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CEE 412 Flashcards

1
Q

What is railway track engineering?

A 
Engineering discipline engaged in planning, design, 
construction,
inspection,
Maintenance,
Advancement of track structure
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2
Q

Evolution of track structure

A 
Has evolved over past 200 years
Changes often to increase train loads and speed
Trial and error approach
Analytical approach began end 1800s
Modern: mechanistic design
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3
Q

Primary function of track

A 
Support and distribute train loads
Guide the vehicle
Provide adhesion at wheel-rail interface
Provide smooth running surface
Facilitate drainage
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4
Q

Secondary function of track

A

Transmission of signal circuit
Broken rail detection
Path of ground return for traction power

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5
Q

Track engineering fundamental

A

Providing adequate drainage

Where does the water go

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6
Q

Track components

A 
Welded rail
Crosstie
Fastener
Tie plates
Spikes
Rail anchors

Rail pads

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7
Q

Where is track gauge measured

A

distance between heads

5/8“ (15.875mm) below the top of the rail

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8
Q

Track gauge examples

A 
Spain, India 1767
Russia 1524
UIC 1435
South Africa, japan 1067
Switzerland, india 1000
Russia 750
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9
Q

Klingel Motion

Amplitude/Cycle length

A

Lk=2Pi sqrt(rs/2gamma)

y=y0sin(2pix/L)

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10
Q

Truck hunting

A

Lateral, side to side steering motion

Influenced by speed, carbody resonance, wheel conicity, rail head geometry, suspension

Can lead to excessive rail wear, wheel wear, wider gauge, derailment

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11
Q

Quasi static Forces acting on the track

A

Groß tare
Centrifugal
Wind

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12
Q

Dynamic forces acting on the track

A

Track irregularities
Discontinuities
Irregular running surface
Vehicle defects

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13
Q

Vertical forces acting on track

Similar for lateral

A

P total =

P static +
P centering (curvature,cant) +
P wind +
P dynamic

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14
Q

Longitudinal Force on track

A

Thermal force
Traction force
Braking force

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15
Q

Calculating dynamic wheel load

A

Dynamic load> static load

Pd = Ps + thetaPs

Impact factor theta:
33V[MPH]/(D[inches]100)

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16
Q

Size of a contact patch

A

1/2 sq. In.

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17
Q

Track performance requirements

A 
Stiffness
Resilience
Resistance to permanent deformation
Stability
Alignment and adjustability
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18
Q

Criteria for success

A

Safety

Cost:
Reliability, availability, maintainability

Comfort

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19
Q

Components of track superstructure

A

Rail
Ties (sleeper)
Fastening system

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20
Q

Components of track substructure

A 
Top Ballast
Bottom ballast
Subballast
Placed foil (fill)
Natural ground
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21
Q

Importance of the wheel-rail Interface

A

Low friction for efficiency

Strength to resist vertical forces

Wear and fatigue resistance for cost effective operation

22
Q

Key aspects of rail metallurgy

A 
Chemical composition 
Cleanliness of steel
Microstructure 
Hardness and wear resistance
Tensile properties
23
Q

Additional Chemicals in rail steel

Wanted or unwanted

A 
C
Mn
Si
S
P
Cr
V
24
Q

Definition: Hardness

A

The ability of a material to resist penetration, scratching, wear, abrasion and cutting

25
Q

Definition: ductility

A

The ability of a material to undergo relatively large plastic deformations before fracture

26
Q

Definition: toughness

A

The ability of a material containing a crack to resist fracture

27
Q

Key rail dimension

A

Head shaped to meet wheel contour

Broad base to resist overturning

Base shaped to facilitate fastening to ties

Web connects head and base

28
Q

Standard rail sections

A

136 RE. 136 lb/yd

UIC 60. 60 kg/m

29
Q

Typical hardness of rails

A

Measured in brinnel hardness:

200-240
…
350-390

30
Q

Continous welded rail

A

Welded to eliminate joints

Length > 400 feet
(200-800m)

Needs control of thermal stresses
Must be anchored

31
Q

Crosstie fundamentals

A

Maintain gauge

Distribute wheel loads from rails to ballast

Anchor track against lateral, longitudinal, vertical movement

Spacing: 18-30“

32
Q

Function of fasteners

A

Longitudinal resistance

Torsion resistance

Lateral, vertical flexibility

33
Q

11 Functions of ballast

A

Transmit and reduce tie pressure to subgrade

Anchor rail-tie structure

Absorb dynamic impact

Facilitate drainage

Provide dry support medium to prolong service life of ties

Facilitate maintenance

Reduce occurrence of track frost heave

Prevent vegetation growth

Provide voids for „storage“ of fouling material

Absorb noise and vibrations

Provide electrical resistance between rails

34
Q

Important ballast properties

A

Particle size, gradation, shape

Resistance to weathering, fragmentation, degradation

Compressive strength

Clean and cleanable

Workability for alignment adjustments

35
Q

Ballast material suitable for HSR

A

Crushed stone

  • granite
  • quartzite
  • basalt
  • traprock

(Hard, durable, good repeated load behavior)

36
Q

Sources of fouling

A

Ballast breakdown

  • handling
  • thermal stress
  • freezing water
  • tamping damage
  • Traffic damage

Infiltration from ballast surface

Tie (sleeper) wear

Infiltration from underlying Granulat layers

37
Q

Drainage requirements

A

Keep the ballast clean enough for water to drain as fast as it enters

Have the surface of the subballast and subgrade slopes away from the center of the Track

Provide a means for water coming out of the substructure to drain away from the track

38
Q

Design principle of slab track systems

A

Enough strength and stability: high safety

Reasonable design scheme of manufacturing, laying and fine-adjusting of track structure: smooth

Reasonable structure types and durable engineering material: low maintenance

39
Q

Classification of loads

Slab track

A

Dead load

  • structure weight
  • shrinkage
  • creep of concrete

Live load

  • vertical, lateral, temperature force
  • flexure of support

Additional loads

  • braking, traction force
  • uneven settlement of support layers

Special loads
- temporary construction forces

40
Q

Dynamic evaluation of slab track

A

Safety index

  • derailment coefficient
  • rate of wheel load reduction

Comfort index
- carbody acceleration

Dynamic response index

  • vertical, lateral force
  • acceleration
  • vibration, noise
41
Q

Typical uses for continous/discrete concrete bed structure

A

Cobtinous:

  • subgrade
  • tunnel sections

Discrete:
- bridges

42
Q

Technical features of pre-cast slab track

A

High concrete structure quality

Environmental and weather influence reduced

Allows scheduling efficiencies

43
Q

Advantages of ballasted tracks

A

Low initial construction cost

High elasticity

Simple maintenance at low cost

High noise absorption

Easier to renew on existing lines

Less complex drainage systems

Advanced maintenance techniques

44
Q

Advantages of slab track

A

Higher level of track stability

More precise control of alignment

Improved ride comfort

Longer life cycle

Minimal maintenance requirement

Higher availability

Reduced structural height

45
Q

Disadvantages of ballast track

A

Rate of geometry deterioration

Lower lateral track resistance

Fouled ballast inhibits drainage

Weight increases cost on bridges

Increased structural height

Ballast flight st high speed

46
Q

Disadvantages of slab track

A

Higher initial construction cost

Complexity of construction

Sensitivity to construction defects

Less long-term experience

More susceptible to settlement

Less sound & vibration absorption

47
Q

Decision between ballast/slab:

Operational concept

A

Availability for operations

Business case

Ride comfort requirements

48
Q

Decision between ballast/slab:

Production & maintenance concept

A

Maintainability

Possibility of making adjustments

Replacement investment requirement

Availability of component supplies

49
Q

Decision between ballast/slab:

Risks/ malfunctions

A

Safety

Pattern of damage & repair following derailment

Remediation of defects

50
Q

Decision between ballast/slab:

Miscellaneous requirements

A

Drainage

Structure-borne noise

Airborne noise

Effects on the subsoil

Clearance gauge

51
Q

What are the current types of slab track on the market?

A

Cast in site concrete

Precast concrete elements

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