CE-363

Lecture – 6: Rails

Dr. Ankit Gupta, Assistant Professor

Department of Civil Engineering

National Institute of Technology Hamirpur

Lecture Outline

Functions of rails

Type of rail sections

Selection of rail section

Length of rail

Tests on rails

Rail deformation or defects

Rails - Functions

Provide continuous and leveled surface

Smooth surface with lesser friction

Provide lateral guidance to wheels

Bear stresses developed due to vertical

loads, thermal and braking effects

Transmit load to greater area below

Rails - Requirements

Proper Composition of Steel

Economical section

Strength

Durability and

Stiffness

CG near to center of Height

Balancing of tensile and compressive

stresses

Rails – Section

Rails - Requirements

Balanced distribution of material in head, web and foot

Economical and balanced distribution of metal Head

Adequate depth (vertical wear),

Wide (wider running surface),

Lateral stiffness

Height Sufficient vertical stiffness and strength

Rails - Requirements

Economical and balanced distribution of metal Web

Sufficiently thick (resist lateral loads)

Adequate flexural rigidity

Foot wide (stable against over turning),

thickness (withstand vertical and horizontal forces after allowance for corrosion)

Rails - Requirements

Economical and balanced distribution of

metal

Fishing angles – design of bottom of rail

head and top of rails foot

proper transmission of load from rail to

fish plates.

Fillet radii should be large

To reduce the concentration of stresses

Rails – Standard Section

Three types of rails:

Double headed Rail

Dumb-bell section,

Designed to use from both sides

Indentations caused smooth running

difficult

Rails – Standard Section

Three types of rails:

Bull headed Rail

Head was made a little thicker and

stronger than the lower part, by adding

more metal to it.

Rails – Standard Section

Three types of rails:

Flat footed Rail

Also known as ‘Vignole’s rail’ after the

name of inventor.

Under heavy loads the foot was found

sinking in the wooden sleeper

Requires steel bearing plates for load

distribution.

Most commonly used in India.

Rails – Standard Section

Rails – Flat Footed Standard Section

FF rail:

Merits–

Easy to fix

More economical

Greater strength and stiffness

lateral stability

No keys, chairs required

Simple arrangements at points and

crossings

Rails – Flat Footed Standard Section

FF rail:

Demerits

Loosening of fittings

Problems –

Straightening of bent rails

Replacing of rails

Dehogging of battered rails

Rails – Standard Section Designation

Types of sections in use:

British Railways (RBS sections – Revised

British Standard specification)

75R (75 lbs/yd)

90R (90 lbs/yd)

115R (115 lbs/yd)

Rails – Standard Section Designation

Types of sections in use:

Indian Railways

60kg/m (UIC section – Union

Internationale de Cheminde Fer)

52 kg/m (IRS section – Indian Railway

Standard )

Rails – Standard Section Designation

Types of sections in use:

Rail section in use on MG

60R (60 lbs/yd)

75R (75 lbs/yd)

90R (90 lbs/yd)

Rail Section in use on NG

50R lbs/yd

Rails – Comparison of Standard

Sections Strength

Stiffness

Laying and relaying

Arrangement at points and crossings,

etc.

Alignment and stability

Initial Cost

Rails – Comparison of Standard

Sections Rigidity

Inspection

Replacement

Maintenance

Suitability

Rails – Selection of Section

Various considerations in the selection of a rail section are:

Heaviest axle load

Maximum permissible speed

Depth of ballast cushion

Type and spacing of sleepers

others

Rails – Selection of Section

The relationship between weight of rail and heaviest axle load, which the rails have to carry is:

Maximum axle load = 560 x sectional weight of rail (in lbs/yd or kg/m)

Rail - Brand

IR – 90R – TISCO-II 1985 – Basic BASSEMER

Ind. 90lb/yd Company month year Manufacturing

Rlys (60, 75) Process

IRS–52 kg – 710 – TISCO-II 1991 -> OB

IRS section Grade Comp month year Process

52kg/m of rail of steel

(60-UIC) (or 880) making

Rails – Length

Length of rail in use -

12.80 m for BG

11.89 m for MG and NG

Rails – Length

Length is restricted due to:

Ease of manufacturing

Cost

Lack of transportation facility

Lifting and handling facility

Expansion gap requirement

Heavy thermal stresses in long rails

Rails – 90 UTS section

Strength

Ultimate tensile strength is 90 kg/mm2

Higher than the conventional rail

sections having UT strength as 72

kg/mm2

Rails – 90 UTS section

Stresses

Allowable shear stress in 90 UTS section

is 22.5 kg/mm2

This is 18.0 kg/mm2 in 72 UTS section

Maximum shear stress due to BOXN

section is 20 kg/mm2

Rails – 90 UTS section

Hardness

Better wear resistance due to higher

hardness value

Hardness number 270 BHN

Hardness number for 72 kg/mm2 UTS

section is 220 BHN

Rails – 90 UTS section

Service Life

50% higher than conventional 72 kg/mm2

UTS section (medium manganese rail)

Service life of 52 kg (72 UTS section) is

350 GMT

Service life of 52 kg (90 UTS section) is

525GMT

Service life of 60 kg (90 kg/mm2 UTS

section) is 800 GMT

Rails – 90 UTS section

Adaptable for High speed tracks or

heavy load corridors

Lesser wear on curves and gradients

Service life is as high as 50 years

Maintenance life is comparable to the

life of other components like concrete

sleepers, elastic fastenings etc.

Rails – Tests on Rails

Tests for grade 710 rails

Falling weight test

Chemical analysis test

Tensile test

Rails – Tests on Rails

Tests for grade 880 rails

Falling weight test

Chemical analysis test

Tensile test

Microscopic examination

Hardness test (for 10% of the casts)

Hydrogen content in liquid steel test (for

5% casts)

Rails – Deformations / Defects

Deformations

Corrugated or Roaring rails

Hogged Rails

Kinks in Rails

Buckling of Rails

Damaged rails

Rail Failures

Wear on Rails

Corrugation

Rail End Batter

Broken Base

Flaking

Piped Rail

Shelling

Others