CE 515 Railroad Engineering
Structures
Source: AREMA Ch. 8.3,8.4
“Transportation exists to conquer space and time -”
Timber Trestles
Bridge Types
Steel Bridge
Picture
sources:
http://me
mbers.cox.
net/sn3nu
t/trestles%
20part%20
1.htm
Concrete Bridges
Picture
Sources
:
http://u
pload.w
ikimedi
a.org/w
ikipedia
/comm
ons/8/8
5/Forth
railbrid
gefroms
outhqu
eensfer
ry.jpg
Moveable Spans
http://f
arm1.st
atic.flick
r.com/2
25/493
880918
_adc1e
46808.j
pg
http:/
/en.wi
kipedi
a.org/
wiki/Fi
le:Peg
asus_
bridge
_new.j
pg
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.
Sources: Trestles – RGS Style Wooden Trestle Construction on the Rio Grande Southern Railroad by Bob Hyman,
http://members.cox.net/sn3nut/trestles%20part%201.htm
Timber Trestles
Picture sources: http://www.railtrails.org.au/states/trails.php3?action=trail&trail=91&gallery=666
Left: Straight Timber Trestle
Right: Curved Timber Trestle
Pictures sources: http://www.jvmodels.biz/ho_scale_models.htm
Typical frame bent trestle
Pictures
Sourceswww.donet.com/.
../trestle/d_n_rg_bent.jpg
Timber Bent Construction Details
Picture Source: http://members.cox.net/sn3nut/trestles%20part%201.htm
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
Stringer Arrangement (Curved Trestle)
Picture sources: http://members.cox.net/sn3nut/images/Trestle%20Clinic%20Images/Figure%207.gif
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.
Picture sources:
http://members.cox.net/sn3nut/trestles%20part%2
01.htm
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
Spike Grid Timber Connector
Picture sources:
http://clevelandsteel.thomasnet.com/category/shea
r-plates-split-rings-spike-grids
Picture sources:
http://members.cox.net/sn3nut/trestles%20part%2
01.htm
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.
Ease of construction
and maintenance
under traffic
Spans could be
cascaded to different
location.
Picture Sources:
http://upload.wikimedia.org/wikipedia/commons/8/85/Forthrailbridgefromsouthqu
eensferry.jpg
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)
Steel Bridges
Deck Plane Girders (DPG):
Design for locations where vertical clearance under bridge is not critical, over stream, nonnavigable 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 .
http://www.historicbridges.org/other/annarbor/PICT3639.JPG
http://www.historicbridges.org/other/annarbor/AnnArborRR51.jpg
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
Google Map Street View: Stange Rd, Ames, IA
http://www.historicbridges.org/other/annarbor/AnnArborRR21.jpg
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)
Picture source:
http://okbridges.wkinsler.com/builders/oklahoma.html
Diagrams of various types of truss bridges
Pictures source: http://okbridges.wkinsler.com/technology/index.html
Truss Schematic
Schematic diagram of a through Pratt truss, illustrating the various members and their
names. Members in compression are in heavy lines, tension in light
Pictures source: http://okbridges.wkinsler.com/technology/index.html
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.
http://data2.collectionscanada.gc.ca/ap/a/a029691.jpg
http://okbridges.wkinsler.com/builders/oklahoma.h
tml
Concrete Bridges
Arches: build of stone masonry or concrete
Rigid-Frame Bridge: frequently use in connection with gradeseparation 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.
Concrete Bridges
http://switzerlandinview.wordpre
ss.com/2007/10/29/landwasserviaduct/
http://www.morscher.c
om/rr/1977/19770618
_22.jpg
http://farm1.static.flickr.com/225/
493880918_adc1e46808.jpg
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.
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
Moveable Spans
Trunnion
http://en.wikipedia.org/wiki/File:
MovableBridge_draw.gif
http://en.wikipedia.org/wiki/File:
Lake_Erie_Drawbridge.JPG
Rolling Lift
Heel Trunnion
http://en.wikipedia.org/wiki/File:
MovableBridge_roll.gif
http://etc.usf.edu/clipar
t/6200/6259/bridge_8.
htm
http://en.wikipedia.org/wiki/File:
Pegasus_bridge_new.jpg
http://en.wikipedia.org/wiki/File:
Mystic_River_Bridge.jpg
Moveable Spans
Swing Span Bridges
http://en.wikipedia.org/wiki/File:
MovableBridge_swing.gif
http://en.wikipedia.org/wiki/File:
Govt_bridge_anim1.gif
Vertical Lift Bridges
http://en.wikipedia.org/wiki/File:
MovableBridge_lift.gif
http://en.wikipedia.org/wiki/File:
SteelBridgeOpen1.jpg
Other Structures
Drainage Structures
Retaining Walls
Tunnels
Sheds
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.
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.
Retaining Walls
Gravity
Retaining
Wall
http://www.concretenetwork.c
om/concrete/poured_concrete
_retaining_walls/semi_gravity.
htm
Sheet Piling
Crib Wall
http://slopes.jkr.gov.my/Photos/Treat
ment/pages/Crib%20Wall%201.htm
http://www.p3planningengineer.com/pho
to%20gallery/machines/piling%20and%20
diaphragm%20wall/piling%20and%20diap
hragm%20wall.htm
Retaining Walls
MSE
http://www.freepatentsonline.com/71252
02-0-large.jpg
http://www.gemtec.ca/gallery/photo04.jpg
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.
Tunnels
Rock cut tunnels
Soft ground tunnels
http://ghostdepot.com/rg/mainline/san
%20juan%20branch/toltec.htm
http://subaus.org/wpcontent/uploads/2008/08/sandhogs750.jpg
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.
http://www.modvid.com.au/html/body_jim_vail.html
Questions?
?snoitseuQ
Thank You