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Chapter 23

Concrete & Other

Artificial Ties

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Types of ties

Timber Concrete

Plastic (and composite) Steel

2

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Concrete

Early Use

Problems (not pre-stressed)

After World War II

Pre-stressed Designs Revised Specs

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Concrete Cross Ties (Monoblock)

Precast, pre-stressed concrete

Effective for high tonnage or high speed track

Elastic fastener systems of various designs

Vulnerable to mechanical damage, rail seat abrasion,effects of poor subgrade

Must insulate in track circuit territory

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Typical Concrete Tie

~ 2 1/2 times heavier than wood ties,More expensive than wood ties

Pre-cast, Pre-Stressed, elastic fastenings embedded

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Turnout

Highway Crossing

Surface

Tie Manufacturer

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Fastenings

Recent Experience

Economics ???

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Epoxy Repair of Concrete Tie Rail

Seat Deterioration

Wear and Abrasion

Some Problems with Concrete Ties

Pumping Track (stiffer track compared to

wood tie track, need quality support for

concrete tie track)

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Concrete Tie Pads

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Recent Experiences with Concrete Ties

Need high-quality subgrade for support

Pressures on ballast are higher under concrete ties

compared to wood ties

Concrete tie track produces stiffer(higher

modulus) track compared to wood tie track

Rail-Seat abrasion and insert problems

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AREMA Manual

Performance Specifications

Tie Spacing wider than wood ties

Tie Dimensions slightly larger than wood ties

Load Distribution higher ballast pressure

Impact Factor higher than for wood ties

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55%

For 27-inch

tie spacing

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Ballast Pressure

Subgrade Pressure

Lateral & Longitudinal Loads

Rail Flexure

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Concrete Properties very high strength

Pre-tensioning Tendons typically 270 kip

Tie Pads -- important

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Steel

Two-Block Concrete/Steel

Plastic

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Steel Ties

Rolled channel shape with downturned ends

Elastic fastener systems of various designs

Track stiffness comparable to timber ties Poor for wet or corrosive environments

May abrade soft ballast materials

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Alternate Concrete Tie

Two-Blockor

Bi-Block

With

Steel Beam

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Reconstituted/Laminated Wood

Slab Track

Azobe & Mora Wood

Plastic

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Concrete Slab Track

Direct Fixation

Ballastless Track

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Azobe Hardwood Ties

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Plastic Ties Attractive in areas where timber is decay prone

In-track behavior similar to timber

Compatible with timber tie handling and installation

equipment

Compatible with fasteners used for timber Pre-drill fastener holes to avoid splitting tie

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30

First Steel Reinforced Plastic Bridge Ties installed in American railroading.

Bridge P 424.8 Leeds, AL May, 2005 Manufactured by Plastic Pilings.

An additional 1000 ties will be installed in 2006

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31

BURKE PARSONS BOWLBY PARRALAM DECK

LUMBER CITY, GA