# RAILWAY ENGINEERING – GEOMETRIC DESIGN

RAILWAY ENGINEERING might be a multi-faceted engineering discipline handling the look, construction, and operation of each form of the rail transport system. It encompasses a large range of engineering disciplines, as well as applied science, computer engineering, electrical engineering, mechanical engineering, industrial engineering, and production engineering. excellent several alternative engineering sub-disciplines are known as upon.

Railway systems entail rather more than a train and a track. they’re supported by advanced technical and operational solutions, managing incessantly dynamic demands for a lot of efficient transport for each passenger and freight a day. every system consists of the many elements that have to be properly integrated: from trains, tracks, stations, sign and management systems, through watching, maintenance, and also the impact on cities, landscape, and other people. This integration is that the massive challenge and also the supply of the many train delays, inconvenient connections, and alternative problems that impact our society.

Railway engineering offers substantial economic benefits, energy efficiency, and environmental and safety edges to nations everywhere the world, and rail is widely viewed as a significant part of the integrated facility for property and resource economical societies of the longer term. there’s substantial demand for engineers with integrated information of railway subsystems (infrastructure, vehicles, and traffic control) who perceive the way to maximize the performance of the complete system.

## Important Terms

1. Gauge- Inner distance between two rails, or distance between running faces of two rails. Different gauge size
a) Broad Gauge (BG)- 1.676 m
b) Meter Gauge (MG) – 1.0m
c) Narrow Gauge (NG) -0.762 m
2. LWR (Long welded rails)- In order to avoid the expansion joints in rails welding of rails is done & stress-induced is arrested by fixtures and sleepers.

If one sleeper gives R resistance force. Then no. of Sleepers required to Resist the Force developed due to expansion of rail.

n= As×α×T×Es/R,
where As is a cross-section of one rail,
T = temperature in degree centigrade
Es = modulus of Elasticity of steel
α = coefficient of thermal expansion

Total minimum length of LWR = 2 ( n-1) S
Where S is the spacing of sleepers
3. Composite Sleeper Index – It is an index to determine the suitability of wooden sleeper for
use in railway track.
CSI=(S+10H)/20 ;
Where,
S= Strength index of timber at 12% moisture content
H= Hardness index of timber at 12% moisture content.
The minimum value of CSI for Track Sleeper is 783

4. Sleeper Density – Number of sleepers required to be used for one rail length
Values of Sleeper density varies between (n+3) to (n+6)
n = the length of one rail in the meter.

5. Minimum Depth of Ballast Cushion – Md= (S-W)/2, Where S is Center to Center distance between Sleepers, W is the width of one sleeper.

6. Safe Speed on Curve (By Martin’s Formula)
a) On transitioned Curved- If Vmax is in Kmph and R radius is in meter

For BG and MG

For NG

b)On non- transitioned Curved- It is 80% of Transitioned curve value

For BF and MG

For NG

For High-Speed Trains

7. Relation of Radius of Curve/Degree of Curve

8. Versine of Curve

For a chord length AB, Versine (V) of the curve would be =

9) Super elevation or Cant- It is provided to counter the effect of Centrifugal force, to reduce the chance of derailment & to reduce the wear and tear of rails.

Where G is gauge in meter, V is speed in KMPH, R is radius of curve in meter
If cant is designed for equilibrium speed, then Veq is determined using
Veq=3/4 of maximum speed (Condition V>50kmph)
Veq=Vmax (Condition V<50kmph)

Maximum limit of Super elevation
a) BG if V<120 kmph- =16.5cm
b) BG if V>120 kmph- =18.5cm
c) MG- =10cm
d) NG- =7.6cm

10) Cant deficiency- From above values we can understand that for high speed trains cant requirement is more, but actual provided value is less (as designed for equilibrium speed), hence there is deficiency of cant.

Maximum limit of Cant deficiency
a) BG if V<100 kmph- Cd=7.6cm
b) BG if V>100 kmph- Cd=10cm
c) MG- Cd=5.1cm
d) NG- Cd=3.8cm Relation between cant and cant deficiency

, is used for calculation and used for Vactual calculations.

11) Negative Super Elevation When a branch track is diverging from a main curved track in opposite direction, outer rail is provided at lower elevation with respect to inner rail, it is called negative super elevation.

### Railway Terminology

##### RAILWAY ENGINEERING – GEOMETRIC DESIGN

RAILWAY ENGINEERING – GEOMETRIC DESIGN