and Bolts, Sleepers, Rail to ‘Sleeper fastenings’, Ballast and other track-fittings. This composite structure acts as an integrated unit and transfers the loads coming on to it from rails to the formation
These “transmitted  stresses should not exceed the permissible stresses of various track components and bearing pressure of soil – sub grade  below”. Since this track structure is not directly embedded into the ground unlike another civil engineering structures so it acts as floating structure (super structure) over the sub-grade foundation and its  design is based on ‘theory of ELASTICITY’.

Railway Track Structures:-

the structure Basically Comprises the following track Components

 1.Rails

2.Sleepers

3.Rail to sleeper-fastenings

4.Ballast

5.Formation

6.Rail joints

The standards for various track components in India have been laid on the basis of permissible speed criteria and traffic density for :1.Broad gauge 2.Meter gauge

*Broad gauge has been classified into 5 groups namely : A,B,C,D and E routes.

*Meter gauge has been classified into 3 groups namely : Q,R and S routes.

Track standards for B.G Routs:-

1.Rails:The rail section of 60kg/m and 52kg/m will only be used on B.G routs. However,90R(90lbs/yd) rails when ever existing may be permitted as an interim measure for speeds not exceeding 130km/hr . 

Sleepers and Sleeper Fastenings:-

these are given in following figure table

Track Standards For M.G routs:-

The track structure for different categories of M.G routes has to be accordance with the track standards given below:

Railway Engineering

 Railway Engineering

here is the definite guide on railway engineering ,

just click on each Concept to read the content.

1) Track Ballast

2) Creep Of Rails

3) Sleepers

4) Interlocking

5) Maintainance of Tracks

6) Track Defects

7) Resistance of tracks

8) Welding Of rails

9) Wear Of Rails

10) Level crossing

11) Railway Signals

12) Indian Railway Standards 

Wear of Rails

Wear Of Rails

Types of wear

1)Wear on head of rail

2)Wear on ends of rail

3)Wear of rail on curve

Wear On Head of the Rail:-

1)Wear on head of rail is due to abrasion on moving rails.

2)Due to grinding action of sand or dust between the rails and wheels of the train

3)When train starts or applies brakes, the wheel just slides on the rails causing wear on the head.

4)Load coming on to a track may exceed the carrying capacity of the section. Thus causing the wear

    in the head of rail.

Water at the ends of the Rails:-

1)It is much greater than the wear on the head of the rail.

2)This type of the wear is resulted due to the blows which the rail receive when the wheel jumps the

   space between the rail ends.

3)The ends are battered by such blows.

4)The contact surface between the sleepers and the rail is worn as the as the effect of these blows

    increased

5)The ballast under the sleepers will loosen due to increase in the intensity of vibrations, also he 

    sleeper will depressed due the displacement of ballast, also the fish plates will get loose under the 

    constant impact of increasing vibrations

Wear of Rail On Curve:-

 1)On the curve the wear of the rail takes place in both inner and outer rails.

2)On the curve, the outer wheel has to move through greater distance than the inner wheel. And the 

     inner wheel has to slide over the inner rail. 

3)As a result of this sliding wear of the inner rail occur because the metal in the rail head is burnt.

4)At the curve, flange of outer wheel will strike the inner surface of the outer wheel due to centrifugal    force. Thus side of the head of rail wears out

Curved Crossing

                                                           Flange of wheel with Slop 1:20

Welding Of Rails

WELDING OF RAILS

Purpose of providing welding:-

1)To increase the length of rail

2)To repair the damage rail thus increase their life.

3)To build up worn out points and rails on sharp curves.

4)To build up the burnt portion of rail head.

Advantages of welding:-

1)It increases the life of rails.

2)It reduces the creep due to increase in length of rail.

3)It reduces expansion effect due to temperature.

4)Welding facilitates track circuiting on electrified tracks.

5)Welding rails provides on large bridges for the span length are helpful as they result in better        performance.

6)The cost of track construction by welding of rails decreases due to less number of rail joints.

TYPES OF WELDING RAILS:-

In India the present practice is to use following types :

1)Short welded rails (SWR)

2)Long welded rails(LWR)

3)Continuous welded rails(CWR)

METHODS OF WELDING RAILS:-

1)Electric arc welding(metal arc welding)

2)Oxy-acetylene welding(gas pressure welding)

3)Flash butt welding

4)Chemical or thermite  welding

Electric Arc Welding:-

In this method the current is passed through the rail and at the same time through  a thin rod known as electrode. As the electrode approaches  the rail ,an electric arc is formed and with its heat the electrode gets melted and finally the molted metal of the electrode gets deposited on the rail providing a firm bond.

Flash Butt Welding:-

In this method powerful current is passed through two rails, the end of which are to be join together. The width of the gap between two rails is varied till both the ends get heated upto a required temperature . Then they are brought in contact with each other resulting in flash

OXY-ACETYLENE Welding:-

In this method intense heat is produced by combining the oxygen and acetylene gas which melts the electrode and deposits  the molten metal on the rail.

This method like electric arc welding is used for repairing damage parts of points  and crossings

                                    here is figure of oxy acetylene welding

Length Of  Welding Rails:-

As a result the use of longer length of rails ensures smooth running of trains and comfort to passengers and therefore the length of rail should be as long as possible. However its length is limited by the following factors:-

1)The length of rail is governed by the facilities available for the manufacture of rails at reasonable costs.

2)The length of rails should be such that they can be transported using longest wagon available with railways.

3)The length of rails is also limited by the available machinery facilities for lifting and handing the rails.

Chemical or Thermite welding:-

It involves use of aluminium and iron oxide, and then mix together in powder form and ignited. After ignition the below chemical reaction takes place 

LEVEL CROSSING

Level Crossing

It means-

A level crossing usually known as a rail road crossing, is an intersection where a railway line crosses a road or path at the same level,  as opposed to the railway line crossing over or under using a bridge or tunnel.

Types Of level Crossing

• Barrier Crossing
• Gated crossing operated by railway staff
• User worked crossing
• Open crossing
• Footpath crossing

1) Barrier Crossing

            Barriers cover either whole road or half the road, there are also warning lights and an alarm. 

2)Gated Crossing;

           Gates are on both sides of the railway, staff close them as trains goes through.

3)User Worked Crossing:

          Gates or barriers are operated by the person using the crossing. These crossings sometimes               have telephones and lights.

4)Open Crossing:

          There are no barriers or gates, however there are road traffic signs at these  crossings. 

5)Footpath crossing:

           Stiles are self-closing gates are on both sides of the railway. Some crossings have  stop lights. 

Safety Measure-

In terms of warning systems, level crossings are either passive crossings which have warnings such as signs, or active crossings which have automatic warning devices such as boom gates, flashing lights and warning tones. Fewer collisions take place at level crossings with active warning systems.

 Today radar sensor systems for automatic level crossing free detection are a cheap way to improve safety of level crossings.

Crossing-

A crossing is a special device provided which  allows the crossing of rails with each other, at an

 angle, without causing any obstruction to the  passage of wheel flanges.

Types;-

1)Vee-crossing or Acute angle crossing;         

              The angle  between the rails of two tracks, i.e, the main track and the branch track is an 

acute angle. This type of crossing is very common in the Indian Railways and consists of the various 

component parts.

2)  Obtuse angle crossing or Diamond crossing;

                     In this type of crossing two acute  angles and two obtuse angles are formed when two

 rail tracks, i.e, one main track and another branch  track crosses each other.

3) Square crossing;

                   A crossing in which the intersecting railway tracks are perpendicular to each other.    

RAILWAY SIGNALS

Railway Signals

1)  A signal is a mechanical or electrical device erected beside a railway line to pass information          relating to the state of the line ahead to train/engine drivers .

 2)The driver interprets the signal's indication and acts accordingly.

 3)Typically, a signal might inform the driver of the speed at which the train may safely proceed or it    may instruct the driver to stop.

Applications and Positioning of Signals:-

Originally, signals displayed simple stop/proceed indications. As traffic density increased, this proved to be too limiting and refinements were added. One such refinement was the addition of distant signals on the approach to stop signals. The distant signal gave the driver warning that he was approaching a signal which might require a stop. This allowed for an overall increase in speed, since trains no longer had to stop on sudden warning.

 Signals are used because of followings:-

1)that the line ahead is clear (free of any obstruction) or blocked

2)that the driver has permission to proceed.

3)the points (also called switch or turnout in the US) are set correctly.

4)the state of the next signal.

5) the train orders are to be picked up by the crew

6)Signals have aspects and indications.

7)The aspect is the visual appearance of the signal

 8)The indication is the meaning

History Of Railway Signalling:-

1825: FIRST RAILWAY LINE FOR GOODS TRAFFIC WAS OPENED BETWEEN   

          DARLINGTON TO STOCKTON (U.K.) UNIFORMED MEN ON HORSES GUIDED THE               TRAIN   . 

1830 : FIRST PASSENGER TRAIN BETWEEN LIVERPOOL AND MANCHESTER              POLICEMAN WERE POSTED AT FIXED INTERVALS.

    1838 : POLICEMEN WERE REPLACED BY FIXED MECHANICAL SIGNALS

1853 :  FIRST TRAIN SERVICE INTRODUCED ON INDIAN RAILWAYS, SEMAPHORE          SIGNALS WERE USED  .

          

Mechanical Signals:-

1)Older forms of signal displayed their different aspects by their physical position.

2)The most common form of mechanical signal worldwide is the semaphore signal.

3)This comprises a pivoted arm or blade that can be inclined at different angles.

4) A horizontal arm is the most restrictive indication (for 'danger', 'caution', 'stop and proceed' or 'stop and stay' depending on the type of signal).

Auxiliary Warning Systems(AWS):-

1)Applies Brakes automatically in case Driver disregards a Red Signal

2)Regulates Train Speed to 15 KMPH on Yellow Aspect 

3)Controls Train speed on RED signal

(Available on WR (1987) & CR Suburban Sections on Mumbai).

Post Mounting:-

When a single track is involved, the signal is normally mounted on a post which displays the arm or signal head at some height above the track, in order to allow it to be seen at a distance. The signal is normally put on the engine driver's side of the track.

Gantry mounting:-

When multiple tracks are involved, or where space does not permit post mounting, other forms are found. In double track territory one may find two signals mounted side by side on a bracket which itself is mounted on a post

Ground Mounting:-

1)Such signals may be physically smaller (termed dwarf signals). Rapid transit systems commonly use nothing but dwarf signals due to the restricted space.

2)In some situations where there is insufficient room for a post or gantry, signals may be mounted at ground level. 

The Types Signalling Systems in Railways

1)Time Interval Method:-

* Trains are Spaced Over an length of a track in such a way that , if the first train stops, the following    train driver should be able to stop the train in sufficient distance without colliding with the first one.

*This type is used where traffic is less and weight of the trains are less.
*This Type of System cannot  be used in Passenger rails since weight and traffic is High

2)Space Interval Method

In this method of “Control Over Movement”, the length of the track is divided in to sections called Blocks. The Entry of a train in to the ‘Block’ is controlled in such a way that only when it is free, a train can be allowed to enter it. This means that between two consecutive trains , there is definite space interval.

Classification And Types and Signals

1)Open Characteristics  :-

it is sub divided into

• Detonating Signals
• Hand Signals
• Fixed Signals

2) Functional Characteristics:-

further sub divided into-

• Stop type signals 
• Warner Signals
• Shunting Signals
• coloured Light Signals

3) Location Characteristics:-

a) Reception Signals-

• Quoter Signals
•  Home Signals

b) Departure Signals-

• Starter signals
• Advance Starter Signals

4) Special Characteristics-

• Repeater or Co-acting Signals
• Routing Signals
• Calling Signals
• Point Indicator
• Modified lower quadrant semaphore Signal
• Miscellaneous Signals

Temporary signals are located as When train is required to stop and the restriction on track is to be kept for more than a day.

1)Temporary signals are located as follows:

•   Caution indication signal
•   Stop indication signal
•   Termination signal

When train is not required to stop and restriction on track is to be kept for more than a day.

    

2)Temporary signals are located as-

• Caution indication signal
• Speed indication signal
• Termination signals.

Resistance of Track

Train Resistance:-

Definition :-The resistance acting at the points of contact of the wheels of the vehicle with the surface of level roadway which opposes the rolling if the wheels over it and thus the movement of the vehicle.

The tractive force developed by the locomotive should be sufficient:

   1. to overcome the train resistance.

   2. to haul the train along the track at the desired  

       speed.                                    

Types of Resisting Forces:-

1. Train resistance.
2. Resistances due to track profile.
3. Resistances due to starting and acceleration.
4. Wind resistance

Train Resistance can be Categories as follows:-
1) Resistance Independent of Speed
2) Resistance Dependent On Speed
3) Atmospheric Resistance

Resistance Independent of Speed:

This resistance is due to following reasons:

1. Rolling Resistance:

   This is due to friction between the metal surface  of rails and the wheels. It consists of following:

   (a) Journal Friction: 

       It is the friction of the locomotive, wagons and   compartment itself. Its amount will depend upon        the type of bearing, the lubricant used and the temperature of atmosphere.

(b) Frictional Resistance:

    It is the resistance offered to the movement of steel       wheels on steel rails. It is maximum at starting and is reduced as motion is caused and it increases as the speed increases.

(c) Track Resistance:

    This is caused due to the wave action of rails

(d)Resistance Due To Internal Parts:

    Its a resistance of the moving parts and locomotive.

Rt1= 0.0016w

    where,

w= weight in tonnes

TRACK DEFECTS

Track Defects 

Track  defects is nothing but the  track  drainage which involves  the interception and  removal of water from, upon or Under the  track .

Sources of moisture in a Railway track   are:-

1)Surface water due to rain, dew or snow.

2)Moisture sucked up by capillary action.

3)Seepage –water from adjacent area.

4)Hydroscopic water or Held-water  

   

Track Defect Due to Improper fitting of nuts and bolts:-

Track defect due to Bolt hole crack:-

Significance of Track defects or drainage The bearing power(strength) and  Stability  of soil are greatly reduced due to the presence of moisture.

Track-defects is important due to following reasons:

1)The modern-track embankment, which are subjected to heavy loads get settled due to the  presence of excess moisture.

2)The excess presence of sub-surface moisture track stability and results in dirty ballast, low joints in pumping sleepers.

3)The presence of surface water and ground water if not properly drained results in recurrent soft spots, unstable banks and cuttings.

4)The bad soil at wet bank when it dries results in shrinkage and cracking up of bank and formation, which further allows ballast from ballast  Section to run into these cracks and get lost to the utility of ballast.

5)Further more, due to dynamic loads on wet-soils, the slush is formed which Is formed out and clogs the ballast.

6)The erosion of soil from the bank, slopes of embankment, cut and hill side is caused due to surface water.

7)In the rainy season, the presence of a badly drained track formation, is the   main cause of accidents due to derailments.

Requirements of Track Drainage systems:-

1)The surface and underground waters should be well away from a track, the banks and cuttings, over or through which they run.

2)The surface water from adjoining land should be prevented from entering the track formation.

3)The side drains should have sufficient capacity and longitudinal slope to carry away all the possible     surface waters.

4)Flow of surface water across the track and along the slopes should not cause erosion of the banks      ad slopes of embankment.

5)Sub-surface water should be efficiently drained off by the sub-surface drainage system.

6)The highest level of ground water table should be well below the level of the subgrade.

7)The drains or pipes should be kept at closer spacing to keep the water table well below the    formation to prevent the capillary rise of water.

Damage Rail Due to improper Welding:-

Due to Crack In Rails:-

MAINTAINANCE OF TRACKS

Necessity of Maintainance:-

Once track is laid, yards are constructed, signaling systems are installed and track is opened to traffic, immediately then, the necessity of maintenance arises due to following reasons:

1)The strength of track structure goes on deteriorating or reducing due to movement of high speed trains, heavy axle loads and repetition of loads. The elastic structure of railway track thus disturbed in alignment, gauge and surface level of rails.

2)The track structure is also subjected to other deterioring effects like rain water, action of sun & winds. The wear & tear of rails, and of rolling stock is then bound to take place due to their adverse effects.

3)The track structure has to bear too many other effects due to curvature, speed & load, particularly on curves, crossing, bridge approaches and at level crossings.

  It is therefore essential to maintain the track in good condition so that trains may run over it safely, comfortably and efficiently at specified speeds. If track is not properly maintained, firstly, this would result in faster wear and tear, rough riding & discomfort to the passengers & then may result in extreme cases of derailments of trains with possible loss of life & property.

The maintenance of railway track can be carried out either manually or by use of mechanical appliances or by combination of both.

In India conventional maintenance is carried out by means of manual labour and hand tools. In America & other developed countries,    mechanical appliances are largely used.

The maintenance of track can be divided into two parts :-

1)Daily maintenance:- Daily maintenance is carried out by the full time staff maintained throughout the year. The use of maintenance gangs, all along the railway track is made. The railway track is divided in suitable sections to 5 to 6 km length. One gang is attached 

to each section for maintaining that section in good condition.

2)Periodic Maintenance:- Periodic maintenance is carried out after an interval of 2 to 3 years. During periodic maintenance , the gauge, level, alignment, points & crossing etc are thoroughly checked, the defects are detected, the causes are determined & finally remdial measures taken.. The track is made perfect condition by removing all its major & minor defects.

The maintenance of track includes the following items of maintenance in good condition.

 (1) Surface of rails.            

 (2)  Track Alignment.

 (3) Gauge.                           

(4)  Proper Drainage.

 (5) Track Components.     

 (6)  Bridges & its Approaches.

 (7) Rolling Stock.            

 (8)   Points & Crossing

 (9) Level Crossings            

(10) Tunnels.

1) Maintenance of surface of rails:- The top surface of two rails should be maintained properly on straight lengths. The top surface should be kept in same plane or level, whether the track is on rising gradient or falling gradient or on a level stretch.
On curves- The outer rail should be kept at prescribed height above the inner rail. i.e proper superelevation should be maintained. Maintenance of surface of rails involves the following operations:-

(A)Packing.
 (B) Surfacing the track.
(C) Boxing & Dressing the track.
(D) Levelling of the track.
(E) Lifting of the track.
 (F) Surface defects & remides.
(G) Spot packing & Track lifting.

2) Maintenance of track alignment:- If the track goes out of alignment. i.e, shifts sideways on the on the straights or at curves due to any one of the following causes, it may result in bad riding & derailments. Maintenance can be done by following operations:-
A) Realignment of straight tracks:- The correction of alignment of straight track is done by 2 methods.
   (i) Bye use of crow bars.
  (ii) By use of track liners.

(B) Realignment of curved tracks:-  Minor adjustments in alignment can be done by means of crow bars or liners as fox straight tracks.
Major adjustments are done by:-
* Checked by human eye.
*Theodolite.
*String line method.

3) Maintenance of gauge:-  Uniformity of the gauge throughout should be properly maintained as it is more important than to provide a proper gauge. With a non-uniform gauge, the riding qualities of the track are adversely affected.
It is maintained by tightening the track fittings & proper maintenance of correct joints, creep anchors etc. instruments used are                            
a) Gauge rod and
 b) Rail brace.

4) Maintenance of proper drainage:- Drainage is most important to ensure smooth riding & longer life of track. The proper drainage of track can be maintained by following methods:-
 (a) Cleaning of ballast
 (b) Cleaning of cess
(c) Surface drainage
(d) Underground drainage.

5) Maintenance of track components:- This includes the maintenance and renewal of rails, track fittings and sleepers.
 In track fittings like Fish plates- The graphiting of fish plates is done for the following purpose:
*To protect the fish-plates against corrosion.
*To allow free expansion and contraction of rails.
*To increase the life of fish plates and bolts.

6) Maintenance of Bridge and its Approaches:- The maintenance of bridge & its approaches over which track passes is of great importance. If accident take place at such spots, it results in huge loss of lives and national property. Maintenance is done by
a) Maintenance of foundation
  b) Maintenance of sub-structure & protection works
c) Maintenance of super structure
d) Maintenance of track on bridge and its approaches.

7) Maintenance of Rolling stock:- The rolling stock, which consists of locomotive ,coaches & wagons, should be maintained in good working condition. For maintaining rolling stock following measures are done:
* Lubrication of all the reciprocating parts & bearings with suitable lubricant should be done.
* All axles after 3 lacs km should be replaced by new once.
* The locomotive boilers should be renewed after every 15 years.

8) Maintenance of points and crossing:- The switches or points are regarded to be the weaker points of the track & most of the derailments occur at points & crossing locations only. so it is maintained by:
* The gauge should be perfect at all places except at the toe where the gauge should be a little slack.
* The ballast should be repacked and screened periodically.
* Adequate drainage must be maintained at all points.

9) Maintenance of level crossing:-In level crossing the road is kept in rail level & grooves are left in road surface along the inner edge of rail for wheel flange. Such an arrangement, packing is not possible without disturbing the surface. To maintain level crossings certain measures are taken:
* The rails and fittings be tarred once a year by opening out the level crossings.
* On level crossing road traffic is low use water bound macadam in the area of crossing, if road traffic is high use bituminous pavement, so track is least disturbed.

10) Maintenance of tunnel:- For maintaining the tunnel certain measures should be taken:
*Portals at the ends should be checked. Any defect in signs of slip above top, crushing or cracking of masonry, percolation of catch water drains into tunnel, bulging etc, should be detected & rectified.
*Al ventilation shafts should be clear of any obstruction and vegetation.
* The level & alignment of track & its approaches are to be checked and rectified.
* The level pillars & reference marks should be checked periodically.

SUMMARY:-
The huge money spent in construction of railway track is a waste, if the track is not maintained properly for comfortable, safe, fast & economic movement of trains over it. Maintaining of track, bridges, points & crossings, tunnels, level crossings etc involves a huge amount of work, employing millions of workers. It should be done efficiently for safety of passengers & goods. The use of mechanical appliances should be encouraged, wherever possible in maintenance operation. 

INTERLOCKING

Interlocking:-

 Introduction:-
1)In railway signaling, an interlocking is an arrangement of signal apparatus that prevents conflicting movements through an arrangement of tracks such as junctions or crossings.
2)An interlocking is designed so that it is impossible to display a signal to proceed unless the route to be used is proven safe.

Definition:-
It is defined as the technique achieved through mechanical or electrical devices or agencies by which it can be ensured that before a signal is taken to off position for the route, which the signal controls, is properly set and held, and the same time all the signals and points, the operation of which may be lead to conflicting the moments are locked against the feasibility of such conflicting moments.


Configuration and Use:-
1)A minimal interlocking consists of signals, but usually includes additional appliances such as switches and derails, and may include crossings at grade and movable bridges. Some of the fundamental principles of interlocking inroute.

2)Signals may not be operated to permit conflicting train movements to take place at the same time

3)Switches and other appliances in the route must be properly 'set' (in position) before a signal may allow train movements to enter that affected.

4)Once a route is set and a train is given a signal to proceed over that route, all switches and other movable appliances in the route are locked in position until either

5)The train passes out of the portion of the route affected

6)The signal to proceed is withdrawn and sufficient time has passed to ensure that a train approaching that route has had opportunity to come to a stop before passing the signal liline.

*Points and signals at junctions must operate in harmony to ensure that no unsafe moves are set up.  The process in known as "interlocking“

*In the example above (Figure), Points C4 and C5 must be set to allow Train 1 to proceed to the main line.

*Points C4 are used to provide "flank protection" to ensure that Signal C2 cannot be cleared.

*Points are normally set in this way to provide such protection even if there is no signal to block.

*Train 1 will proceed to main line without any conflictiline.

*Signal c2 will be so cleared to allow the train 2 to enter the main lline.

*Therefore points c4 & c5 must be set to allow Train 2 to proceed to main line from branch line.

Types of interlocking:-

1)Mechanical interlocking

2)Electro-mechanical interlocking

3)Relay interlocking

4)Entrance-Exit Interlocking (NX)

5)Electronic interlocking

6)Solid-state interlocking

Mechanical interlocking:

 In mechanical interlocking plants, a locking bed is constructed, consisting of steel bars forming a grid

Electro-mechanical interlocking:-

* Power  interlocking may also use mechanical locking to ensure the proper sequencing of levers, but the levers are considerably smaller as they themselves do not directly control the field devices.

Relay interlocking:-

 Interlocking effected purely electrically (sometimes referred to as "all-electric") consist of complex circuitry made up of relays in an arrangement of relay logic that ascertain the state or position of each signal appliance.

Electronic interlocking:-

 Modern interlockings (those installed since the late 1980s) are generally solid state, where the wired networks of relays are replaced by software logic running on special-purpose control hardware.

Entrance-Exit Interlocking (NX):-

          was the original brand name of the first generation relay-based centralized traffic control (CTC) interlocking system introduced in 1936.

Solid state interlocking:-

 (SSI) is the brand name of first generation microprocessor. Based on interlocking development in 1980 by British rail.

Derailing:- improper interlocking

CREEP OF RAILS

Creep of rails:-

Definition:

It is a horizontal movement of rails in a track. It can be minimized but cannot be stopped.               

                            OR

Longitudinal movement of rails in a track .

Cause of creep:-

1)There are three main causes of Creep wave motion of trains.

2)Expansion and contraction of rails due to variation in temperature.

3)Due to starting, accelerating, slowing down (decelerating) and stopping of trains.  

Wave Motion:-

*When train passes on a track, the portion of rail length under the wheel of train will under more stresses and little depression will exist.

*As a result, this depression will cause (set) a wave motion in the rail or track 

Alignment Of Track:
Creep is more on curve track than on a tangent portion (straight track).

Grades:
In upgrades tracks, creep will be less and in down grades track creep will be more.

Direction of movement of trains:
Creep will be more in the direction to which the loaded train moves more.


Extent of Creep:-
1)Creep does not vary at some constant rate. (it is not constant)

2)Creep does not continue in one direction only.

3)Creep for two rails of the track will not be in equal amount.

Result of creep:-
1)Expansion gap is reduced, buckling of track take place.
2)Sleepers are moved out of a square.
3)Crossing points get disturbed.

Creep Prevention:-
Pulling back the rails:
  1)using crow bars and hooks through fish
     bolt holes
   2)slow and tedious process
   3)practicable for only small lengths
Use of steel slippers:
    1)steel through sleepers are best
    2)Increase in number of sleepers can help
 
Using Anchors/Anti-creepers:
 1)4 anchors  per rails if creep is 7.5cm to 15cm/month.
 2)6 anchors per rail if creep is 22.5 to 25cm/month.
 3)Used at levels crossings,in yards and places of heavy brake application.

       SOME IMPORTANT POINTS
1) Should be able to resist the movement of the rails
2)Fixed to good sound sleepers.
3)Should butt against the sleepers.
4) Should not to be used on bridges.

Sleepers

Sleeprs in Railway Track

Sleepers are members generally laid transverse to the rails, on which the rails are fixed to transfer the loads from the rails to the ballast and the subgrade.

Main Functions of Sleepers

1)Holding rails to correct gauge and alignment.

2)Firm and even support to rails.

3)Transferring the load evenly from rails to wider area of ballast.

4)Elastic medium between rails and ballast.

5)Providing longitudinal and lateral stability.

 Requirements of Sleepers

1)Sleepers used should be economical, they should have minimum possible initial and maintenance cost.

2)Operations such as lifting ,packing,removal and replacements of sleepers should be easily handled .

3)The weight of sleepers should have moderate weight.

4)The design of sleepers should be in such a way that the gauge the alignment of track and the levels of the rails can be easily adjusted.

       TYPES OF SLEEPERS

Wooden Sleepers

 2)Metal Sleepers
     a)Cast-iron sleepers
      b)Steel sleepers

3)Concrete sleepers
     a)Reinforced concrete
     b)Pre stressed concrete

Wooden Sleepers

Wooden sleepers are regarded to be best  as they fulfill almost all the requirements of an ideal sleeper.

The life of these sleepers depends upon the ability to resist 

             1.Wear 

             2.Decay

             3. Attack of vermin(white ants)

Advantages/disadvantages of wooden Sleepers

Advantages:-

1)Easy to manufacture and handling.

2)Suitable for track circuited area.

3)Can be used with or without ballast.

4)Suitable for bridges, Points/Crossings.

5)Resists the shocks and vibrations due to heavy moving loads and also gives less noisy track

6)Alignment can be easily corrected.

Disadvantages:-

1) Lesser life.

2)) Liable to damage by beater packing.

3) Difficult to maintain the gauge.

4) Susceptible to fire hazards.

 Description of wooden Sleepers:-

Size of wooden sleepers in mm :

 B.G. : For ordinary track :-

                2750x250x130 (9’x10”x5”) 

Durable and non durable types of sleepers.

Life of Sleeper:

 Durable –19 years (B.G.)/ 31 years (M.G.)

 Non-Durable- 12 to16 years.

Metal Sleepers

Types of cast iron Sleepers:-

1)Pot/bowl Sleepers

2)C S T-9 Sleepers

Advantages of Cast Iron Sleepers:

  i) Lesser corrosion.

  ii) Easy handling due to light weight.

  iii) Higher Scrap value.

 Disadvantages of Cast Iron Sleepers:-

  i) Not suitable for high speed route.

  ii) Difficult to maintain the Gauge.

  iii) Lesser lateral stability.

  iv) Not fit for track circuited area.

  v) Not suitable for mechanical maintenance.

  vi) Tie bars weakened by corrosion.

Usual Defects in CST-9 Sleepers:-

1) Cracks at rail seats or fracture

2) Wear of lug and rail seat

3) Tie bars weakened by corrosion, broken or damaged by falling of wagon parts.

4) Corrosion of tie bars inside the cast iron plates.

Steel Sleepers

C/S:-

Types of S.T. Sleepers
 i) ST sleepers with Pressed up lugs.
 ii) ST Sleepers with loose jaws.
 iii) Bolt and clip type ST Sleepers.

 Disadvantages of ST Sleepers:

 i) Liable for corrosion.

ii) Not fit for track circuited area.

 iii) Develops cracks at rail seat during   service.

 iv) Can only be used for rails for which it is manufactured.

Advantages of ST Sleepers:

 i) Longer life

 ii) Better Stability

 iii) Lesser damage during handling                     /Transport

 iv) Easy to maintain Gauge

  v) Simple Manufacturing Process

  vi) High Scrap value 

Usual defects in ST Sleepers

1) Rusted and corroded metal

2)Cracks at rail seat or near the lugs

3)Elongation of holes

Inspection of sleepers- Over 20 years old

Precautions during maintenance

Reconditioning of sleeper.

Concrete Sleepers:-

  Types of concrete Sleepers:

   i) Prestressed Concrete Sleepers.

        a) PSC-12 for 52 Kg Rails

        b) PSC-14 for 60 Kg Rails

  ii) Reinforced concrete Sleepers.

i)

C/s-

ii)

C/S:-

 Advantages of concrete Sleepers:

 i) Greater stability.

 ii) Track geometry maintained for much. longer duration hence economical.

 iii) Best suited for machine maintenance.

 iv) Suitable for Track circuiting area.

 v)  No chances of damage by fire/            corrosion.

 vi) No possibility of theft.

vii) No chances of gauge widening.

viii) 60 Kg Sleeper can be used for 52 Kg    rail.

 ix) Best suited for LWR track.

  x) Best performance on P & C, S.E.J. Guard rails , Level Crossings, Check rail in curve.

   *Disadvantage :

i)Handling and laying is difficult being heavy.

ii)Damage is very heavy in case of derailment.

iii)No scrap value.

iv)Not suitable for manual packing.

*Conditions for laying Concrete Sleepers:

i) Track should be deep screened.

ii) Cuttings having rocky bed should have clean ballast cushion of at least 300 mm.

iii)On Arch bridges formation cover min. 1 m.

iv) On other bridges ballast cushion not less than 300 mm.

*Spacing Of Sleepers as follows:-

The space between two adjacent sleepers determines the effective span of the rail over the sleepers.
The spacing of sleepers depends on
                 1)   Axle load    
                 2)   Lateral thrust of locomotive
 The number sleepers per rails varies in India from M+4  to  M+7 (where M=length of rail in meteres)

Sleeper Density:-
It is the number of sleepers per rail length.
It is specified as M+x,
  where,
       M = is the length of the rail in meteres
        x = is the number varying according to
                  certain factors.

Factors Governing The Sleeper Density:-
i)Axle load and speed.
ii)Type and section of rails.
iii)Type of ballast and ballast cushion.
iv)Type and strength of sleepers.
v)Nature of foundation.

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