Creep of Rails in Train Tracks
Numerical Example
Numerical Example
Numerical Example
Numerical Example
What should be the length of track to overcome temperature stress if rise
in temperature
t = 30 °C
Assume 700 kg as resistance to track movement.
Given:
A= 60 cm
2
,
𝜶 = 1.15 x 10
-5
per, °C and E = 21.5 x 10
5
kg/
cm
2
Creep of Rails
Creep of Rails
Creep of Rails
Creep of Rails
is defined as the longitudinal movement of rails with
respect to sleepers in a track.
There are mainly six causes (mechanisms) behind creep
defect:
o
Wave action.
Wave action.
o
Percussion action.
Percussion action.
o
Drag action.
Drag action.
o
Starting, accelerating, slowing, or stopping of a
Starting, accelerating, slowing, or stopping of a
train.
train.
o
Expansion or contraction of rails due temperature.
Expansion or contraction of rails due temperature.
o
Unbalanced traffic.
Unbalanced traffic.
Why Creep Takes Place?
Why Creep Takes Place?
Wave Action
Wave Action
According to the
wave theory
wave theory
, the rail creep is caused due to
formation of
formation of
the crest curve
the crest curve
ABC
ahead
ahead
of the wheels, as the result of
deflection under
deflection under
load
load
. The wheels
push the rails
push the rails
in the
direction of train movement
direction of train movement
, causing
creep. The rear crest gets back to its normal position.
Reducing wave action will reduce creep. This can be achieved by
increasing the track stiffness:
Use ballast with good interlock (angular in shape).
Larger rail section.
Closer sleeper stiffness.
Percussion Action
Percussion Action
Creep occurs due to impact load (R) of wheels at the rail end at
joints.
Horizontal component of the load (P) pushes rails in the direction of
train movement, causing creep. Next wheel will do the same
(cumulative creep effect)
Dragging Theory
Dragging Theory
Wheels of moving locomotive tends to push rails backward, while
moving railcars pushes rails forward (due to wave action).
Pictures adapted from:
http://www.studylecturenotes.com/
engineering/transportation-engineering/161-what-is-creep
When train starts its journey,
the wheels pushes the rail
backward [direction of creep
is backward].
When brakes are applied at
the end of the journey,
wheels of the rail cars tend
to push the rail track in
forward direction [direction
of creep is forward].
Starting, Accelerating, Slowing
Starting, Accelerating, Slowing
or Stopping train
or Stopping train
Expansion or Contraction of Rails
Expansion or Contraction of Rails
Due to Temperature Change
Due to Temperature Change
KSA environmental conditions! Class discussion
Unbalanced Track
Unbalanced Track
In
a single line
system if heavy
equal traffic (load magnitude and
repetition) runs both direction, the
creep will be balanced. BUT if train
runs full in one direction and
empty when back, the creep is
unbalanced.
How it works if
double track
system was the case?
Creep of rails refers to the longitudinal movement of rails due to various factors like wave action, percussion action, dragging theory, and train movement. This movement can lead to track instability if not properly managed. Understanding the causes and effects of rail creep is crucial for maintaining safe and durable railway infrastructure.
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Presentation Transcript
Numerical Example What should be the length of track to overcome temperature stress if rise in temperature t = 30 C Assume 700 kg as resistance to track movement. Given: A= 60 cm2, ? ? = 1.15 x 10-5 per, C and E = 21.5 x 105 kg/ cm2
Creep of Rails Creep of Rails is defined as the longitudinal movement of rails with respect to sleepers in a track. Why Creep Takes Place? There are mainly six causes (mechanisms) behind creep defect: o Wave action. o Percussion action. o Drag action. o Starting, accelerating, slowing, or stopping of a train. o Expansion or contraction of rails due temperature. o Unbalanced traffic.
Wave Action Train Movement According to the wave theory, the rail creep is caused due to formation of the crest curve ABC ahead of the wheels, as the result of deflection under load. The wheels push the rails in the direction of train movement, causing creep. The rear crest gets back to its normal position. Reducing wave action will reduce creep. This can be achieved by increasing the track stiffness: Use ballast with good interlock (angular in shape). Larger rail section. Closer sleeper stiffness.
Percussion Action Creep occurs due to impact load (R) of wheels at the rail end at joints. Horizontal component of the load (P) pushes rails in the direction of train movement, causing creep. Next wheel will do the same (cumulative creep effect)
Dragging Theory Wheels of moving locomotive tends to push rails backward, while moving railcars pushes rails forward (due to wave action). http://interfacejournal.com/wp-content/uploads/2014/05/ryan1.jpg Rail cars Wave action effect Greater than the Locomotive Drag effect
Starting, Accelerating, Slowing or Stopping train Train Movement When train starts its journey, the wheels pushes the rail backward [direction of creep is backward]. Direction of Creep Starting Train Train Movement When brakes are applied at the end of the journey, wheels of the rail cars tend to push the rail track in forward direction [direction of creep is forward]. Direction of Creep Stopping Train Pictures adapted from: http://www.studylecturenotes.com/ engineering/transportation-engineering/161-what-is-creep
Expansion or Contraction of Rails Due to Temperature Change Increase of temperature Rails creep both sides Decrease of temperature KSA environmental conditions! Class discussion
Unbalanced Track http://thumbs.dreamstime.com/z/unbalanced-concept-depicted-help-seesaw-having-golden-silver-ball-35974043.jpg In a single line system if heavy equal traffic (load magnitude and repetition) runs both direction, the creep will be balanced. BUT if train runs full in one direction and empty when back, the creep is unbalanced. How it works if double track system was the case?
