CE 515 Railroad Engineering

1. CE 515 Railroad Engineering Structures Source: AREMA Chapter 8 Introduction and Major Bridge Components “Transportation exists to conquer space and time -”

2. Introduction • Railway structures serve one of two functions: • Support the track itself • House railway operations • What are some examples of railway structures?

3. Types of Structures • Source: http://northernsong.wordpress.com/2009/09/02/construction-and-value/ Track Carrying Structures • Bridges • Trestles • Viaducts • Culverts • Scales • Inspection Pits • Unloading Pits • Source: http://switzerlandinview.wordpress.com/2007/10/29/landwasser-viaduct// • Source: http://www.nationalcorridors.org/df/df08192002.shtml

4. Types of Structures Ancillary Structures Drainage Structures Retaining Walls Tunnels Snow Sheds Repair Shops Loading Docks Passenger Stations Platforms Fueling Facilities Towers Catenary Frames • Source: http://www.gatewaynmra.org/articles/tunnel-liner.htm • Source: http://home.att.net/~berliner-ultrasonics/rr4.html

5. Structural Design: Loads • Dead Loads—self weight • Live Loads—traffic induced • Dynamic Loads—traffic induced • impact, centrifugal, lateral and longitudinal forces. • Environmental Loads—weather • wind, snow and ice, thermal, seismic, and stream flow loads

6. Structural Design: Railway vs. Highway • Railway structures must perform under: • Heavier loads • Live load dominates design • Longer service life • Dissimilar maintenance • Fatigue and maintenance hold much higher influence

7. Major Bridge Components Substructure Superstructure Bridge Deck • Source: http://upload.wikimedia.org/wikipedia/commons/thumb/3/37/Forth_Rail_Bridge_Pier.jpg/800px-Forth_Rail_Bridge_Pier.jpg • Source: http://www.michaelminn.net/america/johnstown,_pa/2008-11-05_13-23-45_corrected.jpg • Source: http://farm4.static.flickr.com/3078/3098004504_94f659cddf.jpg

8. Substructure • Abutments, Piers, and Foundations • Transmits loads to underlying soil: • Dead Load • Live Load • Environmental Forces • General Composition • Pile Foundations • Spread Footings • Piers and Abutments • Any combination of the three

9. Substructure: Soil and Geologic Conditions • Structure stability is dependant on soil conditions • Design Reference: • Chapter 8, Part 22 of AREMA Manual for Railway Engineering

10. Substructure: Piling • Further distinguished by purpose • IE, fender piles—protect masonry structures • Capacity based on allowable stress • Established in AREMA Manual Chapter 7, Part 2 • Two general classifications of piling: • Bearing/Friction Piles • Sheet Piles

11. Bearing/Friction Piles • Pile is driven, jetted, or otherwise embedded on end into the ground. • Timber Pile Driving Video • Concrete • Steel • Source: http://www.fhwa.dot.gov/infrastructure/tccc/tutorial/piles/pile03d.htm

12. Sheet Piles • A continuous connected line of piles driven together to form a wall. • Resists lateral pressures • Timber and concrete • Tongue-and-groove construction • Steel • Interlocking • Source: http://geofoam.syr.edu/GRC_rt23a.asp • Source: http://www.ptbppid.com/services.html

13. Timber Piles • 15-20 ton capacity • 20-60ft lengths • Splicing • Straightness of pile is critical • Crooked piles produce eccentric loading • Decay • Moist ground/submerged—immune to decay • Air exposure—decay within a few years

14. Timber Piles • Wood types • White Oak, Cypress, and Long-Leaf Yellow Pine • Two classes of timber piles: • First Class—railway bridges • Second Class—cofferdams, falsework, temporary work, and light foundations • Source: http://www.ehansch.com/bridges.html

15. Steel Piles: H-Beam Sections and Tubular Sections • Two classifications of steel piles: • Rolled “H” • Tubular sections—usually concrete filled

16. H-Beam Sections • Rolled metal sections with wide flanges • Designed for pile loading • Strength in tension and compression • Smaller cross-sectional area • Well adapted for deep construction • Minimal displacement • Breakage immunity • Susceptible to corrosion • Source: http://www.roadstothefuture.com/I64-I295-Int-Mod-Photos-Nov07.html

17. Tubular Sections • Typically filled with plain or reinforced concrete • Possess large MOI, suitable to resist lateral forces • Source: http://www.geodrillinginternational.com/__data/assets/lead_thumbnail/0012/178698/Aarsleff-plead.jpg

18. Concrete Piles: Precast and Cast-In-Place • Suitable for large, heavy structures • Very durable, also immune to decay • difficult to splice • 40-50 ton capacity • 10-24 inch diameter • 20-60 ft length • Two classifications of concrete piles: • Precast Concrete Piles • Cast-In-Place Concrete Piles

19. Precast Concrete Piles • Driven, much like timber and steel piles • Two forms of cross sections: • Uniform cross section • If piles bear on hard stratum or act as columns • Tapered cross section • If embedded in soft material or derive support from skin friction • Taper as much as ¼-in per foot to a minimum 8-in diameter • Source: http://www.archiexpo.com/prod/samer-spa/precast-reinforced-concrete-driven-pile-61928-156368.html

20. Cast-In-Place Concrete Piles • Formed by pouring concrete into a metal shell or tube previously placed • Cannot be damaged by transport/driving • Must allow for curing time • Reinforcement necessary when subject to lateral forces • Placed as single unit • Source: http://ci.billings.mt.us/PhotoView.aspx?PHID=233

21. Substructure: Abutments • Three primary types of abutments: • Wing • Breast • “U”-Shaped • Arch • “T”-Shaped • Other Modifications • Buried and Hollow or Box

22. “Wing” Abutments • Used when embankment is not a high fill • Simple breast wall, flanked by wings • Wings turn back at ~30+ degrees • Modification: • Breast • Source: http://74.125.155.132/search?q=cache:25pomvsrG-cJ:chestofbooks.com/architecture/Cyclopedia-Carpentry-Building-4-6/234-Abutments.html+U-shaped+abutment&cd=3&hl=en&ct=clnk&gl=us

23. “U” Abutments • Two wings that extend backwards at right angles to the face • Sometimes modified into the “pulpit” • Source: http://74.125.155.132/search?q=cache:25pomvsrG-cJ:chestofbooks.com/architecture/Cyclopedia-Carpentry-Building-4-6/234-Abutments.html+U-shaped+abutment&cd=3&hl=en&ct=clnk&gl=us

24. “T” Abutments • Similar to breast type abutments with addition of a stem • Stem stabilizes the breast • Bridges the slope of the embankment

25. Substructure: Piers • Contribute intermediate support for muti-span brides • Rest on stable, unyielding foundations below frost line • Placed below scouring elevation • Source: http://www.artsintransit.org/pages/organizational.html

26. Superstructure • Portion of a bridge supporting and conveying the live load to the substructure on which it rests • Two general classes: • Steel Spans • Concrete Spans • Design governed by the nature of the obstacle being crossed • Source: http://www.historicbridges.org/pennsylvania/sharonrr1/

27. Bridge Decks • Portion of a railway bridge that supplies a means of carrying the track rails • Two general classes: • Open Deck Bridges • Rails anchored to ties directly on the bridge floor • Ballast Deck Bridges • Rails anchored to ties supported in a ballast section

28. Open Deck Bridges • Less costly • Free draining • Use over streets requires additional measures • Establishes a permanent rail elevation • Source: http://www.vwindependent.com/Stories%20for%20April%202008.htm

29. Ballast Deck Bridges • Provides better riding track • Consistent track modulus on bridge • Reballasting concerns • Provide protection for activities below • Source: http://www.hothamvalleyrailway.com.au/news.htm

30. Superelevation on Decks • Sloping the pile or post cut-off of timber piles • Tilting the superstructure • Framing the floor system out of level (rare) • Tapering ties along bridge • Increasing ballast depth under one rail

31. Bridge Tie Framing • Bridge ties are dapped when they contact supporting steel • Maintains alignment across bridge • AREMA Dap Recommendations: • Dap not to exceed flange width by more than ½ in. • Dap be not more than ½ in. • Ties are typically 10-12 feet by 8-in x 8-14-in

32. What is Dapping? “The term "dapping" refers to a notch in a timber (or in this case, a crosstie) in preparation to receive another part of timber. Dapping is a popular practice in bridgework when railroads need to shim ties up for superelevation (when the outer rail is vertically higher than the inside rail to neutralize centrifugal force). For example, if the outer rail on bridgework is 12 inches high and the inner rail is 9 inches high, railroads can cut grooves (or dap out) in sections of the timber, allowing the height difference to taper off from the high end to the low end of the timber over the distance of the timber.”-- Sayre C. Kos • Source: http://www.trains.com/trn/default.aspx?c=a&id=4179

33. Ballast and Bridge Floors • Ballast • Typically 6-12 inches in depth • Bridge Floors • Concrete segmented girder spans • Creosoted timber planks and timber or steel floor • Reinforced concrete slabs • Structural plates supported by strings • Structural troughs

34. Other Bridge Deck Considerations • Drainage • Anchorage of Bridge Ties • Guard Timbers • Inner Guard Rails

35. Questions