CE 515 Railroad Engineering

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CE 515 Railroad Engineering

Structures

Source: AREMA Ch. 8.3,8.4



“Transportation exists to conquer space and time
-


Bridge Types

Timber Trestles

Picture
sources:
http://me
mbers.cox.
net/sn3nu
t/trestles%
20part%20
1.htm

Steel Bridge

Picture
Sources
:
http://u
pload.w
ikimedi
a.org/w
ikipedia
/comm
ons/8/8
5/Forth
railbrid
gefroms
outhqu
eensfer
ry.jpg

http://f
arm1.st
atic.flick
r.com/2
25/493
880918
_adc1e
46808.j
pg

Concrete Bridges

http:/
/en.wi
kipedi
a.org/
wiki/Fi
le:Peg
asus_
bridge
_new.j
pg

Moveable Spans

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
.




Picture sources:
http://clevelandsteel.thomasnet.com/category/shea
r
-
plates
-
split
-
rings
-
spike
-
grids

Spike Grid Timber Connector

Split Rings

Picture sources:
http://members.cox.net/sn3nut/trestles%20part%2
01.htm

Steel Bridges

From short simple
beam spans to large
through trusses.


Ease of construction
and maintenance
under traffic


Spans could be
cascaded to different
location.



The forth railway bridge is the most famous
bridge in Scotland. Constructed in 1890 it was
the world first major steel bridge.




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, 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 .






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

Pictures source: http://okbridges.wkinsler.com/technology/index.html

Schematic diagram of a through Pratt truss, illustrating the various members and their
names. Members in compression are in heavy lines, tension in light

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://okbridges.wkinsler.com/builders/oklahoma.h
tml

http://data2.collectionscanada.gc.ca/ap/a/a029691.jpg

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.





Concrete Bridges

http://switzerlandinview.wordpre
ss.com/2007/10/29/landwasser
-
viaduct/

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

Rolling

Lift

Heel

Trunnion






http://en.wikipedia.org/wiki/File:
Mystic_River_Bridge.jpg

http://en.wikipedia.org/wiki/File:
MovableBridge_draw.gif

http://en.wikipedia.org/wiki/File:
MovableBridge_roll.gif

http://en.wikipedia.org/wiki/File:
Pegasus_bridge_new.jpg

http://etc.usf.edu/clipar
t/6200/6259/bridge_8.
htm

http://en.wikipedia.org/wiki/File:
Lake_Erie_Drawbridge.JPG

Moveable Spans


Swing

Span

Bridges

Vertical

Lift

Bridges

http://en.wikipedia.org/wiki/File:
MovableBridge_swing.gif

http://en.wikipedia.org/wiki/File:
MovableBridge_lift.gif

http://en.wikipedia.org/wiki/File:
SteelBridgeOpen1.jpg

http://en.wikipedia.org/wiki/File:
Govt_bridge_anim1.gif

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

http://www.concretenetwork.c
om/concrete/poured_concrete
_retaining_walls/semi_gravity.
htm

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

Gravity
Retaining
Wall

Crib Wall

Sheet Piling

Retaining Walls

http://www.gemtec.ca/gallery/photo04.jpg

http://www.freepatentsonline.com/71252
02
-
0
-
large.jpg

MSE

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

http://ghostdepot.com/rg/mainline/san
%20juan%20branch/toltec.htm

Rock cut tunnels

Soft ground tunnels

http://subaus.org/wp
-
content/uploads/2008/08/sandhogs750.jpg

Sheds

http://www.modvid.com.au/html/body_jim_vail.html

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.

Questions?

?
snoitseuQ

Thank You