CE 515 Railroad Engineering

CE 515 Railroad Engineering
Railway Structures
Design Considerations
Source: AREMA Ch. 8
bad powerpoints video!
“Transportation exists to conquer space and time -”
Loading Design
• AREMA Manual for Railway Engineers
• Different Types of Loadings
Differences From Roadway to Railroad
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Life Span
• 100 Year Life Span
• Due to viable of alternative routes
Dead Loads
• Permanently remaining items supported by
the structure
• Track is 200lbs/linear ft.
• Ballast is 120lbs/ft3
• Treated Timber 60lbs/ft3
What went wrong
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Live Loads
• Static and Dynamic effect load of vehicles
• Cooper E-Series loading Scheme (E-1)
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Cooper E-Series
Conversions for modern to E-series
Bridge Specific Rating System
Bridges Rated off Limiting Structure
Service Rating vs. Ultimate Rating
Live Load 4-Axel
• Short Span Steel Members (<54ft)
• Heavy Intermodal Trains
• More Similar Loading to 4-axle coupled cars
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
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
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
• Track super elevation offers some
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.
Longitudinal Loads
• Braking and Accelerating Force
• Distributed into the supporting structure
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
In Russia
Seismic Loads
• Induce horizontal and vertical design
• Track works as a damping agent
• Three defined levels of ground motion
• What most railroad are designed for!
• From repetitive stress loadings causing cracks
• Often limit designer to bolted connection
Fracture Critical Member (FCM)
• Any member where failure result in ultimate
bridge failure
• FCM are held to higher design criteria
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
Weathering Steel Bridge
Retaining Wall Loads
• Contain within the right of way
• 100 year life cycle
• Live loading envelope of track structure

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