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

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

Differences From Roadway to Railroad Structures Image from http://www.fra.dot.gov/us/content/4 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). Image from http://images.google.com/imgres?imgurl=http://upload.wikimedia.org/wikipedia/commons/

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 Not different from roadway design

What went wrong Theodore Cooper consultant for Quebec Bridge collapse in 1907 and again 1916. bridge to heavy for it own carrying capacity. (95 deaths) 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) 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 1925. design for two four axle steam locomatives with tenders followed by a uniform load. (not representative of todays standards) 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 Do roads have to deal with this

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 http://www.flickr.com/photos/leadegroot/2311723124/

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 In Soviet Russia wrecked semi is pier. http://englishrussia.com/?m=200612&paged=5

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

Paper clip demo here.

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 Where would you not use weathering steal

Weathering Steel Bridge

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