1. CE 515 Railroad Engineering
Track
Source: Armstrong Ch 3, AREMA Ch. 3, REES Module 2
“Transportation exists to conquer space and time -”

2. Track Structure Basics
Responsible for supporting load from locomotives and train cars
Transforms loads applied by the wheel to a moderate pressure that the foundation can maintain without failure
Responsible for guiding locomotive and train car movement
Typical parts of structure:
Wheel
Rail
Tie plates or other fastening system
Ties
Ballast
Sub-ballast
Sub-grade

3. Loading of the Track Structure
Types and Sources of Load Application:
Vertical Loads
Weight of vehicle
Additional loads accompanying motion of vehicle
Longitudinal Loads
Mechanical forces from train actions
Changes in temperature
Lateral Loads
Flanging of locomotive or train car against rail around curves
Side-to-side movement of train at high speeds
Sources of Loads
Figure 3-7 Armstrong, pg 28

4. Load Distribution Analysis/Behavior
Figure 3-6, Armstrong, pg 27
Load distribution through structure
Structure typically must support a 36,000# (from REES module) load from each wheel
“typical 4-axle rail car”
Load transfer path
Wheel
Rail
Tie plates/other fastener system
Ties
Ballast
Sub-ballast
Sub-grade

5. The Rail Most expensive, valuable part of structure Key Functions
Transfer weight from wheels to ties
Provide smooth running surface
Guide wheel flanges
From wood to high strength “T”
Necessity for evolution
Today’s rail accommodates up to 1 billion gross tons of traffic daily
Figure 3-8, Armstrong, pg 30

6. The Rail, cont’d How is rail identified? Can’t last forever..
Weight
90 – 141 lbs/yd
AREMA, AAR (ARA), ASCE set code standards
Size
Base (5.5” – 6”)
Height (6” – 8”)
Can’t last forever..
Rail wear, corrugation, fatigue and other defects
history.howstuffworks.com

7. Rail Joints Rail manufactured in sections Typical Joints
Joints bolted together
What’s that racket?
Typical Joints
Standard
Compromise
Insulated
“Rock and Roll IS noise pollution”
For rail
reference.findtarget.com
Continuous-Welded Rail
Welding can be applied in plant or field
Electric butt and thermite welding
Eliminates joints and maintenance costs
However, is not free to expand or contract…
acwr.com

8. CWR Disadvantages “Sun Kinks” or Rail buckling (above)
telegraph.co.uk
“Sun Kinks” or Rail buckling (above)
CWR application limited to narrow temp. range
Pull-aparts – caused by excessive tensile stresses
Less of a problem than buckling (don’t cause derailments)
Both taken into consideration

9. Ties Key Functions From Stone to Wood Today typically made from Timber
Transmits loads from the rails to ballast section
Provide resiliency and absorption of impact loads
Maintain gage
From Stone to Wood
Today typically made from
Timber
Concrete
Steel
Composites

10. Crosstie Options Timber (hardwood, softwood) Concrete
Pressure treated with creosote to extend its life
“Nailable”
Sufficient resiliency to cushion impact of wheels on rail
Reduces forces from load applied on track
Concrete
Weighs 3 to 4 times as much as timber ( # vs 200#)
However, more stable system
Better for severe service
High speed passenger
Heavy tonnage haul lines
For use on slow, heavy tonnage large curves
Good for parts of world that are low in timber supply
Requires more complex fastening system
waterquality.montana.edu
lbfoster.com

11. Crosstie Options, cont’d
Steel
Require less ballast
Plant operations
Beneficial in tunnels with limited headway clearance
Not widely popular
Problems with shunting of signal current flow to ground
Fatigue cracking
Composites
Extensive research to create new ties
Rubber, plastic, polymers
Mostly research based, some used in light tonnage rail
Not much known on benefits/ disadvantages yet
narstco.com
rti-railroad-tie.com

12. Complete the System
Final resistance measures to defer lateral and longitudinal loads
Tie Plates
Provide smooth, uniform bearing surface between rail and tie
Helps in maintaining gage
Not always used
Single vs. double-shoulder plates
Rail Anchors
Control “rail creep”
Connected directly between rail base and tie
Fasteners
Reduce movement between tie plate and tie
Prevents plate cutting into the tie
Spikes
Maintain gage between running rails
Secure rail to tie
ossloh-track-material.com
commons.wikimedia.org

13. Complete the System, cont’d
Elastic Fastener System vs. Cut-Spike Systems
Elastic fastener system
Same system used on concrete crossties
Alternative to cut-spike
Been adapted for use on timber crosstie track
Stronger track structure
Eliminates need for rail anchors
Eliminates “spike killing” on wood ties
Good for areas where rail is changed out repeatedly - curves

14. Ballast Substructure What about Ballast? Just any Crushed Rock?
Layer of crushed rock under ties
Anchors ties and provides stability
Distributes reduced loads to sub-grade
Provides immediate drainage to structure
Allows for easy maintenance
Provides essential elasticity and resilience to structure
Just any Crushed Rock?
No, tougher and harder rock is necessary
Eliminates possible shattering under loading conditions
Durable and resistant to abrasion and weathering
Low first cost
Typically – granite (preferable), limestone, blast furnace slag
Is a Sub-Ballast always needed?
No, only if poor sub-grade exists
Sub-ballast will be layer of smaller sized rock
Use of geotextile fabric between layers of ballast used to spread load out more and maintain clean ballast
Especially in use where extreme loading conditions exist

15. Ballast Substructure, cont’d
Basic Ballast/Sub-ballast dimensions (below)
Effects of Unclean and Inefficient Ballast
Fouled ballast will freeze in winter
Higher stresses in rail and tie system once thawed in spring
Cause rapid deterioration of track geometry
Need to be maintained and/or replaced throughout life
Ballast Cleaner in Action
Ballast Cleaner at Work

16. Rail Construction Evolution
New Construction Technology
Fully Automatic Railroad Construction Machine
Plasser and Theurer Railroad Workmachine Part 3
Discovery Channel - Building the Biggest Railway 2/6
Discovery Channel - Building the Biggest Railway 3/6