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Railway Engineering

Railway Engineering - Transportation Engineering

Rails: 

  • The rails on the track can be considered steel girders for the purpose of carrying axle load.
  • Rails transfer Axle load to the subgrade through sleepers and ballast. 
  • Rails convert the rolling loads (moving wheel loads of train) into point load, which acts on the sleepers.
  • Sleepers convert point load into the distributed load.
  • Ballast convert line load is a uniformly distributed load.
  • Rails are made up of high carbon steel, to resist wear and tear.
  • On points and crossing rails of medium carbon and high manganese steel is used.
  • In India, rails are manufactured by open hearth or duplex process.



Requirements of Rails:

Rails act as continuous girders carrying axle loads. They should meet the following requirements to serve intended purposes:

  • They should be the proper composition of steel and should be manufactured by open hearth or duplex process. 
  • The vertical stiffness should be high enough to transmit the load to several sleepers underneath. The height of rail should, therefore, be adequate. 
  • Rails should be capable of withstanding lateral forces. The large width of the head and foot endows the rails with high lateral stiffness.
  • The head must be sufficiently deep to allow for an adequate margin of vertical wear. The wearing surface should be hard. 
  • Web of rails should be sufficiently thick to bear the load coming on it and should provide adequate flexural rigidity in a horizontal plane. 
  • The foot should be wide enough so that rails are stable against A overturning, especially on curves. 
  • The bottom of the head and top of the foot of rails should be so shaped as to enable the fishplates to transmit the vertical toad efficiently from the head to the foot at rail joints. 


  • Relative distribution of material of rail in head, web, and foot must be balanced for smooth transmission of loads. 
  • The center of gravity of the rail section must lie approximately at mid-height so that maximum tensile and compressive stresses are equal.
  •  The fillet radii must be large to reduce the concentration of stresses. 
  • To allow an adequate margin of vertical wear, the head of the rail must be sufficiently deep, max. wear of head allowed is  10 mm.
  • The minimum tensile strength of rail should be 72 Kg/mm2.
  • In India, rails are tested by falling weight test or tup test.
Types of Rails:

1. Double-Headed Rails (D.H. Rails):

  • These rails were used in the beginning.
  • The idea behind these was when the head will be worn out in the course of time, the rail can be inverted and reused.

  • In the lower part, the indentations were so formed that smooth running over that surface at the top was impossible, so the idea got failed.

    Double-headed rails(D.H. Rails) - Railway Engineering

2. Bull-Headed Rails (B.H. Rails):

  • In B.H. rails the head was made a little thicker and stronger than the lower part.
    Bull Headed Rail- Railway Engineering

3. Flat-Footed Rails (F.F. Rails):

  • F.F. Rails are also called Vignole's rails after the name of the inventor.
  • Bearing Plates are used between the sleeper and rail at rail joints.
  • These rails are designated by wt. of rail per unit length.
  • 52 kg/m or 52 MR and 60 kg/m or 60 MR F.F. rails are used in India.
  • 52 kg rail is suitable upto speed of 130 kmph and 60 kg rail is suitable upto speed of 160 kmph. 
    Flat Footed Rail- Railway EngineeringMetric Rail (HR) as per IRC Indian Railway Standards - Railway Engineering


Comparison between Flat Footed Rail and Bull Headed Rails- Railway Engineering

Note: Flat-footed rails are most commonly used in India


Length of the rails:

  • Rails of larger lengths are preferred to smaller lengths for more strength and economy. 
  • Joints between Rails are the weakest points of the railway track and the cost of fasteners is also high. 
  • In longer rails, no. of joints and fish plates are less thus lesser maintenance cost. 
  • Rail's length is restricted due to transportation limitations and due to more gaps required for expansion joints 
  • Rail length of 12.8 m (say 13 m) for BG tracks and rail length of 11.89 m (say 12 m) for MG tracks are used by Indian Railways.

Some Other Important Points:

  • The ratio of wt. of rails to wt. of the locomotive (axle load) is 1:1510.
  • When wear of head exceeds 5% of total wt. the rail must be replaced. 
  • On the curves, check rails parallel to the inner rail can be introduced to control wear.
  • Check rail prevents the wear of outer rail. 
  • Check rail, is used if curves (degree of curves) is more than 8° for BG and more than 14° for M.G.

Permanent Way or Railway Track:
  • A combination of rails, fitted on sleepers, and resting on ballast and subgrade is called the railway track or permanent way.
  • Some time temporary tracks are also laid for the transportation of the material. So to distinguish final alignment with the temporary tracks, the term permanent track is used.
  • On the curve superelevation is maintained by the ballast and formation is leveled.




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