noise & vibration mitigation in railway track · low-frequency excitations are difficult to...

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NOISE & VIBRATION MITIGATION IN RAILWAY TRACK

Coenraad EsveldEsveld Consulting Services

Emeritus Professor of Railway Engineering TU Delft

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Noise: Rolling; Engines; Curves; Braking; Aerodynamics.

Vibration: Rayleigh waves (at surface); Compression waves (tunnels); Shear waves (tunnels).

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CLASSIFICATION NOISE ANNOYANCE

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SQUEALING NOISE

Mitigating measures:• Lubrication;• Asymmetric rail grinding, shift of contact point wheel rail.

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CONTRIBUTION OF NOISE SOURCESTotal

Sleeper

Wagon

Rail Wheel

Sleeper

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METHODS OF NOISE REDUCTION Track Design

– Component selection (pads/sleepers)

– Embedded rail/special slabtracks– Damping

Barriers– Up to 10dB but affected by layout

of tracks/buildings– Expensive & visual impact– Low barriers & shrouds: not

interoperable

Acoustic grinding– Effective for corrugation– Not so effective for tracks in good

condition Absorptive Layers

– Low results on the rail– Higher results on slab track -

absorbs wheel noise Vehicle Design

– Wheel diameter– Wheel damping

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ENERGY DISTRIBUTED IN STRESS WAVES:

Rayleigh 67 % Shear 26 % Compression 7 %

GeometricalDamping Law

Vibrating source

Horiz.Comp.

RelativeAmplitude

Shear Wave

ν = 0.25

ShearWindow

GeometricalDamping Law

R-1

++

+ +

+

––

Compression wave

R-1

R-2 R-2 R-0.5

Rayleigh WaveVert.Comp.

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VIBRATION PROPAGATION AT GRADE

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VIBRATION PROPAGATION BY UNDERGROUND

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The human body is susceptible to the following frequencies: 0.1 - 0.2Hz : resonance of the organ of balance, resulting in

phenomena characteristic of seasickness; 4 - 8 Hz: resonance of the contents of abdomen and

thorax; 30 - 80 Hz: resonance of eyes in the eye sockets,

resulting in loss of focus;

The audibility limit lies at a frequency of approximately 20 Hz.

SUSCEPTIBILITY OF HUMAN BODY

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RVES

OF

EQU

ALVI

BRAT

ION

PERC

EPTI

ON

rms2

0.18 fEP v ( f )f1

5.6

= +

peak rmsv 2v=

2a 2 fv ( 2 f ) dπ π= =

102

101

8

5

3

2

8

5

3

2

100

8

5

3

2

10-1

101

100

10-1

5

3

2

8

5

3

2

8

5

3

2

8

Vibr

atio

n ve

loci

ty (r

ms-

valu

e) [m

m/s

]

Vibr

atio

n ve

loci

ty (p

eak

valu

e) [m

m/s

]

EP = equal perception

EP = 25.6

EP = 12.8

EP = 6.4

EP = 3.2

EP = 1.6

EP = 0.8EP = 0.56EP = 0.4

EP = 0.28

EP = 0.2

EP = 0.14

EP = 0.1

521 10 5020 100Frequency f [Hz]

Not noticeable

Very weak

Weak

Good

Strong

Very strong

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CLASSIFICATION OF VIBRATION LEVELS

ISOGERMANYReference v0not standardized LEP [dB] = 20 log10(v/v0), with for instance v0 = 10-8 m/s

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MEASURED VIBRATIONNEAR UNDERGROUND

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EFFECT OF HIGH-SPEED MEASURED AT DB

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mw cw kw F ( t )+ + =

( ) ( ) ( )π

≈

= =

1 kf2 m

K kw f F f H fTransmission Ratio

Mitigating measures:• Reduce force, cq excitation:

grinding, weld straightening;• Change natural frequency relative to

dominant excitation frequency:softer rail pads, resilient layers, …….

VIBRATION TRANSFER

k c

m

w

Fexcitation

Kresponse

10.00

1.00

0.10

0.01 0.1 1.0√2 10.0

f = excitation (impressed) frequency [Hz]f/fn

trans

mis

sion

ratio

|K(f)

/F(f)

|

ζ = 1.0

ζ = 0.5

ζ = 0.2

ζ = 0.1 ζ ζ = 0

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Dom

inan

t exc

itatio

n fre

quen

cy

Natu

ral f

requ

ency

stru

ctur

ef

f

f

1

→X

→=

Excitation spectrum

Transfer function

Response spectrum

VIBRATION TRANSFER II

excit naturalf 2 f>

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Low-frequency excitations are difficult to reduce

1 kf2 mπ

≈

Low stiffness and large mass necessary to achieve low frequency! Not with sleeper and rail pad, but with elastically supported slab.

PRACTICAL LIMITS

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Cork rubberConcrete block

Casting

BLOCK TRACK

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STEDEF

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PANDROL VANGUARD

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WHISPER RAIL THYSSENKRUPP

Vertical up to 10 mm Lateral < 2 mm

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KÖLNER EI

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ELASTIC RAIL SUPPORT

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SA 42 RAIL LOW NOISE -5 dB(A) compared to

ballasted track -7 dB(A) compared to

conventional slab track 60 % less consumption of

corkelast compared to UIC 54

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EMBEDDED RAIL ON STEEL BRIDGE

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SILENT BRIDGE WITH EMBEDDED RAIL

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SILENT BRIDGE VERSUS CONVENTIONAL

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CAST-IN SLEEPER

Ballast

Elastic supported sleeper

Polyurethane

Reinforced concrete

Filler concrete

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TRACK ON ELASTICALLY SUPPORTED SLAB

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GERB Floating Slab Track Systems

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Wege für MenschenUSP – Under Sleeper Pads

UNDER SLEEPER PAD (USP)

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UNDER SLEEPER PADS (USP) Increase of contact area between concrete and ballast (Riessberger): 5-10 % without USP ~ 35 % with USP

Adding resilience and thus reducing dynamic forces Very effective in areas with high impact forces: frog area of turnouts; transitions near engineering structures;

Effective solution at spots with maintenance problems due to poor subgrade;

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CONCLUSIONS Apply mitigating measures preferably at the source: smooth wheel-rail interface; sufficient track resilience;

Reduction of natural frequency: low spring stiffness; large mass;

1 kf2 mπ

≈