1. CE 515 Railroad Engineering
Structures
Source: AREMA Ch. 8.3,8.4
“Transportation exists to conquer space and time -”

2. Bridge Types Timber Trestles Steel Bridge Concrete Bridges
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Concrete Bridges
Moveable Spans
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3. Timber Trestles
Trestle: an open, braced wooden framework that supports the railroad above ground level.
It consists of a series of identical (or nearly so) vertical supports holding up a succession of short spans.
All wood portions of a trestle are designed to be in compression and never in tension.
Lower initial cost, ease of construction and repair.
Found on light density lines, branch lines, short lines and temporary crossing.
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Sources: Trestles – RGS Style Wooden Trestle Construction on the Rio Grande Southern Railroad by Bob Hyman,

4. Timber Trestles Show example on board
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5. Left: Straight Timber Trestle
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Right: Curved Timber Trestle
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6. Typical frame bent trestle
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Pictures Sourceswww.donet.com/.../trestle/d_n_rg_bent.jpg

7. Timber Bent Construction Details
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8. Timber Trestles
Stringers: Structural members extending parallel to the rail and spanning the openings between the bents.
Width: 7” - 10 “. Depth: 14” - 18” Length: 13’ - 15’
Centered under the rail in order that the load distribution is symmetrical
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Stringer Arrangement (Curved Trestle)
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9. Timber Trestles
Caps: 12”-16” in section, extend the width of the bent, commonly 13’-16’ for single tracks.
Transfer loads from stringers to posts or the pile
Sills, at the bottom are caps of the same dimensions , but longer in length.
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10. Timber Trestles
Timber Connectors: metal rings, plates or grids., embedded partly in the faces of overlapping members, transmits loads from one structural member to another.
Split Rings
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Spike Grid Timber Connector
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11. Steel Bridges From short simple beam spans to large through trusses.
The forth railway bridge is the most famous bridge in Scotland. Constructed in 1890 it was the world first major steel bridge.
From short simple beam spans to large through trusses.
Ease of construction and maintenance under traffic
Spans could be cascaded to different location.
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12. Steel Bridges Girder Spans: short span, rolled or welded sections
Practical maximum span length for rolled steel is 50’ (why?), but 70’ have been constructed
For spans over 50’, using a build up section to achieve 150’ to 180’.
Two categories: Deck Plane Girders (DPG) and Through Plate Girders (TPG)
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13. Steel Bridges Deck Plane Girders (DPG):
Design for locations where vertical clearance under bridge is not critical, over stream, non- navigable rivers.
Required a greater total envelope beneath the track structure, thus limiting clearances below
The top flange of the deck plate girder can be utilized to support the deck. No flooring system is required .
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14. Steel Bridges Through Plane Girders (TPG):
Design for locations in tight clearance situations such as over roadways
Less efficient than Deck Plate Girder of equal length: floor system and knee braces
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Google Map Street View: Stange Rd, Ames, IA

15. Steel Bridges Truss Spans: Solution for spans over 150’-180’.
Open web design, top and bottom chord members connected by vertical/diagonal hangers
Two major structural advantages: Primary member forces are axial loads. And, the open web system could use of a greater overall than equivalent solid web girder.
Economy in material and reduce deal load and a more rigid structure (reduce deflection)
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16. Diagrams of various types of truss bridges
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17. Truss Schematic
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Schematic diagram of a through Pratt truss, illustrating the various members and their names. Members in compression are in heavy lines, tension in light
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18. Steel Bridges
Steel Trestles: Similar in construction to a timber trestle except constructed of steel.
Viaducts: Any series of spans, whether arches or steel girders, support on high towers.
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19. Concrete Bridges Arches: build of stone masonry or concrete
Rigid-Frame Bridge: frequently use in connection with grade-separation projects.
Slab Bridges: simple spans resting on abutments and piers. Reinforced concrete, I-beam, T-rail structures.
Concrete Trestles: always precast or cast-in-place with high early strength concrete.
Concrete Girders: 25’-60’ span. Common beam sections are slabs, tees and voided single and double cell boxes.
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20. Concrete Bridges
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21. Moveable Spans
In locations where a fixed bridge cannot provided sufficient clearance (horizontal and vertical) over a specific obstacle such as a navigable waterway.
Also could be found in places that turntables and transfer tables are use to reposition cars and locomotives.
Common forms: Bascule, Lift and Swing
Design considerations beyond structural design:
Integrated lift machinery, fixed span for traffic, simple design, easy installed and maintained, Clearance, specific loading conditions (structural and wind loading).
The duration and frequency of bridge opening and closing must be considered.
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22. Moveable Spans
Bascule Bridges: single leaf spans of either plate girder or truss construction open at one end to provide the navigable opening.
Why not double leaf bascule bridges?
Three basic types: Trunnion, Rolling Lift and Heel Trunnion
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23. Moveable Spans Trunnion Rolling Lift Heel Trunnion
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24. Moveable Spans Swing Span Bridges Vertical Lift Bridges
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25. Other Structures Drainage Structures Retaining Walls Tunnels Sheds
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26. Drainage Structures
Culvert structures for railways do not differ in type or function from highway drainage structure. However, due to the higher live loads, they tend to be significantly sturdier.
Other information please refer the drainage lecture.
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27. Retaining Walls Retaining Walls:
Gravity Retaining Walls: Reinforced concrete or mass concrete structure designed to resist the lateral pressure exerted by material in its rear. Preventing sliding along a horizontal plane.
Crib Walls: made of timber, precast concrete or steel, designed under “gravity wall” theory.
Sheet Piling :sheet pile walls are usually used in soft soils and tight spaces. Sheet pile walls are made of wood, metal or concrete which are driven into the ground.
Mechanically Stabilized Earth (MSE): the earth itself is reinforced to become an integral part of the structure by using reinforced straps, welded wire mesh or geotechnical fabric.
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28. Retaining Walls Sheet Piling Gravity Retaining Wall Crib Wall
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29. Retaining Walls MSE Show example on board

30. Tunnels
The engineering associated with tunnel design and construction is not specific to railway engineering. However, the following aspects need to pay attention for railway engineering:
Overhead Clearance: Over height equipment, superelevation and future grade raises
Side Clearance: For curved tunnel sections to accommodate maximum railcar swingout.
Ventilation and Pressure Equalization: When the internal air pressure increased, the resistance increased. Proper ventilation required to release this pressure build up.
Drainage: To prevent ballast saturation, icing and differential pressure head against the tunnel wall.
Ballast: drainage, alternate track support structures.
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31. Tunnels Rock cut tunnels Soft ground tunnels Show example on board

32. Sheds
Slide or rock sheds are used in mountainous terrain area to protect track and train from the falling rock or debris
Generally constructed with large timbers or cast in place concrete over the track with the slope from uphill to downhill.
Often constructed at the portal or entrance to mountain tunnels.
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33. Questions?
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Thank You