1. CE 515 Railroad Engineering
Railway Structures
Design Considerations
Source: AREMA Ch. 8
bad powerpoints video!
“Transportation exists to conquer space and time -”

2. Loading Design ACI , AISC , AASHTO AREMA Manual for Railway Engineers
Different Types of Loadings

3. Differences From Roadway to Railroad Structures
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Versus
Ask what the class differences are?
They include
Life span railroad design to 100yrs
Heavier live loads
Longitudal loads
Fatigue design
If not mentioned then move on and they should be able to answer by the end of the class (hw question).
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4. Life Span
100 Year Life Span
Due to viable of alternative routes

5. Dead Loads Permanently remaining items supported by the structure
Track is 200lbs/linear ft.
Ballast is 120lbs/ft3
Treated Timber 60lbs/ft3
Not different from roadway design

6. What went wrong
Theodore Cooper consultant for Quebec Bridge collapse in 1907 and again bridge to heavy for it own carrying capacity. (95 deaths)
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7. Live Loads Static and Dynamic effect load of vehicles
Cooper E-Series loading Scheme (E-1)
Bullet make it different from roadway designer for
Cooper –E series later 1800 first insite to design for rail cars live loads. Came before AREA. Incorperated in all major railways in design for two four axle steam locomatives with tenders followed by a uniform load. (not representative of todays standards)
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8. Cooper E-Series Conversions for modern to E-series
Bridge Specific Rating System
Bridges Rated off Limiting Structure
Service Rating vs. Ultimate Rating

9. Live Load 4-Axel Short Span Steel Members (<54ft)
Heavy Intermodal Trains
More Similar Loading to 4-axle coupled cars

10. Impact Loading Dynamic increment and impulsive loads
Caused mostly by flat wheel spots
Designer has no control over imposition
Load amount derived from percent of live load
Flat Wheel on Engine

11. Steel Concrete and Timber Structures Impact Loading
Steel impact load is function of spacing of supporting elements
Differences for prestressed than cast-in-place concrete impact loading calculations
Not taken into account for timber due to material properties and AWS design

12. Centrifugal Force Outward acting force on curve from train
Force bend structure laterally
Steel structure loads laterals and cross frames
Concrete Structures usually stiff enough to resist
Track super elevation offers some compensation
Do roads have to deal with this

13. Lateral Loads
Nosing, hunting action, lurching and damaged rolling stock
Train Hunting
Due to routine train passage
Sssshhh. Be vewy vewy quite. I’m hunting twains.
Road don’t have to deal with

14. Longitudinal Loads Braking and Accelerating Force
Distributed into the supporting structure

15. Wind and Stream/Ice/Buoyancy Loads
Wind loading self explanatory wind force on structure and train
Stream loads are loaded in every way horizontal, vertical, and buoyancy
Vessel collision also a factor

16. In Russia In Soviet Russia wrecked semi is pier.

17. Seismic Loads Induce horizontal and vertical design
Track works as a damping agent
Three defined levels of ground motion

18. Paper clip demo here.

19. Fatigue What most railroad are designed for!
From repetitive stress loadings causing cracks
Often limit designer to bolted connection

20. Fracture Critical Member (FCM)
Any member where failure result in ultimate bridge failure
FCM are held to higher design criteria

21. Deflection, Corrosion and Bearing/Volumetric Changes
Deflection control when long span and high strength materials used
Use of weathering steel popular
Bearing transfer all load from superstructure to substructure while still allowing rotation and translation
Thermal Changes
Where would you not use weathering steal

22. Weathering Steel Bridge

23. Retaining Wall Loads Contain within the right of way
100 year life cycle
Live loading envelope of track structure