Design of Roadways, Railways & Guideways - Sections & Intersections Presentation - Part 3

7/28/2019 Design of Roadways, Railways & Guideways - Sections & Intersections Presentation - Part 3

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PRESS ENTER TOSTART!


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QUOTABLEQUOTES

A person that values its privileges

above its principles soon loses both."- Dwight D. Eisenhower

(1890-1969)


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There are six main elements of railroad cross section:

oBallast

oCrosstiesoTie Plates

oFastenings

o

Rail AnchorsoRail Joints


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BALLASTTrack ballast is a key structural element of the railroad permanent way. Its prime

function is to transmit & distribute the wheel loadings from the base of the crossties to

the subgrade. It also serves as anchor the track, preventing longitudinal & transverse

movement.

Open graded materials that can perform satisfactorily the required functions of ballast are

crushed stones, washed river or pit run gravel & furnace slags. Typically, the material size

varies from 1 to 1 in.

Depth of the ballast may vary from 6-30in or more depending on the wheel load, traffic

density & speed, type & condition of foundation.

QUALITY STANDARD OF BALLAST:

1. Wear Resistance abrasion test, wear of any ballast material is limited to 40%

2. Cleanliness

3. Frost Resistance

4. Unit Weight

compacted weight of not less than 70

100 lb/ft

3

.


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BALLAST


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CROSSTIES

The crosstie serves several functions, including:

1) Spreading horizontal & vertical loadings to ballast

2) Maintaining correct gauge between the rails

3) Providing, in conjunction to ballast

4) Providing a convenient means of making needed vertical adjustment

Typically made up of wood which is treated with both preservative & coating materials for

protection against weathering & splitting while in service.

Sizes are 6in thick x 6in wide to 7in thick x 9in wide. Tie lengths also vary, standard sizes

are 8, 8.5 & 9ft long.

Tie replacement averages about 3% of all ties yearly.


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RAILS


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TIE PLATES

The rail is laid on tie plates that are secured to the crossties by spikes or other

types of fastening.

3 Principle Functions of Tie Plates:

1) To prevent damage to the wood crosstie by distributing the wheel loads over a largerarea.

2) To help hold the rail to proper gauge.

3) To partially offset the outward lateral thrust of the wheel loads by tilting the rails

slightly inward.

Tie plates are typically 7-8in wide, 10-14in long & 9/16 to 1in thick.

Special rubber/ plastic pads are sometimes placed between tie plates & crossties to

reduce tie wear.


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TIE PLATES


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FASTENINGS

Types of fastenings may be used to secure tie plates including common cut

spikes, spring spikes, screw spikes, compression clips & clamps.


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RAIL ANCHORS

They are used to reduce or stop longitudinal movement of rails. Their main

purpose is to hold the rail in a fixed position.


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RAIL JOINTS

Rail joints are used to provide smooth continuity of alignment & surface where

two rails ends meet & to transfer the wheel load from one rail to the other.


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FUN FACTS & TRIVIASRetaining walls are most often used to:

A) provide foundation for buildings

B) hold back the earth from a building or other structure

C) divide businesses from residential areas

Ans. B and maybe A. A retaining wall holds

soil, such as a basement wall. Although, it is

possible to make it integral with the

foundation for structures like a home.


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The EndProDeo, Familiaet Patria

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Design of Roadways, Railways & Guideways - Sections & Intersections Presentation - Part 3