IN THIS ISSUE
Big Data: Predicting maintenance using
technology to keep assets moving
The Virginia Railway Express: Regional
benefits of the commuter rail system
Assessing safety issues and challengesof long freight trains for Europe

ISSUEFEB01 2018

EXPERTISE| OPINION | INTELLIGENCE

globalrailwayreview.com

Middle East developments
Exploring Saudi Arabia’s network development
programme plus analysis of the Gulf Railway Project’s
latest regulation and legislation progress

FORMERLYINFRASTRUCTURE

Measuring the vibration-isolatingeﬀect of an elastic railway
superstructure in Poland
The Railway Institute at Wrocław University of Science and Technology has
convincingly demonstrated the value of the cost-effective type SLS1308G undersleeper pads used on the Kraków Airport rail link in Poland.
Here, Ewelina Kwiatkowska, Adjunct Professor at Wrocław
University of Technology, together with Getzner Werkstoffe
colleagues Harald Loy (Head of R&D, Railway Division) andMichael Biskup (Project Manager), explore the requirements,performance of measurements and results of the project.
Requirements of elastic under sleeper pads

Railway line ‘118’, run by the Polish state rail
operator PKP PLK, connects Kraków Central
Station to Kraków Airport and was modernised in2015. The track’s superstructure largely consistsof type 60E1 rails, elastic rail fastening systems
on type PS94 concrete sleepers, and a 30cm layerof ballast. Approximately 12,000 under sleeper
pads have been installed in several sensitive
sections of track, with requirements being set out
in the ‘PB Uklad torrowy i podtorze’1 tender text:‘To reduce negative influences on the surroundings(reduction of disruptive vibrations) pads should beused under the sleepers of new sections of track.
These should represent a cost-effective alternative
to under ballast mat solutions…In addition to
reducing vibrations emitted to the surroundingarea, the use of under sleeper pads can also
reduce dynamic forces’.
SLS1308G under sleeper pads from Getzner
Werkstoffe were selected. By using thesecost-effective and highly efficient polyurethane

42products, the rail operator aims to significantly
reduce emissions to the surrounding environment
by making use of the physical principle of vibration
isolation. Furthermore, less noise and fewer
vibrations should be emitted due to improved
long-term trackbed behaviour, allowing trains torun more smoothly. In general, the effectiveness ofelastic components in the railway superstructureis dependent on variables such as mass, stiffnessand damping. The technical material Sylomer® has
become an established cushioning component for
the reduction of emissions.
Not all under sleeper pad products are the same.
The dynamic stiffness and long-term behaviour are
two crucial factors. It is only possible for padded
sleepers to yield their full vibration-isolating effecton the track if the superstructure behaviour has
been precisely calibrated to the application athand. Although a higher dynamic efficiency of thechosen polyurethane material (PU) also increases
the vibration protection performance, correctly
calculating the design of the entire system (including

HARALD LOY is Head ofR&D in the Railway Divisionat Getzner Werkstoffe. He
graduated from the Technical
University of Munich witha degree in Civil Engineeringand holds a doctoral degreein Railway Engineering fromthe University of Innsbruck.
After being employed in thecomputer industry, Harald
has been working as a System
Engineer since 2005, witha focus on simulation,
laboratory testing and in-situ
measurements of elastic
track applications. He is
author of over 30 papers,
patents of inventions andtechnical notes published onnational and international
congresses and journals.

globalrailwayreview.com

GLOBAL RAILWAY REVIEW | Volume 24, Issue 01

taking consideration of the rail vehicles used on therespective track section) is crucial. The elastically
optimised airport track is predominantly served bytype EN77 trains travelling at frequent intervals andat an average speed of 70km/h.

FIGURE 1Measurements on the airport link

Measurements were performed on 14 September
2016 on two track sections1, one of which
was equipped with under sleeper pads, while
the reference section had a conventional
ballasted track:●●

Section 1 without sleeper pads: 3,700km(±100m), track number ‘1’ left section
Section 2 with sleeper pads: 3,500km(±100m), track number ‘1’ right section.

Firstly, the vertical deflections were measured
as a train passed over specific sleepers to
obtain a representative picture. In the unpadded
section, these exhibited a very stiff behaviour;
the vertical movement measured was onlyapproximately 0.3mm. However, in the track
section with under sleeper pads, a far moreelastic behaviour was identified. Verticaldeflections of approximately 1.5mm confirmed
the mathematical predictions. These resultsmean that a reduction in the propagationof disruptive vibrations can be expected.
With enhanced track elasticity the dynamic
forces are reduced and the ballast is protected.
This improves the long-term quality of therailway superstructure.
The vibration measurements were performed
with acceleration sensors on driven piles nextto the track at three measurement points
in the unpadded section and three in thepadded section (distance from track centre
6-8m, measurement point spacing in thetrack’s longitudinal direction 25m). A total of
12 passing trains were recorded dynamically
FIGURE 2

at each point. Measurements were taken andevaluated in accordance with relevant standards
that apply to elastic elements in the railway
superstructure2,3.
The frequencies can be seen in the one-thirdoctave band diagram shown in Figure 4.
The difference spectrum demonstrates theeffectiveness of the under sleeper pads throughwhat is known as insertion loss. The insertion
loss describes the relative effect of the mitigation
measure compared with the reference situation3.
It shows how the one-third octave band
spectrum of structure-borne noise changes if
under sleeper pads are installed, as in this case.
Ideally, all other emission influences remain
constant here; for example, the same vehicle,
the same speed and identical rail roughness,
etc. are considered. As the elastic element
influences the railway system as a whole, thefrequency-dependent insertion loss may varywith other track superstructure properties, othersubsoils and/or other vehicle types.

ABOVE: Under sleeper
pads made fromSylomer® were used

MICHAEL BISKUP is
currently working as ProjectManager for the construction
and rail sectors at Getzner
Werkstoffe. After studying
engineering at the Technical
University of Berlin,
Michael initially worked asa Construction Manager andlater Project Manager ona large construction site
at Potsdamer Platz inBerlin. Since 1999 Michael
has been in charge ofdemanding and challenging
building bearing projects inGermany and is presently
responsible for market
development and project
management in the railway
sector, both in theNetherlands and in Poland.

LEFT: Measuring on line
‘118’ with and without
under sleeper pads
@GlobalRailway

43

INFRASTRUCTURE

RIGHT: Sleeper
deflections without(left) and with undersleeper pads (right) at
measuring point 1

EWELINA KWIATKOWSKA
is a graduate in Civil
Engineering from theWrocław University ofScience and Technology andis currently working there
as an Adjunct Professor.
For 10 years Ewelina
was associated with thescientific and research
work of railway surfaces
and is a known specialist inscientific research in railway
vibration and noise. After
graduating with a masterof law from the University ofWroclaw, Ewelina worked forthe office of rail transport,specialising in the procedureof technical approvals
for building materials on
Polish railway lines.

BELOW RIGHT:
Measured one-thirdoctave band of thevibration velocities withand without SLS1308G
under sleeper pads (left)
and associated insertion
loss as a difference
spectrum (right)

FIGURE 3

Vibration reduction of up to 74 per cent

The insertion loss is shown in Figure 4 as thedifference between section 1 (without undersleeper pads) and section 2 (with under sleeperpads), expressed in decibels (dB). Positive dB-values
represent a reduction in vibrations, due to theimprovement of the track superstructure. As canbe seen from the measured insertion loss, thevibrations in the track with under sleeper pads are
reduced at frequencies above 31.5Hz comparedto the track without any additional elastic
polyurethane elements. Frequencies from 40Hz
to 200Hz are primarily responsible for secondary
airborne noise in adjacent buildings.
To highlight some specific results: Vibrations
between 50Hz and 63Hz yield a sound level of80dBv without under sleeper pads, while the levelwith under sleeper pads is reduced to less than69dBv at train speeds of 70km/h. The dominant
one-third octave band of passing trains cangenerally be found at approximately 63Hz. The useof type SLS1308G under sleeper pads results in
an insertion loss of 11.6dB, which is equal to an
average vibration reduction of 74 per cent. In

the natural frequency range only a very small
resonance amplification can be seen. Theseinvestigations, especially at the relevant frequency
range of 63Hz, demonstrate the fundamental
suitability of under sleeper pads in reducing
vibrations and secondary airborne noise.

Summary and conclusions

The aim of this study was to quantify thevibration-isolating effect of under sleeper pads
in ballasted track. The measurements wereperformed on the Kraków Airport rail link inPoland. The insertion loss shows that the use ofelastic under sleeper pads made from Sylomer®
significantly reduces the transmission ofvibrations. At a frequency of 63Hz in the one-thirdoctave band an average insertion loss of 11.6dB
was measured, which is equal to a 74 per centreduction in vibrations. In addition to the described
effect of vibration mitigation, the use of undersleeper pads also improves the long-term qualityof the railway superstructure. The results are lower
maintenance efforts and thus lower costs andhigher availability for the railway operator.

FIGURE 4

REFERENCES
1.

Kwiatkowska E. Measurement
results of vibration isolation
performance, under sleeper pads
SLS1308G at Krakow Lobzow.
Wrocław University of Scienceand Technology, Report No.
126/2017.

2.

DIN 45669: Measurementof vibration immission,
DIN 45672: Vibration
measurement associatedwith railway traffic systems.

3.

DIN 45673-3: Mechanicalvibration – Resilient elements
used in railway tracks – Part
3: Experimental evaluationof insertion loss of mounted
track systems.

44globalrailwayreview.com