ce 515 railroad engineering railway structures design considerations source: arema ch. 8...
Post on 22-Dec-2015
222 Views
Preview:
TRANSCRIPT
CE 515 Railroad Engineering
Railway StructuresDesign ConsiderationsSource: AREMA Ch. 8
“Transportation exists to conquer space and time -”
bad powerpoints video!
Loading Design
• ACI , AISC , AASHTO
• AREMA Manual for Railway Engineers
• Different Types of Loadings
Differences From Roadway to Railroad Structures
Versus
Image from http://www.fra.dot.gov/us/content/4
Image from http://images.google.com/imgres?imgurl=http://upload.wikimedia.org/wikipedia/commons/
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
Image from : http://www.time.com/time/photogallery/0,29307,1649646_1421688,00.html
Live Loads
• Static and Dynamic effect load of vehicles
• Cooper E-Series loading Scheme (E-1)
Image from: http://www.tpub.com/content/armytransportation/TI-850-02/TI-850-020112.htm
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
resist• Track super elevation offers some
compensation
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.
http://www.flickr.com/photos/leadegroot/2311723124/
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
Seismic Loads
• Induce horizontal and vertical design
• Track works as a damping agent
• Three defined levels of ground motion
Fatigue
• 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
top related